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Synlett
Journal Prestige (SJR): 0.83

Citation Impact (citeScore): 2
Number of Followers: 43

Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0936-5214 - ISSN (Online) 1437-2096
Published by Thieme Publishing Group

[233 journals]

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  Synlett 2023; 34: VII-
  DOI: 10.1055/s-0043-1763654
  
  Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany
  
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  Inhaltsverzeichnis
  Synlett 2023; 34: VII-2023-11-29T09:54:26+0100
  Issue No: Vol. 34, No. 20 (2023)
Special Issue dedicated to Prof. Hisashi Yamamoto
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  Synlett 2023; 34: III-IV
  DOI: 10.1055/s-0043-1763655
  
  Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany
  
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  Synlett 2023; 34: III-IV2023-11-29T09:53:34+0100
  Issue No: Vol. 34, No. 20 (2023)
Regio- and Stereoselective Synthesis of 2′-Deoxy-4′-thioguanine
Nucleosides: Evaluation of Anti-Hepatitis B Virus Activity and
Cytotoxicity Leading to Improved Selectivity Index by 4′-C-Cyanation
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  Authors: Kumamoto; Hiroki, Imoto, Shuhei, Kuwata-Higashi, Nobuyo, Mitsuya, Hiroaki, Haraguchi, Kazuhiro
  Abstract: An N 9-regio- and β-anomer-selective 4′-thioglycosidation of purine bases has been developed. The reaction between a 2-deoxy-2-iodo-4-thioribofuranosyl glycosyl donor and N-(6-chloro-9H-purin-2-yl)-2-methylpropanamide gave the corresponding 2′-deoxy-4′-thiopurine nucleoside in 87% yield along with its N 7-regioisomer in 6% yield, without the formation of the α-anomer. By using a derivative obtained from 17, a practical chemical synthesis of 2′-deoxy-4′-thioguanosine was developed. 4′-α-C-Cyano-2′-deoxy-4′-thioguanosine was synthesized, starting from a 4-(acetoxymethyl)-2-deoxy-2-iodo-4-thioribofuranose derivative as a glycosyl donor. An evaluation of the anti-hepatitis B virus (HBV) activity and the cytotoxicity toward the host cell revealed that 4'-C-cyano-2'-deoxy-4'-thioguanosine exhibited about 100 times more potent anti-HBV activity than 2′-deoxy-4′-thioguanosine with a comparative cytotoxicity, resulting in the identification of a novel molecule having better selectivity index value than that of 2′-deoxy-4′-thioguanosine. This finding might provide a guideline for the development of the next generation of anti-HBV agents.
  Citation: Synlett ; : -
  PubDate: 2023-12-05T09:12:09+0100
  DOI: 10.1055/s-0043-1763629
Internal Atom Exchange in Oxazole Rings: A Blueprint for Azole Scaffold
Evaluation
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  Authors: Spinnato; Davide, Leutzsch, Markus, Wang, Feng, Cornella, Josep
  Abstract: In this article, we provide a route to transform isoxazoles and oxadiazoles into the corresponding pyrazoles and 1,2,4-triazoles in one step using catalytic amounts of an air-stable Ni(0) complex. The reaction is a formal atom-exchange process at the internal heteroatoms of the aromatic cycle. This work provides a blueprint for reactivity that permits the rapid evaluation of different five-membered azole scaffolds, thus avoiding de novo synthesis of the molecule of interest.
  Citation: Synlett ; : -
  PubDate: 2023-12-04T13:01:31+0100
  DOI: 10.1055/a-2201-9285
Quinolinamide-Enabled Nickel-Catalyzed Regio- and Diastereoselective
γ,δ-Arylalkylation of Nonactivated Alkenes
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  Authors: Zhang; Lanlan, Zhao, Lei, Zhu, Yuqin, Wang, Chao
  Abstract: A quinolinamide-enabled nickel-catalyzed γ,δ-arylalkylation of homoallylic amines with aryl iodides and organozinc compounds has been developed. The cleavable quinolinamide directing group facilitates the stabilization of a five-membered nickelacycle, and enables the dicarbofunctionalization of nonactivated alkenes with excellently regio-, chemo-, and diastereoselectivity. The reaction with internal alkenes proceeds stereospecifically to provide valuable γ-alkyl-δ-aryl-substituted amines with two vicinal stereocenters. The scope of substrates and the utility of the protocol have been thoroughly studied.
  Citation: Synlett ; : -
  PubDate: 2023-12-04T11:45:35+0100
  DOI: 10.1055/a-2192-7085
Lewis Base/3d Transition-Metal Cooperatively Catalyzed Asymmetric
Reactions
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  Authors: Song; Jin, Gong, Liu-Zhu
  Abstract: Lewis base/transition-metal cooperatively catalyzed asymmetric transformations have attracted extensive attention as they offer complementary catalytic systems within the realm of cooperative catalysis. Recently, the synergistic use of Lewis bases in combination with earth-abundant 3d metals has emerged as a fascinating prospect, presenting an opportunity to move away from the reliance on noble metals and to explore novel catalytic processes. In this Account, we highlight our recent achievements regarding the chemistry and synthetic utility of isothiourea (ITU) activated C1-ammonium enolates and N-heterocyclic carbene (NHC)-bound homoenolate equivalents in conjunction with 3d transition-metal activated electrophiles. The remarkable success in the stereoselective construction of carbon–carbon and carbon–heteroatom bonds has led to significant contributions to stereodivergent synthesis.1 Introduction2 ITU/Copper Cooperative Catalysis3 NHC/Copper Cooperative Catalysis4 NHC/Nickel Cooperative Catalysis5 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-12-01T10:38:54+0100
  DOI: 10.1055/a-2192-9185
Synthesis and Evaluation of 3′-Oleyl–Oligonucleotide Conjugates as
Potential Cellular Uptake Enhancers
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  Authors: Navarro; Natalia, Serantes, Sergio, Aviñó, Anna, Fàbrega, Carme, Eritja, Ramon
  Abstract: The field of therapeutic oligonucleotides has experienced significant growth in recent years, both in terms of approved drugs and those undergoing clinical trials. This expansion has transformed it into a rapidly evolving area of research. However, their cellular internalization remains a major limitation for the clinical application of oligonucleotides. To address this limitation, we report different strategies for the synthesis of specialized solid supports for the direct synthesis of 3′-oleyl-oligonucleotides by means of an l-threoninol derivative. A series of in vitro cell experiments were conducted to evaluate the potential of this strategy for enhanced cellular uptake. The results suggest that lipid conjugation enhances cellular uptake and facilitates oligonucleotide intracellular trafficking. Given these findings, the modification of therapeutic oligonucleotides through the attachment of lipidic moieties using a threoninol linker emerges as a valuable strategy to enhance their cellular internalization.
  Citation: Synlett ; : -
  PubDate: 2023-12-01T10:02:31+0100
  DOI: 10.1055/s-0042-1751528
anti-Selective Synthesis of Substituted β-Homoprolines by Rhodium Alkyl
Nitrene C–H Insertion
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  Authors: Tang; Xinxin, Noda, Hidetoshi, Shibasaki, Masakatsu
  Abstract: A range of β-homoprolines was prepared with high anti-selectivity. An intramolecular C–H insertion reaction involving a rhodium alkyl nitrene is a key step in the ring construction. The carboxylic acid in the products can serve as a springboard for further downstream transformations.
  Citation: Synlett ; : -
  PubDate: 2023-11-30T13:19:46+0100
  DOI: 10.1055/a-2201-7267
Enantioselective Sulfonation of Enones with Sulfinates by
Thiourea/Tertiary-Amine Catalysis
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  Authors: Wang; Si-fan, Yan, Ming, Shi, Jin-yi, Li, Guang-xun, Zhao, Jin-zhong
  Abstract: Chiral γ-keto sulfones are significant structures in both organic synthesis and pharmaceutical chemistry. Although there are many choices for obtaining racemic forms, only a few enantioselective methods have been reported. We have developed a simple way for obtaining chiral γ-keto sulfones in moderate yields and moderate enantiomeric ratios. Readily available sulfinates were directly used as substrates that could be converted into sulfinic acids by treatment with boric acid. The bifunctional catalyst forms a chiral ion pair with the sulfinic acid and controls the enantioselectivity of the sulfonation through hydrogen bonding.
  Citation: Synlett ; : -
  PubDate: 2023-11-30T12:47:24+0100
  DOI: 10.1055/a-2202-0842
Practical Fischer Indolization Using Bench-Stable Arylhydrazine Sulfonate
as the Surrogate of Arylhydrazine
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  Authors: Li; Wenjuan, Shen, Chaoren, Zhu, Yanping, Dong, Kaiwu
  Abstract: Fischer indolization using bench-stable sodium arylhydrazine sulfonate as a surrogate of arylhydrazine was developed. The preparation of arylhydrazine sulfonate was also modified by replacing sodium sulfite reductant with Pd-catalyzed hydrogen transfer. The straightforward synthesis of tetrahydrocarbazoles from the corresponding anilines was successfully conducted in a one-pot manner. A practical application of this method was demonstrated in the formal synthesis of pharmaceutical molecules Rizatriptan and Zolmitriptan.
  Citation: Synlett ; : -
  PubDate: 2023-11-30T12:27:40+0100
  DOI: 10.1055/s-0043-1763622
[4+1] Cyclizations to Enantiopure Multifunctional Cyclopentanes from
d-Glucose Using Formyl Dianion Synthons
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  Authors: Oelze; Silke, Bräuer, Nico, Michel, Tycho, Schaumann, Ernst, Kirschning, Andreas
  Abstract: The [4+1] cyclization of a sugar-based epoxytosylate with various C1 dianion equivalents provide highly functionalized homochiral cyclopentane derivatives. For these, a follow-up chemistry was developed to provide various cyclopentane building blocks as starting points for natural product syntheses. The [4+1] domino protocol relies on a 1,4-Brook rearrangement, which is essential for generating the second carbanion.
  Citation: Synlett ; : -
  PubDate: 2023-11-30T12:12:42+0100
  DOI: 10.1055/a-2201-3861
A Study on the Diazo-Transfer Reaction Using o-Nitrobenzenesulfonyl Azide
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  Authors: Gwak; Sungduk, Lee, Ji Hye, Kwon, Hyeok-Jun, Han, Hogyu
  Abstract: 15N-Labeled azides have a great potential as practical and effective tags for vibrational probing and hyperpolarized magnetic resonance imaging of biomolecules. They can be synthesized by reaction of primary amines with a 15N-labeled diazo-transfer reagent. TfNN15N, a γ-15N-labeled diazo-transfer reagent, was developed to prepare β-15N-labeled azides; these are vibrational probes devoid of strong spectral interference by Fermi resonance. To overcome the stability and safety problems associated with TfNN15N, there is a strong demand for the development of a novel γ-15N-labeled diazo-transfer reagent. We present a study on the diazo-transfer reaction using o-nitrobenzenesulfonyl azide (o-NsN3). o-NsNN15N, a γ-15N-labeled diazo-transfer reagent, was newly developed and found to be better than TfNN15N with respect to its physicochemical properties and ease of synthesis. Unlike TfNN15N, however, o-NsNN15N was found to afford a mixture of β- and γ-15N-labeled azides rather than the β-15N-labeled azide alone. A mechanism for the diazo-transfer reaction of o-NsNN15N with primary amines is proposed to explain the formation of such isotopomeric mixtures.
  Citation: Synlett ; : -
  PubDate: 2023-11-30T11:32:35+0100
  DOI: 10.1055/a-2184-4836
Remote Enantioselective Epoxidation Reactions Catalyzed by Chiral Iron
Porphyrin Complexes with a Hydrogen-Bonding Site
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  Authors: Ahmed; Hussayn, Pöthig, Alexander, Truong, Khai-Nghi, Bach, Thorsten
  Abstract: Iron porphyrin complexes, which were linked via a para-phenylethynyl group to a chiral scaffold with a lactam binding site, were probed as catalysts in the enantioselective epoxidation of 4-(ω-alkenyl)-quinolones. It was found that the 3-butenyl group in the substrate accounts for the highest enantioselectivity (up to 44% ee) and the absolute configuration of an oxirane product was elucidated by electron diffraction. A two-point hydrogen bond of the substrate to the catalyst is likely responsible for enantioface differentiation at a remote position. The study shows chirality transfer to be possible via four nonstereogenic carbon atoms between the binding site of the substrate and its reactive C=C double bond.
  Citation: Synlett ; : -
  PubDate: 2023-11-30T10:10:51+0100
  DOI: 10.1055/s-0042-1751527
Methods for the Synthesis of 1-Indanones Containing a β-Quaternary
Carbon Center
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  Authors: Song; Shuaishuai, Zhou, Wang
  Abstract: This article traces the development of synthetic routes toward 1-indanones containing a β-quaternary carbon center. The recent advancement in the regio- and chemoselective formal (4+1) carbocyclization of chalcones with internal alkynes via rhodium(III) catalysis for the synthesis of 1-indanones is highlighted.
  Citation: Synlett ; : -
  PubDate: 2023-11-30T09:41:25+0100
  DOI: 10.1055/s-0043-1763636
A Simplified Protocol for Large-Scale Preparation of 4CzIPN and 3DPA2FBN
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  Authors: Zhang; Yongda, Lei, Zhen, Xu, Yibo, Kosnik, Stephanie C., Jiang, Qi
  Abstract: Just in the past few years, the application of 4CzIPN as a photocatalyst in photochemistry has been dramatically increased with its unique properties. In the literature, a variety of protocols for the synthesis of 4CzIPN have been reported. However, a practical process for the preparation of 4CzIPN with consistent quality on large scale is not available, but highly desirable to enable the robust application of this photocatalysis in industry. Herein, we detailed a practical and simple column-free chemical process amenable for the large-scale production of 4CzIPN with high quality in 91% yield. Current process was demonstrated on large scale. The similar process protocol was applicable and demonstrated for the synthesis of 3DPA2FBN on large scale.
  Citation: Synlett ; : -
  PubDate: 2023-11-30T09:23:58+0100
  DOI: 10.1055/s-0042-1751523
Enzymatic Kinetic Resolution (EKR) of α-Allenols Enabled by a
Commercially Available Immobilized Lipase
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  Authors: Zhang; Tianyu, Zhu, Can
  Abstract: Enzymatic kinetic resolution (EKR) of racemates has been considered as an efficient and scalable technology to deliver enantiopure substances in an environmentally benign way. Herein, we develop a practical EKR of α-allenols enabled by a commercially available immobilized lipase, Lipozyme TL-IM. The stereoselectivity factor (S-factor) of this kinetic resolution (KR) was investigated to reach up to >1000. The robust nature of the EKR strategy is reflected by a broad scope of α-allenol substrates with the excellent control of enantioselectivity. This method offers an alternative approach to access chiral α-allenols, which can be easily transformed into many valuable oxycycles.
  Citation: Synlett ; : -
  PubDate: 2023-11-27T13:21:38+0100
  DOI: 10.1055/s-0042-1751525
Fluorescent 2′-Deoxyuridine (dU) Analogue: Tropolonyl triazolyl-dU
(tt-dU) Exhibits Solvatochromism/HeLa Cell Internalization and Its
Triphosphate (tt-dUTP) Is Incorporated into DNA Enzymatically
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  Authors: Meher; Sagarika, Gade, Chandrasekhar Reddy, Sharma, Nagendra K.
  Abstract: This era has witnessed the development and extensive application of modified nucleosides, including fluorescent nucleosides that clinically served humankind. Most fluorescent nucleoside analogues are derived from benzenoid aromatic scaffolds. However, the non-benzenoid aromatic moiety, tropolone, which exhibits unique hydrogen bonding and metal chelating properties, also occurs in nature. Recently, we introduced the tropolone unit at deoxyuridine through an ethyne linker and prepared its DNA analogues, which are fluorescent. This report describes the synthesis of a new troponyl triazolyl-dU (tt-dU) analogue, possessing a triazolyl linker, through click chemistry. tt-dU exhibits fluorescence with solvatochromism and enters into Hela cells without any cytotoxicity. Its triphosphate (tt-dUTP) was also synthesized and incorporated enzymatically into DNA, as shown in primer extension experiments. The unique photophysical properties and metal-chelating ability of the tropolone group make tt-dU a promising modified nucleoside.
  Citation: Synlett ; : -
  PubDate: 2023-11-27T12:41:51+0100
  DOI: 10.1055/a-2201-3756
Regioselective Double C–H Functionalization of Arenes via Aryl
Thianthrenium Salt Analogues
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  Authors: Hamad; Aboubakr, Mrozowicz, Michał, Xie, Yuanhao, Ritter, Tobias
  Abstract: Directed C–H functionalization reactions are powerful tools for the rapid and selective syntheses of complex molecules. However, many existing C–H functionalization reactions require the presence of a preinstalled directing group that has to be either a part of the molecule or introduced onto an existing functional group. Here, we report analogues of thianthrene that can also function as directing groups for intermediate directed C–H functionalization and thereby permit regioselective 2,4- and 3,4-aromatic C–H difunctionalization of simple arenes in yields of 22–33% over three steps.
  Citation: Synlett ; : -
  PubDate: 2023-11-27T12:07:29+0100
  DOI: 10.1055/s-0043-1763625
Ketone-Derived Pro-aromatic Reagents for Radical Group Transfer Reactions
and Deconstructive Functionalizations
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  Authors: Miñoza; Shinje, Librando, Ivy L., Liao, Hsuan-Hung
  Abstract: The recent prominence of ketones as handles for sp3-rich radicals has expanded the paradigm of synthetic utility of ketones, putting the ubiquitous functional group once again into the spotlight in recent years. One emerging strategy arose through ketone-derived pro-aromatic reagents in the form of dihydrobenzothiazoline (BTZ), dihydroquinazolinone (DHQZ), dihydropyrazole (DHP), and dihydro-1,2,4-triazole (DHT) as key intermediates for aromaticity-promoted C–C bond homolytic fission. The formed sp3-radicals could then participate in various radical functionalizations, including alkylations, arylations, olefination, alkynylation, silylations, amination, thiolation, and deuteration, among others, either in photocatalytic, thermal, or oxidative conditions. In this review, we highlight the implications and recent advances in using these pro-aromatic reagents in radical group transfer reactions and deconstructive functionalization.1 Introduction2 Aromatization-Driven C–C Bond Scission of Ketones3 Photochemical Reactions of Ketone-Derived Pro-aromatic Reagents4 Non-photochemical Reactions of Ketone-Derived Pro-aromatic Reagents5 Conclusion and Future Outlook
  Citation: Synlett ; : -
  PubDate: 2023-11-27T10:52:11+0100
  DOI: 10.1055/a-2197-1909
Photoredox-Catalyzed C(sp2)–H Bond Functionalization Reactions: A
Short Account
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  Authors: Li; Jinling, Zhao, Junjie, Loh, Teck-Peng
  Abstract: Photoredox catalysis has been undergoing rapid development and wide application in the chemical community during the past several years because of its advantages for reaction engineering. Since 2016, Loh et al. started their research on photoredox-catalyzed reaction transformations, including β-C(sp2)–H fluoroalkylation, alkylation, and acylation of enamides, C(sp2)–H phosphorylation of alkenes converted from alcohols, C(sp2)–H bromination, and alkylation of (hetero)arenes. These transformations introduce a broad range of structural differences on the C(sp2)–H bond of compounds with an extensive array of functional groups and showcase the appealing synthetic utilities of the approach.1 Introduction2 Photoredox-Catalyzed β-C(sp2)–H Functionalization of Enamides3 Photoredox-Catalyzed C(sp2)–H Functionalization of Alkenes4 Photoredox-Catalyzed C(sp2)–H Functionalization of (Hetero)Arenes5 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-11-27T09:36:24+0100
  DOI: 10.1055/a-2193-2682
Chiral Cyclodimerization Reactions: Construction of Nonnatural Dimeric
Carbazoles from (±)-4-Methylene-3-hydroxytetrahydrocarbazoles
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  Authors: Baire; Beeraiah, Mishra, Surabhi, Roy, Debayan
  Abstract: In this Synpacts article, we describe the concept of cyclodimerization in the biosynthesis and biomimetic synthesis of natural products and unnatural products. We also discuss key details of our discovery and development of a biomimetic-like, selective, homo- and heterochiral cyclodimerization strategy for the construction of nonnatural dimeric carbazole frameworks by employing a formal [3+2] annulation. Our work also demonstrated a novel reactivity of 1-(indol-2-yl)pent-4-yn-3-ols, and their potential as new synthetic building blocks in organic synthesis.1 Introduction: Chiral Cyclodimerization Reactions2 Biomimetic Syntheses of Natural Products through Chiral Cyclodimerizations3 Bioinspired Synthesis of Nonnatural Dimeric Carbazoles through Selective Chiral Cyclodimerizations4 Future Perspectives and Conclusions
  Citation: Synlett ; : -
  PubDate: 2023-11-27T08:50:23+0100
  DOI: 10.1055/a-2192-9235
Nickel-Catalyzed sp3 C–H Activation
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  Authors: Johnson; Colton E., Li, Shangyu, Arora, Ramon, Mirabi, Bijan, Lautens, Mark
  Abstract: Base metal catalyzed C–H activation represents a highly atom economic method to access functionalized molecules. This Account will focus on Ni-catalyzed C–H activation of sp3-hybridized carbon atoms with a particular focus on mechanism, recent applications, challenges, and outlook in this area. This Account will primarily focus on recent mechanistic work from 2017–2023.1 Base Metal C–H Activation2 Nickel-Catalyzed sp3 C–H activation3 Differences between Ni and Pd4 Mechanistic Considerations5 Elementary Steps6 Directed sp3 C–H Activation7 Choice of Directing Group8 Primary C–H Activation9 Secondary C–H Activation10 Tertiary C–H Activation11 Conclusion and Outlook
  Citation: Synlett ; : -
  PubDate: 2023-11-24T09:49:20+0100
  DOI: 10.1055/s-0042-1751519
Skeletal Rearrangements Involving Cyclopropyl- and Alkene-Stabilized
Silylium Ions
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  Authors: Long; Peng-Wei, He, Tao, Klare, Hendrik F. T., Oestreich, Martin
  Abstract: This Account summarizes the fascinating chemistry of cyclopropyl-stabilized silylium ions, which are readily available from vinylcyclopropanes (VCPs). Depending on the nucleophilic partner, these reactive intermediates undergo direct ring opening or ring expansion to nonclassical alkene-stabilized silylium ions. The latter can also be accessed by gold as well as proton electrophiles from silicon compounds containing unsaturated C–C bonds. All these reaction cascades can be terminated by C–H or C–C as well as Si–O bond formation. From this, a clearer picture of the versatility of these rather complex chemistries emerges.1 Introduction2 Skeletal Rearrangements of Vinylcyclopropanes Involving Cyclopropyl-Stabilized Silylium Ions2.1 Termination by C–H Bond Formation2.2 Termination by C–C Bond Formation3 Related Bond Reorganizations Involving Alkene-Stabilized Silylium Ions3.1 Initiation by Cationic Gold(I) Complexes3.2 Initiation by Brønsted Acids4 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-11-23T10:25:57+0100
  DOI: 10.1055/a-2188-1842
Microwave-Assisted Copper-Catalyzed Coupling of Bromoalkynes and
Sulfonamides: Rapid Synthesis of N-Sulfonyl Ynamides
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  Authors: Hong; Su Jeong, Lee, Joon-Ho, Yeom, Hyun-Suk
  Abstract: The synergistic effect of an alcohol solvent and microwave irradiation dramatically increased the C–N coupling rate, enabling the rapid synthesis of N-sulfonyl ynamides in ten minutes. The optimal catalyst, ligand, and solvent combination was investigated, and various bromoalkynes and sulfonamides were shown to be tolerated under these conditions.
  Citation: Synlett ; : -
  PubDate: 2023-11-22T10:34:59+0100
  DOI: 10.1055/a-2196-8886
Ring Transformation of Annulated Benzofuran Derivatives to Medium-Sized
Lactones
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  Authors: Fliegel; Lukas, Krauß, Julian, Christoffers, Jens
  Abstract: Benzannulated eight- and nine-membered-ring lactones were prepared by ring transformation of annulated benzofuran derivatives. The reaction sequence starts with a Brønsted acid catalyzed hydration of the enol ether moiety of the starting materials furnishing hemiacetals as intermediate products which underwent retro-Claisen-type C–C bond cleavage under the reaction conditions. The use of 15 mol% TfOH and two equivalents of water in CHCl3 at 85 °C turned out to be optimal. Products with exocyclic carboxylate function could be further derivatized by amide formation. In total, eleven medium-sized lactones were prepared. Furthermore, three benzannulated spirolactones were obtained from starting materials with exocyclic carboxamide moiety.
  Citation: Synlett ; : -
  PubDate: 2023-11-22T10:13:54+0100
  DOI: 10.1055/a-2192-4044
Asymmetric Cu(I)-Catalyzed Conjugate Borylation of
α,β-Unsaturated Acyl Silanes
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  Authors: Palermo; Anthony F., Imbriaco, Bianca, Chan, Samantha C., Doan, Brian A., Rousseaux, Sophie A. L.
  Abstract: We report the development of a Cu(I)-catalyzed conjugate borylation of α,β-unsaturated acyl silanes using bis(pinacoloto)diboron. Racemic borylations of β-aryl- and β-alkyl-substituted silyl enones were achieved using ligand-free conditions to access β-borylated acyl silanes in up to 97% yield. Josiphos enabled the synthesis of enantioenriched boronic esters in up to 58% yield and 94% ee. The racemic reaction was demonstrated on 5.0 mmol scale and isolation of the boronic esters was achieved using simple filtration and normal-phase chromatography. This work supplements known methods to access boronic esters from electron-deficient olefins using Cu(I) catalysis.
  Citation: Synlett ; : -
  PubDate: 2023-11-21T12:09:50+0100
  DOI: 10.1055/s-0043-1763621
Diastereoselective Access to anti-β-Hydroxy Sulfoxides from Chiral
Epoxides and Prochiral Sulfenate Anions: Mechanistic Insights, Scope,
and Limitation
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  Authors: Zhang; Jian, Betkekar, Vipul V., Suzuki, Keisuke, Ohmori, Ken
  Abstract: Reported herein is a stereoselective route to anti-β-hydroxy sulfoxides through the reaction of epoxides with sulfenate anions. Extensive experimental/computational studies revealed the dual special roles of MgBr2·OEt2, serving to generate the bromohydrin alkoxide intermediate, which undergoes nucleophilic attack on the prochiral sulfenate in a diastereoselective manner. The present study has opened a general stereoselective synthetic route to anti-β-hydroxy sulfoxides.
  Citation: Synlett ; : -
  PubDate: 2023-11-21T11:10:08+0100
  DOI: 10.1055/a-2196-5592
Synthesis of Alkyl Aryl Ethers by O-Arylation of Alcohols with
Diaryliodonium Salts: Scope, Limitations, and Mechanism
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  Authors: Gallagher; Rory T., Jha, Soocheta, Metze, Bryan E., Stuart, David R.
  Abstract: We describe the development of a C–O coupling reaction between aryl(2,4,6-trimethoxyphenyl)iodonium salts and aliphatic alcohols under weak base conditions. The scope of the reaction is presented, with 16 examples ranging in yield from moderate to high (54–96%). The limitations of the reaction are also presented. Mechanistic experiments reveal a complex network of reactions that include side reactions that generate arynes and oxidize the alcohol nucleophile.
  Citation: Synlett ; : -
  PubDate: 2023-11-21T10:56:38+0100
  DOI: 10.1055/a-2198-3637
Microwave-Assisted Functionalization of Single-Walled Carbon Nanotubes as
a Platform for a Supported Iridium Catalyst
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  Authors: Rodríguez-Flórez; Lesly V., Retamosa, María de Gracia, Martínez-Sánchez, Beatriz, Cazorla-Amorós, Diego, Nájera, Carmen, Yus, Miguel, Sansano, José M.
  Abstract: Single-walled carbon nanotubes (SWCNTs) were functionalized by treatment with imino esters through 1,3-dipolar cycloaddition activated by thermal 1,2-prototropy. The reaction was optimized and analyzed by using various heating methods. The functionalization afforded pyrrolidino-functionalized nanotubes that were characterized by using several techniques. The ester group was then transformed into the corresponding SWCNT–iridium carboxylate and, as a proof of concept, the product was tested as a catalyst in the hydrogen-transfer reaction of acetophenone to yield 1-phenylethanol.
  Citation: Synlett ; : -
  PubDate: 2023-11-20T12:46:14+0100
  DOI: 10.1055/a-2187-9368
Evaluation of a Bidentate ‘Clamp-Like’ Halogen-Bond Donor Motif Based
on Iodonium(III) Moieties
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  Authors: Reinhard; Dominik L., Kutzinski, Dana, Hatta, Masahito, Engelage, Elric, Huber, Stefan M.
  Abstract: A new motif for iodine(III)-based halogen-bond donors consisting of a 1,3-phenylene core and two cyclic five-membered diaryliodonium(III) wings was designed and its potential as a catalyst was evaluated. Its properties were analyzed in the solid state by X-ray crystallography and in solution by benchmark catalytic activation of a nitro-Michael addition between 5-methoxyindole and trans-β-nitrostyrene.
  Citation: Synlett ; : -
  PubDate: 2023-11-20T11:50:27+0100
  DOI: 10.1055/a-2198-3914
Polyconjugated Materials for Printed (Opto)Electronics: Introducing
Sustainability
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  Authors: Sassi; Mauro, Mattiello, Sara, Fappani, Alice, Beverina, Luca
  Abstract: This account summarizes the impact that the quest for sustainability is having on the field of organic polyconjugate molecules and polymers for plastic (opto)electronics. While at the proof-of-concept level, the design criteria as well as the preferred synthetic strategies to access new and improved materials have been dominated by the need for performance. The ongoing transition from the lab environment to the industrial scale imposes strict limitations on the cost and overall environmental impact of new materials. We here summarize our efforts on the development of new design criteria and synthetic strategies aimed at improving sustainability – without compromising performance – in organic polyconjugated molecules. The article is composed of three sections: Introduction and motivation, sustainability through improved synthetic methods and through improved design.Outline1 Introduction and Motivation2 Sustainable Reaction Methods2.1 The New Tools: Reactions in Aqueous Solution of Surfactants2.2 Intrinsically More Sustainable Reactions: Direct Arylation2.3 Sustainable Multistep Protocols: Combining Micellar, Solventless, and Mechanochemical Methods3 Sustainability as a Design Criterion: De Novo Design4 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-11-20T09:47:40+0100
  DOI: 10.1055/a-2191-6011
Efficient Protosilylation of Unsaturated Compounds with Silylboronates
over a Heterogeneous Cu3N Nanocube Catalyst
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  Authors: Xu; Hang, Yamaguchi, Sho, Mitsudome, Takato, Mizugaki, Tomoo
  Abstract: Copper-catalyzed protosilylation of unsaturated compounds with silylboronates has attracted attention for the production of organosilanes; however, the use of organic ligands or bases is unavoidable. Herein, we report a heterogeneous catalytic system for the protosilylation of unsaturated compounds with silylboronates under mild and additive-free conditions over copper nitride nanocubes (Cu3N NCs). This method can be applied to various substrates (e.g., alkynes, alkenes, or imines) to afford the corresponding organosilicon compounds. The Cu3N NC catalyst can be easily recovered and reused several times. Thus, the active and reusable Cu3N NC catalyst offers a green and sustainable method for efficient organosilane production.
  Citation: Synlett ; : -
  PubDate: 2023-11-17T12:18:15+0100
  DOI: 10.1055/a-2191-5906
Stereocontrolled Aldol-Like Reactions Involving Oxocarbenium Intermediates
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  Authors: Galeote; Oriol, Kennington, Stuart C. D., Mellado-Hidalgo, Miguel, Costa, Anna M., Romea, Pedro, Urpí, Fèlix
  Abstract: Oxocarbenium cations are key intermediates for the stereocontrolled construction of carbon–carbon bonds. In particular, we have developed a wide range of stereoselective aldol-like processes that take advantage of the high reactivity of the oxocarbenium species arising from acetals, glycals, and orthoesters with metal enolates. This Account describes the development and optimization of such processes, together with other significant contributions, with a particular emphasis on their application to the synthesis of natural products.1 Introduction2 Substrate-Controlled Processes2.1 Additions to Acyclic Acetals2.2 Additions to Cyclic Acetals3 Chiral-Auxiliary-Based Processes3.1 Additions to Acyclic Acetals3.2 Additions to Cyclic Acetals and Glycals4 Chiral-Catalysis-Based Processes4.1 Organocatalysis4.2 Metal Catalysis5 Conclusions
  Citation: Synlett ; : -
  PubDate: 2023-11-17T11:01:39+0100
  DOI: 10.1055/a-2184-5115
Synthesis of 2-Aminopyridine-Modified Peptide Nucleic Acids
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  Authors: Kumpina; Ilze, Baskevics, Vladislavs, Walby, Grant D., Tessier, Brandon R., Saei, Sara Farshineh, Ryan, Christopher A., MacKay, James A., Katkevics, Martins, Rozners, Eriks
  Abstract: Triplex-forming peptide nucleic acids (PNAs) require chemical modifications for efficient sequence-specific recognition of DNA and RNA at physiological pH. Our research groups have developed 2-aminopyridine (M) as an effective mimic of protonated cytosine in C+•G-C triplets. M-modified PNAs have a high binding affinity and sequence specificity as well as promising biological properties for improving PNA applications. This communication reports the optimization of synthetic procedures that give PNA M monomer in seven steps, with minimal need for column chromatography and in good yields and high purity. The optimized route uses inexpensive reagents and easily performed reactions, which will be useful for the broad community of nucleic acid chemists. Thought has also been given to the potential for future development of industrial syntheses of M monomers.
  Citation: Synlett ; : -
  PubDate: 2023-11-17T10:13:25+0100
  DOI: 10.1055/a-2191-5774
Nickel-Catalyzed Hydroalkynylation of 1,3-Dienes with Simple Alkynes
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  Authors: Yao; Bo-Ying, Xiao, Wei-Guo, Xiao, Li-Jun, Zhou, Qi-Lin
  Abstract: A hydroalkynylation reaction of 1,3-dienes with simple alkynes, facilitated by an efficient nickel catalyst system with the 9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene (Xantphos) ligand, is presented. This reaction displays a broad substrate range for alkynes, encompassing both aryl alkynes and alkyl alkynes, thereby overcoming previous constraints in 1,3-diene hydroalkynylation. The method offers a convenient and direct means for obtaining allylic alkynes with high atom and step economy.
  Citation: Synlett ; : -
  PubDate: 2023-11-16T13:10:04+0100
  DOI: 10.1055/s-0043-1763605
Copper-Catalyzed Regiodivergent Borylation of Fluorinated Alkynes and
Palladium-Catalyzed Regiospecific Suzuki–Miyaura Cross-Coupling
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  Authors: Rummler; Lénaic, Sater, Mariam Abd El, Blanchard, Nicolas, Bizet, Vincent
  Abstract: Alkenylboranes are key intermediates in modern organic synthesis, and they are usually obtained by the borylation of alkynes. We report herein highly regio- and stereoselective syntheses of α,Z- and β,Z-trifluoromethylated alkenylboranes by copper-catalyzed borylation reactions. Further functionalizations by palladium-catalyzed Suzuki–Miyaura cross-couplings have been developed and, interestingly, a marked difference in reactivity between the α- and β-borylated isomers has been identified.
  Citation: Synlett ; : -
  PubDate: 2023-11-16T12:42:11+0100
  DOI: 10.1055/a-2192-6996
Bismuth-Centered Radical Species: Access and Applications in Organic
Synthesis
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  Authors: Martínez; Sebastián, Lichtenberg, Crispin
  Abstract: Recent advances in the isolation of tamed bismuth radicals and the selective in situ generation of highly reactive bismuth radicals have set the stage for the application of these compounds in organic and organometallic synthesis and catalysis. Here, we provide a summary of the methodological approaches in the field. Important strategies for accessing bismuth radical species are presented and key examples of their applications in organic synthesis are outlined, highlighting how this class of compounds has emerged as new set of valuable tools for synthetic practitioners.1 Introduction2 Generation of Bismuth Radical Species by Homolysis2.1 Temperature-Induced Homolysis2.2 Light-Induced Homolysis2.3 Light-/Temperature-Induced Bi–C Homolysis of Polar Oxidative Addition Complexes3 Applications of Bismuth-Centered Radical Species in Organic Synthesis3.1 Bismuth-Catalyzed Cycloisomerization of Iodo Olefins3.2 Controlled Radical Polymerization Reactions3.3 Bismuth-Promoted Pn–Pn and C–S Coupling3.4 Bismuth-Catalyzed Dehydrocoupling of Silanes with TEMPO3.5 Bismuth-Catalyzed C–N Coupling with Redox-Active Electrophiles3.6 Bismuth-Catalyzed Giese-Type Coupling Reactions3.7 Oxidative Addition of Aryl Electrophiles to Photoactive Bismuthinidenes4 Conclusions
  Citation: Synlett ; : -
  PubDate: 2023-11-16T12:20:42+0100
  DOI: 10.1055/a-2187-0455
Purine-Based AIEgens with Different Morpholine Substitution Sites and
Their Application in Lipophagy Imaging
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  Authors: Shi; Lei, Yu, Ai-Wen, Meng, Wei-Han, Xie, Kun-Peng, Li, Kun
  Abstract: Lysosomes are an important organelle involved in many physiological processes. However, enhancing the accurate localization of lysosomes by chemical modification is still a problem. Herein, the purine-based AIEgens with different morpholine substitution sites were constructed. The effects of modification sites on the absorption, fluorescence, pH, viscosity and bioimaging properties of the probes were systematically studied. The morpholine modification at the phenyl site could effectively enhance the fluorescence behavior and the lysosome specificity. The morpholine-modified AIEgens could achieve the further lysosome imaging during the lipophagy process. This basic study might do favor to design more probes for further lysosome function studies.
  Citation: Synlett ; : -
  PubDate: 2023-11-15T10:23:58+0100
  DOI: 10.1055/a-2201-3612
Synergistic Organoboron/Palladium Catalysis for Regioselective
N-Allylation of 2-Pyridones, 4-Pyridones, and Related Ambident
Heterocycles
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  Authors: Yatzoglou; Giorgos, Zambri, Matthew T., Desai, Shrey P., Taylor, Mark S.
  Abstract: The use of a boronic acid co-catalyst along with a palladium complex enables efficient dehydrative couplings of allylic alcohols and tautomerizable heterocycles. The protocol has been applied to achieve N-allylations of 2-pyridones, 4-pyridones, 4-pyrimidinones, and their benzofused derivatives.
  Citation: Synlett ; : -
  PubDate: 2023-11-15T09:43:44+0100
  DOI: 10.1055/s-0043-1763618
Synthesis of Symmetrical Disulfides by an NIS/PPh3-Mediated Reductive
Self-Coupling of Sulfonyl Hydrazides
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  Authors: Yadav; Ashvani, Gond, Amrit, Prasad, Virendra
  Abstract: The present study discloses an NIS/PPh3-mediated reductive self-coupling of arylsulfonyl hydrazides to prepare symmetric diaryl disulfides. This methodology has a broad functional-group tolerance and a high scalability. This strategy permits the introduction of sulfonyl hydrazides into the synthesis of symmetrical organic disulfides without the use of a catalyst or base, and symmetrical aromatic disulfides can be prepared in moderate to excellent isolated yields from inexpensive and readily available starting materials.
  Citation: Synlett ; : -
  PubDate: 2023-11-10T12:30:57+0100
  DOI: 10.1055/s-0041-1738457
Facile Installation of β-Hydroxyarylethylamino Motifs at the C2-Position
of Quinoline Moiety via Copper-Catalyzed [3+3]-Cycloaddition Reaction of
N-Oxide with N-Ts Aziridine
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  Authors: Konwar; Monuranjan, Das, Tapashi, Naskar, Arpan, Murmu, Ranjit, Das, Animesh
  Abstract: A general and atom-efficient synthesis of quinoline-C2-substituted β-hydroxyarylethylamino derivatives was achieved by copper-catalyzed [3+3]-cycloaddition reaction of N-oxide with N-Ts aziridines. Notably, temperature has a huge impact on this transformation as evidenced by the fact that, at 80 °C, exclusively the [3+3] cycloadduct was isolated whereas, at elevated temperature (140 °C), it has been converted into the aminated product with good yield. Notably, there is no byproduct in the overall process. The use of base-free conditions, excellent site selectivity, and good functional group tolerance are the important features of the process.
  Citation: Synlett ; : -
  PubDate: 2023-11-10T12:12:02+0100
  DOI: 10.1055/a-2184-4940
Dearomatization of α-Unsubstituted β-Naphthols
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  Authors: Li; Ying, Feng, Kongling, Zhao, Ruinan, Zhu, Cuiju, Xu, Hao
  Abstract: This Account summarizes the highly appealing dearomatization reactions of β-naphthols for the synthesis of highly functionalized, three-dimensional structures starting with simple planar aromatic compounds. The reactions are categorized mainly from the viewpoint of the construction of carbon–hydrogen, carbon–carbon, and carbon–hetero bonds (C–N/O, C–Cl, C–F) at the α-position of β-naphthols. The dearomatized products play an important role in organic synthesis and materials science.1 Introduction2 Construction of Carbon–Hydrogen Bonds at the α-Position of β-Naphthols3 Construction of Carbon–Carbon Bonds at the α-Position of β-Naphthols4 Construction of Carbon–Nitrogen/Oxygen Double Bond at the α-Position of β-Naphthols5 Construction of Carbon–Carbon and Carbon–Oxygen Bonds at the α-Position of β-Naphthols6 Construction of Carbon–Halogen Bonds at the α-Position of β-Naphthols7 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-11-10T08:12:08+0100
  DOI: 10.1055/s-0042-1751520
Practical Site-Selective Oxidation of Glycosides with Palladium(II)
Acetate/Neocuproine
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  Authors: Reintjens; Niels R. M., Bartels, Imke M. A., Marinus, Nittert, Massmann, Sarina C., Bunt, Daan V., Walvoort, Marthe T. C., Witte, Martin D., Minnaard, Adriaan J.
  Abstract: The palladium-catalyzed oxidation of the secondary C(3) hydroxy group of glycopyranosides has set a mark in the selective modification of unprotected carbohydrates. The preformed catalyst [(neocuproine)PdOAc]2(OTf)2 oxidizes di- and oligosaccharides, as well as monosaccharides. Here, we provide a more convenient protocol for this reaction in which the Pd catalyst is formed in situ from Pd(OAc)2 and neocuproine in methanol at 50 °C. Together with a simplified product isolation, this protocol was applied to a series of mono- and disaccharides, and has been applied on a 10 gram scale. The protocol is also valuable as a screening method to determine whether more-extensive studies using the preformed catalyst are worthwhile.
  Citation: Synlett ; : -
  PubDate: 2023-11-09T12:04:32+0100
  DOI: 10.1055/a-2186-1485
Retrosynthetic Simplicity
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  Authors: Levin; Mark D.
  Abstract: Retrosynthetic simplicity is introduced as a metric by which methods can be evaluated. An argument in favor of reactions which are retrosynthetically simple is put forward, and recent examples in the context of skeletal editing from my own laboratory as well as contributions from others are analyzed critically through this lens.1 Introduction2 Example 1: Quinoline to Quinazoline (One Product, Two Starting Materials)3 Example 2: Benzene to Pyridine (Two Products, One Starting Material)4 Caveats, Counterarguments, and Conclusions
  Citation: Synlett ; : -
  PubDate: 2023-11-09T11:27:04+0100
  DOI: 10.1055/s-0043-1763623
Molybdenum-Catalyzed Directed Activation of Aryl Chlorides and Fluorides
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  Authors: Banerjee; Somsuvra, Matsushita, Naoki, Nakamura, Eiichi, Patil, Nitin T., Asako, Sobi, Ilies, Laurean
  Abstract: A low-valent molybdenum species generated by the reduction of a molybdenum precursor with phenylmagnesium bromide catalytically cleaves a C–Cl or C–F bond in an aromatic ketone under mild conditions, followed by cyclization to produce a hydroxyphthalan (1,3-dihydro-2-benzofuran-1-ol) derivative.
  Citation: Synlett ; : -
  PubDate: 2023-11-06T12:29:14+0100
  DOI: 10.1055/a-2187-9441
Synthesis of 2,4-Disubstituted Oxazoles by a Copper-Catalyzed [3+2]
Annulation/Olefination Cascade between Amides and IIII/PV Hybrid Ylides
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  Authors: Ye; Xingchen, Wang, Zhaofeng
  Abstract: We report a novel and efficient method for oxazole synthesis through a copper-catalyzed [3+2] annulation/olefination cascade between readily available iodonium–phosphonium hybrid ylides and amides. An unprecedented α-phosphonium Cu carbenoid acts as the key intermediate. This method features excellent regioselectivity with mild reaction conditions and a broad substrate scope. Its synthetic utility is demonstrated by its application in late-stage functionalizations and the rapid synthesis of a chiral ligand based on an oxazole motif.
  Citation: Synlett ; : -
  PubDate: 2023-11-06T09:03:29+0100
  DOI: 10.1055/a-2185-0673
Chromium-Promoted Dearomative (Deutero)Hydrocyanoalkylation of
(Hetero)Arenes Using Simple Alkylnitriles
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  Authors: Zeng; Wei-Long, Jiang, Xu, Li, Wei
  Abstract: Herein, a general strategy for the regioselective dearomative 1,2-hydrocyanoalkylation of chromium-bound (hetero)arenes with simple alkylnitriles as pronucleophiles was disclosed, providing rapid access to 1,3-cyclohexadienes possessing useful alkylnitrile groups. The versatility of this methodology further enabled a selective dearomative deuteration reaction. Finally, synthetic applications of the method in the formal synthesis of natural products, including erysotramidine, demethoxyerythratidinone, and morphine, were demonstrated.
  Citation: Synlett ; : -
  PubDate: 2023-11-06T09:03:25+0100
  DOI: 10.1055/a-2185-0581
Visible-Light-Mediated Intramolecular Lactonization of Benzylic C(sp3)–H
Bonds Promoted by DDQ and tert-Butyl Nitrite
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  Authors: Hu; Miaomiao, Yang, Jiangyu, Niu, Mengyu, Li, Chunmei, Xu, Meng, Li, Meichao, Shen, Zhenlu
  Abstract: A functionalization of benzylic C(sp3)–H bonds was established through a mild metal-free intramolecular lactonization protocol in the presence of DDQ/tert-butyl nitrite as photocatalysts, allowing practical and low-cost access to a series of phthalide products in moderate to excellent yields. Compared with many existing methodologies, this visible-light-driven process exhibits an excellent substrate scope and fascinating features, including the formation of water as the sole byproduct, an abundant and green energy source, commercially available catalysts, and room-temperature reaction. Finally, detailed mechanistic investigations clearly revealed the role of the photocatalysts and molecular oxygen.
  Citation: Synlett ; : -
  PubDate: 2023-11-03T12:25:55+0100
  DOI: 10.1055/a-2185-4286
Photoinduced Metal-Free Arylboration of Unactivated Alkenes: Synthesis of
Indoline Boronic Ester
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  Authors: Lu; Ji, He, Yangsen, Ren, Lixu, Li, Daling, Pan, Xianchao, Yang, Lin, Wang, Jun, Wei, Siping, Wei, Jun
  Abstract: The environmentally benign synthesis of indoline boronic esters, especially through a way of arylboration to alkenes, remains a challenge due to the use of transition metals or high-temperature conditions. We described a photoinduced metal-free arylboration of unactivated alkenes for the synthesis of indoline boronic esters and 1,2,3,4-tetrahydroquinoline boronic ester in good yields. This approach showed good compatibility and great efficiency for a range of allylphenylamines as well as alkylamine. Remarkably, this transformation also suggested that the base is not necessary for photosensitizer-free diboron reagent mediated mild generation of aryl radical. Furthermore, compared to previously reported methods, this approach is mild and environmentally benign.
  Citation: Synlett ; : -
  PubDate: 2023-11-03T12:25:49+0100
  DOI: 10.1055/a-2184-5014
Diastereoselective Cross-Dehydrogenative Coupling Reactions of Amides with
Diarylmethanes Using DDQ through Oxidative C–H Benzylic Activation
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  Authors: Kimura; Nagisa, Nakata, Kenya
  Abstract: This study reports the chiral-auxiliary-controlled diastereoselective dehydrogenative coupling of diarylmethanes with amides by using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone as the oxidant. The scope of the proposed reaction is very broad, with a wide variety of substrates and nucleophiles being applicable. The chiral induction can be attributed to the coordination of the oxygen atom on the chiral auxiliary with the carbocation intermediates.
  Citation: Synlett ; : -
  PubDate: 2023-11-02T12:14:42+0100
  DOI: 10.1055/a-2182-7532
Total Synthesis of Marine Macrolide Natural Products by the
Macrocyclization/Transannular Pyran Cyclization Strategy
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  Authors: Fuwa; Haruhiko
  Abstract: In this Account, we summarize the development of a new strategy for streamlined synthesis of tetrahydropyran-embedded macrolactones and its successful implementation to a 13-step synthesis of (–)-exiguolide and an 11-step synthesis of (+)-neopeltolide.1 Introduction2 Development of Macrocyclization/Transannular Pyran Cyclization Strategy3 Total Synthesis of (–)-Exiguolide4 Total Synthesis of (+)-Neopeltolide5 Conclusions
  Citation: Synlett ; : -
  PubDate: 2023-11-02T11:53:24+0100
  DOI: 10.1055/a-2181-9876
Total Synthesis of Mavacuran Alkaloids via Bioinspired and Non-Bioinspired
Strategies
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  Authors: Kouklovsky; Cyrille, Poupon, Erwan, Evanno, Laurent, Vincent, Guillaume
  Abstract: In this account, we report our endeavors towards the total synthesis of the mavacuran alkaloids and some of their highly natural complex bis-indoles. Our studies started with the hemisynthesis of voacalgine A and bipleiophylline, made an excursion to a related family of monoterpene indole alkaloids (total synthesis of 17-nor-excelsinidine) and ended with the total syntheses of several mavacuran alkaloids (16-epi-pleiocarpamine, 16-hydroxymethylpleiocarpamine, taberdivarine H, normavacurine, C-mavacurine, C-profluorocurine, and C-fluorocurine) via a combination of bioinspired and non-bioinspired synthetic routes.1 Introduction2 Bioinspired Hemisynthesis of Voacalgine A and Bipleiophylline3 Total Synthesis of the Mavacuran Alkaloids4 Bioinspired Oxidative Cyclization of a Geissoschizine Ammonium Derivative to Form the N1–C16 Bond and the E Ring5 Non-Bioinspired Michael Addition to Form the C15–C20 Bond and the E Ring6 Conclusion7 Epilogue
  Citation: Synlett ; : -
  PubDate: 2023-11-02T08:51:09+0100
  DOI: 10.1055/s-0042-1751498
Iridium-Catalyzed Ligand-Controlled Semi-Reduction of Alkynes Employing
H2O as the Hydrogen Donor and Its Application
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  Authors: Zhao; Wei, Zhou, Siyi, Wang, Chengniu, Zhang, Yi, Xu, Dawei
  Abstract: An iridium-catalyzed ligand-controlled semi-reduction of alkynes employing H2O as the hydrogen donor, together with its application, is reported. The use of di-tert-butylphosphinous chloride is crucial for stereoselectivity toward Z-olefins, whereas the use of 2-(diphenylphosphino)benzaldehyde is crucial for stereoselectivity toward E-olefins. More than 35 alkenes were obtained in good yields and high stereoselectivities. The utility of the current method in practical applications was investigated by studying the drug effects of (E)-1,3-dimethoxy-5-styrylbenzene on nerve growth in a zebrafish model.
  Citation: Synlett ; : -
  PubDate: 2023-11-02T08:25:31+0100
  DOI: 10.1055/s-0042-1751516
A Golden Synthetic Approach to 2-(1H-Pyrrol-1-yl)anilines and
Pyrrolo[1,2-a]quinoxalines through a Gold Carbene Intermediate
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  Authors: Tasdemir; Volkan, Genç, Hasan, Menges, Nurettin
  Abstract: The pyrrolo[1,2-a]quinoxaline skeleton has significant potential for many biological and optical applications. Hence, in this study, unconjugated ynone derivatives were treated with 1,2-diaminoarenes in a gold-catalyzed cyclization to give 2-(1H-pyrrol-1-yl)anilines, which are valuable starting materials, and pyrrolo[1,2-a]quinoxalines by a one-pot and single-step approach. A reaction mechanism for the formation of the pyrrolo[1,2-a]quinoxaline skeleton featuring a key gold carbene intermediate is proposed. On the other hand, the methyl group on the C-2 position of the 2-(1H-pyrrol-1-yl)anilines was oxidized by SeO2 to give the pyrrolo[1,2-a]quinoxaline skeleton, resulting in 14 different pyrrolo[1,2-a]quinoxaline derivatives.
  Citation: Synlett ; : -
  PubDate: 2023-10-31T11:27:58+0100
  DOI: 10.1055/a-2159-9400
Construction of Bibenzothiophenes through Oxidative C–H Cyclization
with 1,3-Diynes
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  Authors: Chen; Jingyi, Lei, Tao, Wan, Danyang, Yang, Yudong
  Abstract: The development of concise and efficient methods to construct bithiophene derivatives is an appealing task in the fields of organic chemistry and organic functional materials. Herein, we summarize our recent efforts towards the development of catalytic oxidative C–H cyclization reactions of thiophenol derivatives with 1,3-diynes, which provides a straightforward and effective synthetic approach to both symmetrical and nonsymmetrical 3,3′-bibenzothiophenes. This work is expected to stimulate the application of catalytic oxidative C–H annulation of aromatics with 1,3-diynes for the exploitation of organic functional materials.
  Citation: Synlett ; : -
  PubDate: 2023-10-31T09:51:36+0100
  DOI: 10.1055/s-0042-1751514
Rose Bengal Promoted Catalytic Amyloid-β Oxygenation by
Sonoactivation
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  Authors: Atsumi; Wataru, Kawabata, Keiichi, Yamane, Mina, Oi, Miku, Mitsunuma, Harunobu, Sohma, Youhei, Hori, Yukiko, Tomita, Taisuke, Kanai, Motomu
  Abstract: Catalytic photooxygenation of amyloid-β is a leading therapeutic strategy for the treatment of Alzheimer disease; however, the limited tissue permeability of light hampers its clinical application. We here report an alternative catalytic sonooxygenation strategy to circumvent this problem. Amyloid-β aggregates were oxygenated by using rose bengal as a sonosensitizer under ultrasound irradiation. Structure–activity relationships revealed that xanthene-derived catalysts containing halogen atoms furnished a superior amyloid oxygenation activity.
  Citation: Synlett ; : -
  PubDate: 2023-10-30T13:04:40+0100
  DOI: 10.1055/a-2182-7614
Reaction of Highly Volatile Organic Compounds with Organolithium Species
in Flow Microreactor
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  Authors: Muta; Kensuke, Okamoto, Kazuhiro, Nagaki, Aiichiro
  Abstract: Highly volatile organic compounds (VOCs) with boiling points (bp) around or below room temperature are generally difficult to manipulate precisely in liquid-phase organic reactions although they offer significant atom-economic advantages. We have developed a novel approach using a jacketed syringe pump to enable the formylation of organolithium species in a continuous-flow system under ambient pressure. Methyl formate (bp 32 °C) worked as a formylating agent and was successfully delivered to the continuous operation for over 30 minutes in our microflow system. This methodology was successfully expanded to the application of acetaldehyde (bp 21 °C) and heptafluoropropyl bromide (bp 12 °C).
  Citation: Synlett ; : -
  PubDate: 2023-10-30T12:40:21+0100
  DOI: 10.1055/a-2170-2976
Pd-catalyzed Stereodivergent [4+2] Annulation to Access [6.7]-Fused
N-Heterocycles
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  Authors: Ma; Zhan-Cai, Huang, Yuan
  Abstract: Stereodivergent synthesis of N-heterocycle frameworks bearing 1,3-nonadjacent stereogenic centers through a single transformation remains a high-priority challenge in organic synthesis. Herein, we highlight our recent discovery of stereodivergent access to such useful structural motifs using Pd-catalyzed [4+2] annulation reactions of vinyl benzoxazinaones and seven-membered cyclic N-sulfonyl aldimines. A wide range of N-heterocycles with 1,3-nonadjacent stereogenic centers were obtained in high efficiency and stereodivergency. Importantly, the polarity of solvents was found to play a key role in switching the diastereoselectivity. Furthermore, good enantioselectivities of these reactions were achieved by the employment of commercially available Wingphos as the chiral ligand.
  Citation: Synlett ; : -
  PubDate: 2023-10-30T11:59:46+0100
  DOI: 10.1055/a-2184-6373
Ruthenium(II)-Catalyzed Selective C–H Bond Activation of Biindoles and
Coupling with Sulfoxonium: An Efficient Access to
Pyrido[1,2-a:4,3-b′]diindole frameworks
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  Authors: Jatoth; Ramanna, Gugulothu, Kishan, Valappil, Rasika Meloth, Nelson, Nithya, Kumar, K. Shiva
  Abstract: A ruthenium-catalyzed selective C–H functionalization/annulation cascade reaction of biindoles and sulfoxonium ylides has been developed. The reaction selectively provides pyrido[1,2-a:4,3-b′]diindole (5H-benzo[2,3]indolizino[7,8-b]indole) derivatives in good yields. A possible mechanism for the reaction pathway is proposed. More importantly, the present study provides a useful method for the construction of pyrido[1,2-a:4,3-b′]diindole frameworks.
  Citation: Synlett ; : -
  PubDate: 2023-10-30T11:40:31+0100
  DOI: 10.1055/a-2179-6438
Assembling Nitroamino and Amino Groups on a Pyrazolyl-1,3,4-Oxadiazole
Framework for the Construction of High-Performance and Insensitive
Energetic Materials
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  Authors: Zeng; Zhiwei, Zhao, Zichang, Yin, Zhaoyang, Tang, Mingjie, Liu, Yuji, Huang, Wei, Tang, Yongxing
  Abstract: The introduction of nitroamino groups onto a nitrogen-rich heterocyclic skeleton is an efficient method for constructing high-performance energetic compounds. In this work, the nitroamino-functionalized compound 4-(5-amino-1,3,4-oxadiazol-2-yl)-N,N′-dinitro-1H-pyrazole-3,5-diamine was synthesized in yields of up to 83%. In addition, its energetic salts were also prepared. All these compounds were characterized by NMR and IR spectroscopy and, in two cases, by single-crystal X-ray diffraction. In addition, the difference in the reactivities of the three amino groups on the pyrazolyloxadiazole system was analyzed by an average local ionization energy analysis. The hydrazinium salt of the diamine exhibits promising detonation properties and good molecular stability, suggesting it has good application potential. Compared with previous works, this strategy gives an improved isolated yield and provides a promising method for the construction of nitroamino-functionalized 1,3,4-oxadiazole derivatives.
  Citation: Synlett ; : -
  PubDate: 2023-10-30T09:28:13+0100
  DOI: 10.1055/a-2181-0453
Catalytic C–H Functionalization of Trimethylamine
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  Authors: Geik; Dennis, Büker, Alina, Fornfeist, Felix, Schmidtmann, Marc, Doye, Sven
  Abstract: Carbon–carbon bond-forming hydroaminoalkylation reactions between trimethylamine and alkynes, alkenes, allenes, or a methylenecyclopropane (MCP) are achieved in the presence of titanium catalysts. The reactions take place by C–H bond activation at the methyl group of trimethylamine and therefore offer flexible and direct methods for the C–H functionalization of trimethylamine. The importance of the developed procedures for the synthesis of pharmaceutically relevant dimethylaminomethyl-substituted products is underlined by a straightforward synthesis of the antidepressant butriptyline.
  Citation: Synlett ; : -
  PubDate: 2023-10-30T09:09:26+0100
  DOI: 10.1055/a-2179-6032
Regioselective Ring Opening of Oxetanes Enabled by Zirconocene and
Photoredox Catalysis
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  Authors: Aida; Kazuhiro, Ota, Eisuke, Yamaguchi, Junichiro
  Abstract: Oxetanes are frequently utilized in organic synthesis, both as target products and as fairly reactive intermediates. Whereas ring cleavage of oxetanes through polar mechanisms has been extensively investigated, their radical-based counterparts remain underexplored. We used zirconocene and photoredox catalysis to open an oxetane ring in a radical manner. In our protocol, the reaction selectively delivers the more-substituted alcohols via putative less-stable radicals. This method not only affords the corresponding hydrogenated products, but also provides unique benzylidene acetal products.
  Citation: Synlett ; : -
  PubDate: 2023-10-27T12:19:17+01:00
  DOI: 10.1055/s-0041-1738454
Thermostable Insensitive Energetic Materials Based on a Triazolopyridine
Fused Framework with Alternating Nitro and Amine Groups
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  Authors: Ran; You, Xia, Honglei, Song, Siwei, Wang, Kangcai, Zhang, Qinghua
  Abstract: In this work, we designed and synthesized a series of novel triazolopyridine fused-ring compounds with alternating nitro and amine groups. Three compounds showed remarkable thermal stability at 256, 310, and 294 °C, respectively, and a low mechanical sensitivity [impact sensitivity (IS) = 40 J, friction sensitivity (FS) = 324 N; IS = 35 J, FS = 240 N; and IS > 40 J, FS = 324 N, respectively]. Significantly, two of these compounds exhibited a better detonation performance [detonation velocity (D) = 8200 and 8335 m s–1, Detonation pressure (P) = 25.6 and 27.2 GPa, respectively] than the widely used heat-resistant explosive hexanitrostilbene (HNS; D = 7612 m s–1, P = 24.3 GPa). Additionally, a nitramine derivative displayed a detonation performance (D = 8569 m s–1, P = 31.3 GPa) similar to that of the high-energy explosive RDX. The superior properties of the materials were further confirmed by X-ray diffraction analysis and by several theoretical calculations (ESP, LOL–π, Hirshfeld surfaces, RDG, and NCI analyses). These results indicated that the three compounds might be potential candidates for use as heat-resistant energetic materials.
  Citation: Synlett ; : -
  PubDate: 2023-10-27T12:19:13+01:00
  DOI: 10.1055/s-0043-1763570
Electrocatalytic Synthesis of 1,2-Dioxolanes from Tetrasubstituted
Donor–Acceptor Cyclopropanes
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  Authors: Oliver; Gwyndaf A., Kolb, Simon, Werz, Daniel B.
  Abstract: An electrochemical method for the synthesis of 3,3,5,5-tetrasubstituted 1,2-dioxolanes from donor–acceptor cyclopropanes with quaternary donor positions is described. This catalyst-free strategy delivers radical cations after C(sp3)–C(sp3) cleavage by direct anodic oxidation of the strained carbocycle. A broad scope with regard to the cyclopropanes employed in the reaction is presented. Additionally, we propose a plausible mechanism for the reaction.
  Citation: Synlett ; : -
  PubDate: 2023-10-25T08:29:38+01:00
  DOI: 10.1055/a-2179-6320
[Pyridine–SO3H]ZnCl3: A Multipurpose Catalyst for A3 Coupling Synthesis
of Propargylamines under Mild Conditions
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  Authors: Moosavi-Zare; Ahmad Reza, Rezaei-Gohar, Mohammad, Tavasoli, Mahsa, Goudarziafshar, Hamid
  Abstract: N-Sulfopyridin-1-ium monozinc(II) trichloride ([NSPy]ZnCl3) was prepared and used as a multipurpose catalyst for the synthesis of propargylamines by the A3 coupling reaction of aromatic aldehydes, alkynes, and secondary amines under mild conditions. In this reaction, the carbonyl group in the aldehyde was activated by the acidic part in the catalyst, and the C–H activation of phenylacetylene was carried out by zinc.
  Citation: Synlett ; : -
  PubDate: 2023-10-25T07:56:08+01:00
  DOI: 10.1055/s-0042-1751623
Solvent-Selective Synthesis of Diaryl Disulfides and Arylthio Acetic Acids
Using Thioglycolic Acid and Copper Catalysts
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  Authors: Kim; Kyungmi, Shin, Youngjin, Chae, Junghyun
  Abstract: An efficient Cu-catalytic protocol for the synthesis of diaryl disulfides from aryl iodides using thioglycolic acid as the sulfur source has been developed. This transformation was successful only in aqueous DMSO, and when the solvent system was switched to aqueous DMF, arylthio acetic acids, the immediate C–S coupling products, were obtained. Each synthetic protocol was optimized and applied to various aryl iodides to afford the corresponding products in good to excellent yields.
  Citation: Synlett ; : -
  PubDate: 2023-10-24T09:36:33+01:00
  DOI: 10.1055/a-2178-1701
Nanographenes Out of Planarity
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  Authors: Cruz; Carlos M., Campaña, Araceli G.
  Abstract: The combination of different distortion motifs in nanographenes and polycyclic conjugated hydrocarbons has been the focus of significant attention during the last decade. The continual discovery of multiple carbon allotropes has fueled the field. A plethora of research groups around the globe are engaged in developing methods for the preparation of discrete graphene or fullerene fragments and new carbon allotropes. The goal is to fully understand the structure–property relationships in these systems. Herein, we present our journey and contributions to the field, from the development of a synthetic methodology towards functionalized heptagon-containing hexa-peri-hexabenzocoronenes through the preparation of saddle-helix hybrid nanographenes, the study of heptagon-containing cumulenic and open-shell systems, nanographenes embedded with higher order carbocycles, and the study of their electronic properties on-surface and by single-molecule conductance.1 Introduction2 The Finding of a Cornerstone Scaffold3 Saddle-Helix Hybrid Nanographenes4 Cumulenic and Diradicaloid Systems5 Supramolecular Studies6 Octagon- and Nonagon-Embedded Nanographenes7 Molecular Electronics and On-Surface Studies8 Outlook
  Citation: Synlett ; : -
  PubDate: 2023-10-24T08:37:08+01:00
  DOI: 10.1055/a-2165-6497
Organophotocatalytic Radical–Polar Cross-Coupling of Styrylboronic Acids
and Redox-Active Esters
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  Authors: Brals; Jeremy, D’Arcy-Evans, Nicholas, McGuire, Thomas M., Watson, Allan J. B.
  Abstract: We report the development of a radical–polar cross-coupling reaction using styrylboronic acids and redox-active esters under organophotoredox catalysis. The reaction proceeds through a formal polarity-mismatched radical addition. The use of an organic photocatalyst permitted very low loadings of the electron-shuttle additive and accelerated reaction times compared with established processes. The scope of the reaction was explored, and the utility of the products is demonstrated.
  Citation: Synlett ; : -
  PubDate: 2023-10-23T13:22:21+01:00
  DOI: 10.1055/a-2179-6570
Redox-Tag-Guided Radical Cation Diels–Alder Reactions: Use of Enol
Ethers as Dienophiles
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  Authors: Morizumi; Haruka, Nakayama, Kaii, Kitano, Yoshikazu, Okada, Yohei
  Abstract: Although radical cation Diels–Alder reactions enable the formation of cyclohexene ring systems between electronically mismatched (both electron-rich) dienes and dienophiles, which is otherwise difficult or impossible to achieve under thermal conditions, the substrate scope has been limited. Herein, we disclose that a radical cation Diels–Alder reaction using an enol ether as an electron-rich (and therefore oxidizable) dienophile is possible through a rationally designed redox tag strategy. Electrochemical and TiO2 photochemical approaches are effective in driving the reaction, where both intermolecular and intramolecular electron transfers are the key.
  Citation: Synlett ; : -
  PubDate: 2023-10-23T11:13:32+01:00
  DOI: 10.1055/a-2161-9607
A Facile Synthesis of 3′-Fluoro Hexitol Adenosine and Guanosine
Phosphoramidites
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  Authors: Prakash; Thazha P., Yu, Jinghua, Vasquez, Guillermo, Allerson, Charels R., Swayze, Eric E.
  Abstract: We report a convenient and scalable synthetic approach for the synthesis of 3′-fluoro hexitol adenosine and guanosine nucleoside analogues and corresponding phosphoramidites in good yield. 1,5-Anhydro-4,6-O-benzylidene-d-glucitol was converted into 1,5-anhydro-4,6-O-benzylidene-3-deoxy-3-fluoro-2-O-trifluoromethanesulfonyl-d-altritol in a three-step process. Glycosylation using adenosine or 2-amino-6-iodopurine yielded the corresponding nucleoside analogues in excellent yield. Based on this strategy, a highly concise and scalable synthesis of 3′-fluoro hexitol purine nucleosides (1–2 g, 18–21% overall yield) was accomplished, which will enable the use of 3′-fluoro hexitol nucleic acids for genetic medicine development and diagnostic applications.
  Citation: Synlett ; : -
  PubDate: 2023-10-19T09:04:03+01:00
  DOI: 10.1055/s-0042-1751507
Chiral Bifunctional Sulfide-Catalyzed Enantioselective Synthesis of
α-Substituted γ-Lactones Bearing a γ-Quaternary Stereocenter
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  Authors: Mori; Taiki, Sumida, Sao, Furuya, Yasuaki, Shirakawa, Seiji
  Abstract: Catalytic highly enantioselective syntheses of α-spiro-γ-lactones and α-substituted γ-lactones bearing a γ-quaternary stereocenter have been achieved through chiral bifunctional sulfide-catalyzed asymmetric bromolactonizations. The synthetic utility of the optically active γ-lactone products was demonstrated by transformations into functionalized γ-lactones and epoxides possessing a quaternary stereocenter.
  Citation: Synlett ; : -
  PubDate: 2023-10-19T08:30:33+01:00
  DOI: 10.1055/a-2161-9513
Synthesis and Properties of 2′-Deoxyadenosine Mimics Bearing a
Thieno[3,2-d]pyrimidine Ring
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  Authors: Fuchi; Yasufumi, Kawaguchi, Miho, Ito, Yuta, Hari, Yoshiyuki
  Abstract: A C-nucleoside with a stable C–C glycosidic bond can be used as a building block for chemically modified oligonucleotides (ONs). In this study, two adenosine-like C-nucleosides (dSA and dSO2A) bearing thieno[3,2-d]pyrimidine rings were designed and synthesized. These analogues were synthesized via the Heck reaction, and their properties as monomer nucleosides were investigated. Both the dSA and dSO2A monomers were not recognized by adenosine deaminase (ADA). In addition, they exhibited fluorescence emissions in the UV and visible regions of dSA and dSO2A, respectively. Subsequently, dSA was converted into a phosphoramidite compound and incorporated into the ONs. The synthesized dSA-modified ONs formed a stable duplex with DNA and RNA complements comparable to natural adenosine. Furthermore, the modified ONs exhibited fluorescence emission derived from dSA.
  Citation: Synlett ; : -
  PubDate: 2023-10-18T11:55:56+01:00
  DOI: 10.1055/s-0042-1751508
Serendipitous Synthesis of 5-Hydroxyuridine from
2′,3′-O-Isopropylidene N4-Acetylcytidine by Hypervalent
Iodine(III)-Mediated Reaction
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  Authors: Maverick; Mary Anne, Noël, Mathieu, Vasseur, Jean-Jacques, Baraguey, Carine, Debart, Françoise, Smietana, Michael
  Abstract: Whereas BAIB-TEMPO oxidation of 2′,3′-O-TBDMS-N4-acetylcytidine results in the expected 5′-carboxylic acid nucleoside, its 2′,3′-O-isopropylidene analogue reacts in a radically different way. We have demonstrated here that hypervalent iodine(III) in water triggers an unprecedented oxidative cyclization leading to a mixture of C5-substituted O6,5′-cyclo-5,6-dihydrouridines. This mixture of cyclouridines can be opened under basic conditions and, after deprotection, yields 5-hydroxyuridine, an important post-transcriptional modification of uridine at the wobble position (U34) of bacterial tRNA. NMR experimental values and calculations were performed to provide further insight on the specific reactivity of 2′,3′-O-isopropylidene N4-acetylcytidine.
  Citation: Synlett ; : -
  PubDate: 2023-10-18T11:42:10+01:00
  DOI: 10.1055/a-2174-2554
Decagram-Scale Synthesis of
N-{2-[4-(β-d-Glucopyranosyloxy)-2-methylphenyl]-1,1-dimethyl-2-oxoethyl}-3-methylthiophene-2-carboxamide
(GPTC), a Metabolite of the Fungicide Isofetamid
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  Authors: Jang; Hongjun, Kwak, Soo Yeon, Kim, Young Hoon, Han, Jae-hyuk, Park, Youngjik, Baek, Seung-Hoon, Lee, Dongjoo, Kim, Hyoungsu
  Abstract: A decagram-scale synthesis of N-{2-[4-(β-d-glucopyranosyloxy)-2-methylphenyl]-1,1-dimethyl-2-oxoethyl}-3-methylthiophene-2-carboxamide (GPTC), a metabolite of the fungicide isofetamid, has been achieved in a highly straightforward manner from the known compound 1-(4-hydroxy-2-methylphenyl)-2-methylpropan-1-one in eight steps with a 20% overall yield to provide a standard certified reference material for residue analysis in food.
  Citation: Synlett ; : -
  PubDate: 2023-10-17T10:32:11+01:00
  DOI: 10.1055/a-2178-1442
Stereogenic π-Conjugated Macrocycles: Synthesis, Structure, and
Chiroptical Properties Including Circularly Polarized Luminescence
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  Authors: Hasegawa; Masashi, Mazaki, Yasuhiro
  Abstract: Highly symmetrical and aesthetically pleasing molecules have attracted the attention of organic chemists. We synthesized new highly symmetric stereogenic π-conjugated macrocycles with planar or axial chirality. Macrocyclic oligomers synthesized by Yamamoto coupling or Suzuki–Miyaura cross-coupling from the π-unit containing chirality. These cyclization reactions gave multiple oligomers in relatively high yields. We then elucidated their structures and investigated their chiroptical properties, including circular dichroism (CD) and circularly polarized luminescence (CPL). Because of the selection rule for rigid and symmetric structures, these macrocycles exhibit a high dissymmetry factor (g abs or g lum) for circularly polarized light in CD or CPL. Several rigid cyclic compounds retain a highly symmetric structure in the excited state and exhibit higher g lum values than common chiral organic compounds. This Account provides a brief background regarding chiroptical properties, followed by a summary of the various macrocycles synthesized in this study. We are glad if this Account will be a source of ideas not only for chemists working with π-conjugated compounds, but also for synthetic chemists working with chiral compounds, especially those engaged in asymmetric synthesis.1 Introduction2 Brief Description of Chiroptical Properties3 Stereogenic Macrocycle Based on [2.2]Paracyclophane3.1 Stereogenic Double-decker Oligothiophene3.2 Stereogenic Biselenophene Macrocycle3.3 Helical Oligophenylene Linked with [2.2]Paracyclophane4 Stereogenic Macrocycle Based on Binaphthyl4.1 Cyclic Oligomer of Chiral Binaphthyl4.2 Doubly Twisted Binaphthyl Dimer4.3 Cyclic Oligomer of Binaphthyl Extended with Paraphenylene4.4 Curved Helical Paraphenylene Anchoring Chiral Binaphthyl4.5 Binaphthyl-Hinged [5]-Helicene5 Summary
  Citation: Synlett ; : -
  PubDate: 2023-10-16T13:11:23+01:00
  DOI: 10.1055/a-2158-8820
Additive-Free Copper-Catalyzed Benzylic C(sp3)–H Carbamation: Simple
Preparation of Primary Benzylic Amines
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  Authors: Schmidt; William, Bakhoda, Abolghasem Gus
  Abstract: A simple and practical method for the synthesis of primary alkylamines by direct functionalization of hydrocarbons is described. The N-Boc-protected alkylamines are readily prepared from tert-butyl (trimethylsilyl)carbamate and N-fluorobenzenesulfonimide in the presence of a Cu(I) catalyst at low catalyst loadings. Advantageously, this process proceeds free of any additive such as auxiliary bases/acids, requires only one equivalent of the substrate, and does not require ligand synthesis. This operationally simple C–H carbamation method shows high site selectivity and good functional-group tolerance, and uses a commercially available Cu precatalyst and oxidant to furnish N-Boc protected alkylamines in yields of 16–83%. The products can be simply deprotected under mild acidic conditions to generate primary benzylic amines. This practical method was subsequently used for the synthesis of the active pharmaceutical ingredients cinacalcet and sertraline.
  Citation: Synlett ; : -
  PubDate: 2023-10-12T12:01:23+01:00
  DOI: 10.1055/a-2170-2630
Solvent Selection in the Detritylation Reaction for the Solid-Phase
Synthesis of Oligonucleotides
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  Authors: Li; Quanjian, Sanghvi, Yogesh S., Yan, Hongbin
  Abstract: This study examined the choice of solvent in the detritylation reaction for solid-phase oligonucleotide synthesis. In addition to being chemically inert under detritylation conditions, such a solvent should not bind with acid used in this reaction. These considerations explained the only two choices of solvent currently used in the detritylation reaction: dichloromethane and toluene. Other solvents, such as ethyl acetate, acetonitrile, THF, and nitromethane are shown by NMR spectroscopy to bind with trichloroacetic acid. Therefore, these are undesirable solvents for the detritylation reaction, confirmed by solid-phase synthesis experiments.
  Citation: Synlett ; : -
  PubDate: 2023-10-11T13:08:16+01:00
  DOI: 10.1055/s-0041-1738455
Nickel-Catalyzed Decarbonylation of α-Oxyacetic Acid Thioesters:
Hydroxymethylation of Mercaptans
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  Authors: Tian; Rui, Li, Jia-Xin, Zhu, Yong-Ming
  Abstract: A strategy for the Ni-catalyzed decarbonylation of α-oxyacetic acid thioesters is described, providing a new pathway for the synthesis of monosulfide acetals, and further proving that oxygen atoms can stabilize an α-carbocation and promote a decarbonylation reaction. This method has good functional-group compatibility and can tolerate a wide range of electron-withdrawing, electron-neutral, and electron-donating substituents. In addition, this method complements the conventional cross-coupling reactions.
  Citation: Synlett ; : -
  PubDate: 2023-10-11T10:29:01+01:00
  DOI: 10.1055/a-2159-4369
Sulfonated Graphene as a Sustainable Catalyst for Environmentally Benign
Preparation of Benzylidene Acetals of Carbohydrates
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  Authors: Rabha; Padmashri, Sharma, Anjali, Panchadhayee, Rajib
  Abstract: A clean and efficient method has been developed for the introduction of benzylidene acetals into carbohydrate derivatives catalyzed by sulfonated graphene at room temperature. Yields were excellent in each case. The catalyst can be reused several times without much decrease in reactivity.
  Citation: Synlett ; : -
  PubDate: 2023-10-11T10:11:54+01:00
  DOI: 10.1055/a-2166-0400
A Simple and Powerful tert-Butylation of Carboxylic Acids and Alcohols
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  Authors: Ogasa; Chie, Kayano, Kimika, Namba, Kosuke
  Abstract: A simple and safe tert-butylation reaction was developed. Treatment of various free amino acids with 1.1 equivalents of bis(trifluoromethanesulfonyl)imide in tert-butyl acetate directly afforded tert-butyl esters with free amino groups quickly and in good yields. In addition, various carboxylic acids and alcohols without amino groups were converted into tert-butyl esters and ethers, respectively, in high yields in the presence of small catalytic amounts of bis(trifluoromethanesulfonyl)imide. All tert-butylation reactions of free amino acids, carboxylic acids, and alcohols proceeded much faster and in higher yields compared with conventional methods.
  Citation: Synlett ; : -
  PubDate: 2023-10-09T12:07:42+01:00
  DOI: 10.1055/a-2161-9689
A Complementary Route for Alkene–Arene para-Cycloadditions by
Visible-Light-Promoted Triplet Sensitization of Allenamides
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  Authors: Serafino; Andrea, Maestri, Giovanni
  Abstract: The synthetic relevance of bicyclo[2.2.2]octadienes is witnessed by their successful application in various chemical domains, promoting a recurrent interest in the concise assembly of these bridged bicycles. Seminal examples of strategies to craft these compounds are presented, together with more-recent applications that exploit visible light. In this context, a general intramolecular method for the para-cycloaddition of an allenamide arm onto simple aryl rings is highlighted.
  Citation: Synlett ; : -
  PubDate: 2023-10-09T11:31:27+01:00
  DOI: 10.1055/a-2136-3947
Construction of Vicinal Stereocenters via Asymmetric Cyanosilylation
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  Authors: Huang; Zhongxing
  Abstract: Asymmetric cyanosilylation serves as an important tool to convert easily available ketones into cyanohydrins of diverse reactivity. Whereas a large library of organocatalysts and transition-metal catalysts have been identified for monoketones, cyanosilylation of more-complex substrates, particularly those giving enantioenriched vicinal stereocenters, is underexplored in comparison. Here, a pair of recently published kinetic resolution and desymmetrization methods are highlighted for their success in constructing complex vicinal stereocenters by cyanosilylation using tailored aluminum and magnesium catalysts, respectively.1 Introduction2 Kinetic Resolution of α-Branched Ketones3 Desymmetrization of 1,3-Diketones4 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-10-05T08:19:38+01:00
  DOI: 10.1055/a-2160-7887
Labeling of Highly Reactive Tetrazines using [18F]SuFEx
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  Authors: Battisti; Umberto M., Müller, Marius, García-Vázquez, Rocío, Herth, Matthias Manfred
  Abstract: Pretargeted imaging is an emerging technique to study the in vivo biodistribution of nanomedicines. Currently, the tetrazine ligation is considered the most promising bioorthogonal reaction for pretargeting. Recently, Zheng et al. described an ultrafast late-stage radiolabeling of tetrazines based on sulfur 18F-fluoride exchange click chemistry ([18F]SuFEx). However, bispyridyl and H-tetrazines—the most promising structures for in vivo pretargeted applications—cannot be labeled using the proposed reaction conditions as they lead to decomposition of the tetrazine core. Here, we report improved conditions, exploiting basic preconditioning conditions for the quaternary methyl ammonium (QMA) cartridge and the use of low basic anions that allow 18F-labeling of bispyridyl and H-tetrazines using SuFEx. This strategy resulted in fast and efficient radiolabeling of highly reactive tetrazines with radiochemical conversions of up to 85% and radiochemical purity above 95%. This opens up the possibility to use SuFEx to 18F-label tetrazines, which are suitable for in vivo pretargeted imaging.
  Citation: Synlett ; : -
  PubDate: 2023-10-04T11:08:01+01:00
  DOI: 10.1055/a-2147-9303
A Combination of Computational and Experimental Studies to Correlate
Electronic Structure and Reactivity of Donor–Acceptor Singlet Carbenes
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  Authors: Singh; Shweta, Gremaud, Ludovic, Sen, Subhabrata, Maiti, Debajit
  Abstract: Most of the reactivities of donor–acceptor (D–A) singlet carbenes are similar to metal carbenoids. However, the lone pair at the carbenoid carbon, coordinated with metal, is free in D–A carbene thereby making it nucleophilic as well. Herein, DFT-optimized structural features of D–A carbene has been investigated and is compared with rhodium carbenoid. It was observed that, when a D–A carbene reacts with cyclic-1,3-diones in different ethereal solvents, it is the lone pair at the sp2 orbital of the carbene that abstracts the proton from the enol form (of the cyclic-1,3-diones) to form a benzylic carbocation and an enolate. Subsequently, the carbocation undergoes nucleophilic attack by O of the ether solvents and then by the enolate to afford the desired ether-linked products. Accordingly, herein the reaction in THF, which otherwise had failed to work as a substrate in reported amino etherification reactions, worked well. DFT-calculated orbital energy levels and reaction profile support this reverse reactivity of singlet carbenes. Furthermore, HOMO–LUMO calculations indicated that electron-rich arenes in D–A carbene stabilizes the LUMO and destabilizes the HOMO which increases yield. Additionally, a library of 37 enol ether and 39 ether-linked compounds of potential medicinal relevance have been synthesized with good to excellent yields using numerous cyclic-1,3-diones.
  Citation: Synlett ; : -
  PubDate: 2023-09-28T12:57:26+01:00
  DOI: 10.1055/a-2153-6819
Visible-Light-Promoted Synthesis of Vinyloxaziridines from Conjugated
Carbonyls
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  Authors: Austin; Brooke E., Palner, Ryan P., Tobias, Elissa M., Madiu, Rufai, Doran, Erin L., Doran, Jenna M., Howard, Amari M., Stroud, James L., Rossi, Morgan E., Moskovitz, Dylan A., Rivera, Dominic A., Mullen, Michael D., Zinsky, Amy H., Rosario, Rose A., Moura-Letts, Gustavo
  Abstract: We report the first visible-light-promoted synthesis of vinyloxaziridines from simple conjugated nitrones. We have found that vinyl nitrones formed by the condensation reaction between conjugated carbonyls and hydroxylamines undergo visible-light-promoted energy-transfer isomerization to the respective vinyloxaziridines in very high yields and selectivities. The reaction scope expands to a large array of substitution patterns, and evidence indicates that the proposed energy-transfer pathway is the predominant mechanism for this transformation.
  Citation: Synlett ; : -
  PubDate: 2023-09-28T12:29:42+01:00
  DOI: 10.1055/a-2153-6687
Alternative Synthesis of α-l-Threofuranosyl Guanosine
3′-triphosphate
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  Authors: Sarma; Daisy, Majumdar, Biju, Chaput, John C.
  Abstract: Artificial genetic polymers (XNAs) have attracted considerable attention due to their unique physicochemical properties that include enhanced chemical and biological stability. Unfortunately, some of the most interesting XNAs are constructed from monomers that are not readily available and must be prepared by chemical synthesis. The need to generate building-block materials for these systems warrants careful optimization, as syntheses of XNA monomers can easily exceed ten chemical steps. Here, we evaluate the synthesis of α-l-threofuranosyl guanosine 3′-triphosphate (tGTP), a key substrate in the enzymatic synthesis of α-l-threofuranosyl nucleic acids. Previously, tGTP was prepared by a Vorbrüggen glycosylation reaction from N-acetyl-O-(diphenylcarbamoyl)guanine and a suitably protected threose sugar. However, the preparation of the protected nucleobase was a laborious process that merited further evaluation. We now describe an alternative approach that is easier to perform and does not compromise the overall yield or regioselectivity.
  Citation: Synlett ; : -
  PubDate: 2023-09-28T08:38:28+01:00
  DOI: 10.1055/s-0041-1738452
Multigram-Scale Synthesis of a gem-Difluoro-Substituted
4,5,6,7-Tetrahydrobenzo[c]thiophen-4-one Heterocycle via Oxidative
Chlorination and Radical Smiles Rearrangement
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  Authors: Henry; Martyn C., Anderson, Jack Q., Jamieson, Craig
  Abstract: We report an optimized synthetic route towards a functionalized 4,5,6,7-tetrahydrobenzo[c]thiophene heterocycle bearing a gem-difluoromethylene moiety in 4 steps with an overall yield of 43%. The CF2 fragment was incorporated using a building block approach, by coupling an appropriate fluorinated alcohol with a C-3 sulfonyl chloride, synthesized via oxidative chlorination of an exocyclic benzyl thioether. Visible-light-mediated Smiles rearrangement of the resulting fluorosulfonate ester then furnishes the desired fluorinated thiophene scaffold.
  Citation: Synlett ; : -
  PubDate: 2023-09-27T11:49:49+01:00
  DOI: 10.1055/a-2153-7341
Solvent Effect on Base-Free Synthesis 4-Substituted 2-Oxazolines via
Intramolecular Cyclodemesylation
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  Authors: Dalkılıç; Erdin, Güneş, Yakup
  Abstract: In this present study, the solvent effect was examined for the synthesis of 2-oxazolines via intramolecular cyclodemesylation. To determine the solvent effect, aprotic/protic polar and nonpolar solvents were screened and polar protic solvents met the best result. The remarkable feature of this synthesis is that cyclization takes place in the absence of any base or reagent, in high yields (89–96%). As a result, a series of 4-substituted chiral 2-oxazolines were successfully synthesized through a four-step process, with overall yields reaching between 79% and 88% in a greener approach.
  Citation: Synlett ; : -
  PubDate: 2023-09-19T09:50:44+01:00
  DOI: 10.1055/s-0042-1751491
Desulfonylative Radical Truce–Smiles Rearrangement Utilizing the
Benzimidazoline and Benzimidazolium Redox Couple
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  Authors: Miyajima; Ryo, Okamura, Manon, Oomori, Kazuki, Iwamoto, Hajime, Wakamatsu, Kan, Hasegawa, Eietsu
  Abstract: We have developed protocols for promoting redox reactions utilizing the 2-substituted 1,3-dimethylbenzimidazoline (BIH–R) and benzimidazolium (BI+–R) couples which were applied to the desulfonylative radical Truce–Smiles rearrangement. Expected rearrangement products formed in modest to good yields in these processes, in which added or in situ generated BIH–R serve as electron- and hydrogen-atom-donating reagents or photocatalysts. DFT calculations were carried out to gain the information about the radical intermediates involved in the rearrangement reaction.
  Citation: Synlett ; : -
  PubDate: 2023-09-19T09:39:15+01:00
  DOI: 10.1055/a-2153-6594
Insights into the Regioselectivity of Metal-Catalyzed Aryne Reactions
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  Authors: Plasek; Erin E., Denman, Brylon N., Roberts, Courtney C.
  Abstract: The synthetic potential of unsymmetrically substituted aryne intermediates is significantly hindered by regioselectivity issues. Current methods for inducing regioselectivity all rely on substrate control and are focused on non-metallated arynes. Before our initial disclosure, there was no systematic study regarding the regioselectivity of metal-catalyzed aryne reactions. By exploiting ligand control, we have induced regioselectivity in a palladium-catalyzed aryne annulation to form phenanthridinones (up to 9:91 r.r.). Through this study we have investigated: ligand effects, influence of steric perturbation, and the impact of the aryne precursor.1 Introduction2 Inducing Regioselectivity via Ligand Control3 A Comparison of o-Borylaryl Triflate Aryne Precursors to Kobayashi Aryne Precursors4 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-09-18T13:07:26+01:00
  DOI: 10.1055/s-0042-1751487
Development of Novel Catalytic Direct Syntheses of N-Unsubstituted
Ketimines and Their Applications to One-Pot Reactions
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  Authors: Kondo; Yuta, Morimoto, Hiroyuki, Ohshima, Takashi
  Abstract: Herein, we summarize our recent efforts toward developing catalytic methods for the synthesis of N-unsubstituted ketimines and their applications to one-pot reactions for producing various nitrogen-containing compounds. This account provides detailed background, optimization, scope, and mechanistic information. We hope this work will stimulate future studies on the implementation of N-unsubstituted ketimines.1 Introduction2 Scandium-Catalyzed Synthesis of N-Unsubstituted Ketimines3 Tetra-n-butylammonium Fluoride Catalyzed Synthesis of N-Unsubstituted Ketimines4 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-09-18T11:26:39+01:00
  DOI: 10.1055/a-2131-3448
Triangulenium Ions: Versatile Organic Photoredox Catalysts for
Green-Light-Mediated Reactions
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  Authors: Nowack; Marko H., Moutet, Jules, Laursen, Bo W., Gianetti, Thomas L.
  Abstract: The development of tunable organic photoredox catalysts remains important in the field of photoredox catalysis. A highly modular and tunable family of trianguleniums (azadioxatriangulenium, diazaoxatriangulenium, and triazatriangulenium), and the related [4]helicene quinacridinium have been used as organic photoredox catalysts for photoreductions and photooxidations under visible light irradiation (λ = 518–640 nm). A highlight of this family of photoredox catalysts is their readily tunable redox properties, leading to different reactivities. We report their use as photocatalysts for the aerobic oxidative hydroxylation of arylboronic acids and the aerobic cross-dehydrogenative coupling reaction of N-phenyl-1,2,3,5-tetrahydroisoquinoline with nitromethane through reductive quenching. Furthermore, their potential as photoreduction catalysts has been demonstrated through the catalysis of an intermolecular atom-transfer radical addition via oxidative quenching. These transformations serve as benchmarks to highlight that the easily synthesized trianguleniums, congeners of the acridiniums, are versatile organic photoredox catalysts with applications in both photooxidations and photoreductions.
  Citation: Synlett ; : -
  PubDate: 2023-09-18T11:03:56+01:00
  DOI: 10.1055/a-2117-8928
Recent Uses of Photogenerated Oxygen-Centered Radicals in Intermolecular
C–O Bond Formation
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  Authors: Banoun; Camille, Magnier, Emmanuel, Dagousset, Guillaume
  Abstract: We report herein recent advances made by our group and others in the field of oxygen-centered radicals generated under photocatalysis. Thanks to the design of new O-radical precursors, these radicals can now be efficiently trapped by unsaturated systems in an intermolecular manner, via the formation of a new C–O bond.1 Introduction2 Reactions Involving Carbonyloxy Radicals3 Reactions Involving Fluoroalkoxy Radicals4 Reactions Involving Alkoxy Radicals5 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-09-14T09:53:33+01:00
  DOI: 10.1055/a-2131-4126
Tunable Optical Properties and Self-Assemblies of a Water-Soluble
Perimidinium Imide Dye
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  Authors: Roy; Tirupati, Debnath, Indraneel, Mahata, Kingsuk
  Abstract: The synthesis of unsymmetrically peri-annulated naphthalene dyes, perimidinium imides (PrIm), is reported. Compared with the symmetrical and popular analogous naphthalenediimide dyes, PrIm showed a red-shifted absorption maximum. The water-soluble dyes showed tunable self-assembly behaviors and optical properties. The dyes retain their photoluminescence properties in water.
  Citation: Synlett ; : -
  PubDate: 2023-09-13T12:38:26+01:00
  DOI: 10.1055/a-2138-7080
Adventures in Total Synthesis – The Next Chapter
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  Authors: Chen; David Yu-Kai
  Abstract: This account summarizes the author’s endeavors in target-oriented synthesis at Seoul National University since 2011. A collection of the most celebrated molecules in total synthesis are revisited and the author’s solutions to these historical challenges are presented. In particular, the unique perception of their molecular frameworks and unprecedented bond-forming sequences form the basis of the newly developed strategies. Together with a ‘personal touch’ on these selected stories, the author hopes that this account will offer new insights and fresh perspectives for all levels of enthusiasts of target-oriented total synthesis.1 Introduction2.1 Synthesis of Strychnine2.2 Synthesis of Actinophyllic Acid2.3 Synthesis of Dendrobine2.4 Synthesis of Communesin2.5 Synthesis of Morphinans2.6 Synthesis of Reserpine2.7 Synthesis of Quinine and Quinidine2.8 Synthesis of Haouamine2.9 Future Work3 Summary and Outlook4 Abbreviations
  Citation: Synlett ; : -
  PubDate: 2023-09-13T11:33:53+01:00
  DOI: 10.1055/a-2145-3647
Aminoacylation of Alkenes by Cooperative NHC and Photoredox Catalysis
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  Authors: Lezius; Lena, Reimler, Jannik, Döben, Nadine, Hamm, Michael, Daniliuc, Constantin G., Studer, Armido
  Abstract: Cooperative NHC and photoredox catalysis has gained significant attention as an emerging research field in recent years. Herein, we report a cyclizing aminoacylation of alkenes, which is enabled through the combination of these two catalytic modes. The key step is a radical/radical cross-coupling between a persistent ketyl radical and a transient benzylic or aliphatic C-radical, which is generated through radical cyclization of an oxidatively formed amidyl radical. Several carbamates, amides and sulfonamides containing an alkene moiety and different acyl fluorides can be used as substrates. The resulting products are obtained in moderate to good yields.
  Citation: Synlett ; : -
  PubDate: 2023-09-12T09:28:14+01:00
  DOI: 10.1055/a-2145-8697
Visible-Light-Driven Denitrogenative C–C Bond Formation and Oxidative
Difunctionalization of Vinyl Azides
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  Authors: Sardar; Santosh Sing, De, Aramita, Pal, Satyajit, Sarkar, Subhankar, Santra, Sougata, Zyryanov, Grigory V., Majee, Adinath
  Abstract: A newer synthetic protocol has been developed to synthesize α-oxyalkyl ketones from vinyl azides under transition-metal-free reaction conditions. The reaction proceeds in the presence of organic photoredox catalyst rose bengal, an oxidant tert-butyl hydroperoxide (TBHP), and ethers. A broad range of substituted vinyl azides were found to react smoothly upon visible-light irradiation, which readily furnished the related products. Several control experiments have been done to suggest a probable mechanism. The process is initiated by radical addition to vinyl azide, which triggers a cascade fragmentation mechanism driven by the loss of dinitrogen and the stabilized ether radical ultimately produces the α-oxyalkyl ketones. This method provides a simple, mild, straight forward, novel paradigm to prepare α-oxyalkyl ketones.
  Citation: Synlett ; : -
  PubDate: 2023-09-12T09:04:21+01:00
  DOI: 10.1055/a-2131-3208
Acetate/Alkoxide/Halide Shuttle Systems Mediated by Lewis Acid Catalysts
for Insertion Reaction of a One-Carbon Unit into Carbon–Carbon or
Carbon–Halogen Bonds
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  Authors: Nishimoto; Yoshihiro, Yasuda, Makoto
  Abstract: In this account, we describe our research on a Lewis acid-catalyzed insertion reaction of α-diazo esters into a carbon–carbon or carbon–halogen bond. Indium catalysts mediated not only the insertion of α-diazo esters into a carbon–carbon bond of alkyl acetates, alkyl ethers, acetals, and alkyl halides, but also a carbon–halogen bond of alkyl chlorides, bromides, and iodides. BF3 specifically accelerated the insertion of α-diazo esters into a carbon–fluorine bond. The key to this catalysis is acetate, alkoxide, and halide shuttle systems mediated by a Lewis acid, in which the Lewis acid abstracts a leaving group from a starting substrate and releases the leaving group to the appropriate carbocation intermediate in the catalytic cycle.1 Introduction2 Acetate/Alkoxide Shuttle: Insertion Reaction of α-Diazo Esters into a Carbon–Carbon Bond of Alkyl Acetates, Alkyl Ethers, and Acetals3 Halide Shuttle: Insertion Reaction of α-Diazo Esters into a Carbon–Carbon Bond of Alkyl Halides4 Halide Shuttle: Insertion of α-Diazo Esters into a Carbon–Halogen Bond of Alkyl Halides5 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-09-11T11:36:06+01:00
  DOI: 10.1055/a-2136-3609
Anthracene-Functionalized Metallacage with Fluorescence Response Behavior
to Anions
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  Authors: Zeng; Zhi-Yong, Zhao, Xiaoli, Huang, Junhai, Zhu, Jing, Jin, Tongxia, Hu, Lianrui, Dou, Wei-Tao, Xu, Lin
  Abstract: Functionalized metallacages have attracted tremendous attention in recent years due to their potential applications in optical sensing, catalysis, and recognition. A novel anthracene-functionalized metallacage was synthesized and characterized in detail by UV/vis spectroscopy, 1D/2D NMR, electrospray ionization time-of-flight mass spectrometry, and X-ray single crystal diffraction. This metallacage exhibited a specific fluorescence enhancement response to OH–, PO4 3–, and AcO– anions, and further analysis indicated that this was due to anion-induced metallacage disassembly.
  Citation: Synlett ; : -
  PubDate: 2023-09-07T13:31:52+01:00
  DOI: 10.1055/s-0042-1751486
Iron-Catalyzed Oxidative Decarboxylation of Oxamic Acids: A Safe and
Efficient Photochemical Route to Urethanes
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  Authors: Kurtay; Gülbin, Lusseau, Jonathan, Robert, Frédéric, Landais, Yannick
  Abstract: This study presents a facile method for synthesizing urethanes through the photocatalyzed oxidative decarboxylation of oxamic acids. The process involves the formation of an isocyanate in situ from an oxamic acid under blue-light irradiation (427 nm) in the presence of ferrocene as a photocatalyst, 2-picolinic acid as a ligand, and potassium bromate as an oxidant. The one-pot procedure effectively avoids the need for separation, purification, and storage of carcinogenic isocyanates, making it a safer and more practical method for obtaining target urethanes from easily accessible starting materials.
  Citation: Synlett ; : -
  PubDate: 2023-09-07T11:10:43+01:00
  DOI: 10.1055/a-2131-3368
Exploring the Power of Sulfur, Silicon, and Organocatalysis: Innovative
Strategies for Asymmetric Synthesis and Advanced Synthetic Methodology
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  Authors: Chiu; Kuei-Wei, Chein, Rong-Jie
  Abstract: This research Account describes the development of chiral organocatalysts, focusing on diphenyl-2-pyrrolidinemethanol and its derivatives as valuable tools in asymmetric transformations. The research also includes the discovery of a novel anionic Si→C alkyl migration method, which has been developed into a one-pot procedure for synthesizing (E)-chalcones from hydroxyamide and N,N-diethylcarbamates. The findings underscore the potential of sulfide and silicon as valuable reagents for organic synthesis and emphasize the importance of exploring new reaction pathways and mechanisms to discover novel synthetic methods.1 Introduction2 Synthesis of 2 and Sulfur Reagent as Chiral Lewis Acid3 Sulfur/Selenium Reagent as Chiral Lewis Base4 Anionic Si→C Alkyl Migration5 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-09-06T11:37:40+01:00
  DOI: 10.1055/a-2099-6478
Practical Asymmetric Synthesis of Sulfoximines and Sulfimides from
Sulfinamides
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  Authors: Tsuzuki; Saori, Kano, Taichi
  Abstract: Chiral sulfoximines and sulfimides are an interesting class of compounds in various areas. However, methodologies for preparing these chiral sulfur compounds in a stereoselective manner have been underdeveloped. Herein, we briefly summarize our recent studies on asymmetric synthesis of sulfoximines and sulfimides from readily available enantioenriched sulfinamides. In these studies, optically pure sulfoximines and sulfimides having various carbon substituents on their sulfur atom could be obtained.1 Introduction2 Asymmetric Synthesis of Chiral Sulfoximines3 Asymmetric Synthesis of Chiral Sulfimides4 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-09-05T11:52:52+01:00
  DOI: 10.1055/a-2127-1260
Synthesis of P-Chiral Tertiary Phosphine Oxides by Copper-Catalyzed
Dynamic Kinetic Asymmetric C–P Cross-Coupling
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  Authors: Kang; Jie, Ren, Simu, Su, Bo
  Abstract: P-Stereogenic phosphorus compounds are of importance in various areas. Some strategies have been developed for the enantioselective formation of C–P bonds, among which transition-metal-catalyzed asymmetric C–P cross-coupling of secondary phosphine oxides (SPOs)—bench-stable, odorless, and nontoxic—is more appealing. Due to the elusive racemization of SPOs, reactions with them usually proceed in a kinetic resolution fashion, thus being less practical. Highlighted here is a copper-catalyzed, highly enantioselective dynamic kinetic intermolecular C–P coupling of SPOs and aryl iodides. The successful development of this reaction relies on two key factors: the facile racemization of SPOs under the reaction conditions and the high enantioselectivity of the carefully tuned copper catalysts. P-Stereogenic tertiary phosphine oxide (TPO) products were obtained in high yields and with good enantioselectivities and were further converted into structurally diverse P-chiral scaffolds that are highly valuable as ligands and catalysts in asymmetric synthesis.
  Citation: Synlett ; : -
  PubDate: 2023-09-05T11:18:31+01:00
  DOI: 10.1055/a-2127-1305
Nickel-Catalyzed Transesterification of Methyl Esters
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  Authors: Zheng; Yan-Long, Daneshfar, Omid, Li, Jia-Yi, Masson-Makdissi, Jeanne, Pinault-Masson, Émile, Newman, Stephen G.
  Abstract: A transesterification of methyl esters with aliphatic alcohols was developed using Ni/dcype catalysis. This reaction features the cleavage of the strong C(acyl)–OMe bond in the absence of acidic or basic additives, providing volatile methanol as the only stoichiometric waste product. A wide range of (hetero)aromatic and aliphatic methyl esters can be converted into the corresponding functionalized esters in good to excellent yields with high efficiency. Compared with traditional transesterifications, this cross-coupling approach offers new opportunities for efficient and chemoselective synthesis.
  Citation: Synlett ; : -
  PubDate: 2023-09-04T14:53:20+01:00
  DOI: 10.1055/s-0042-1751485
Enamine N-Oxides: Design, Synthesis, and Function in Bioorthogonal
Reactions
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  Authors: Kang; Dahye, Kim, Justin
  Abstract: Enamine N-oxides act as a chemical linchpin bridging two bioorthogonal associative and dissociative reactions. This article describes the design of enamine N-oxides, their synthesis through the retro-Cope elimination reaction, the use of solvent, hyperconjugation, strain, and rehybridization effects to achieve bioorthogonal reactivity, and their rapid reductive cleavage with diboron reagents. The coordinated assembly and disassembly of the enamine N-oxide motif constitutes a powerful chemical operation that enables the attachment and detachment of small molecules from biomacromolecules in a biological setting.1 Introduction2 Background3 General Access to Linear Enamine N-Oxides4 Strain-Promoted Hydroamination Reaction5 Electronically Activated Alkynes6 Chemically Revertible Reactions7 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-09-04T14:21:38+01:00
  DOI: 10.1055/a-2127-1086
A Computational and Experimental Analysis of Aldehyde Photooxidation
Driven by Visible Light in a Homemade Reactor
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  Authors: Cervantes-González; Javier, Mora-Rodríguez, Salma E., Benitez-Puebla, Luis J., López-Caamal, Fernando, García-Revilla, Marco A., Vázquez, Miguel A., Lagunas-Rivera, Selene
  Abstract: A computational and experimental analysis of HAT mechanism to obtain carboxylic acid via photooxidation of aldehyde is described, using a homemade reactor. The considered photocatalysts are organic dyes such as 2-chloroanthraquinone (2-ClAQN), rhodamine 6G (Rh6G), fluorescein (Fl), and eosin B (EOB); and the light spectrum is that of the visible light.
  Citation: Synlett ; : -
  PubDate: 2023-09-04T13:50:56+01:00
  DOI: 10.1055/a-2131-4033
Recent Developments in Photocatalytic Reduction of Nitro Compounds to
Valuable Scaffolds
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  Authors: Aggarwal; Varun, Bala, Ekta, Saima, Saima, Pathan, Sameer, Guleria, Saksham, Sharma, Sakshi, Selvaraj, Manickam, Verma, Praveen Kumar
  Abstract: The reduction of nitro compounds is one of the fundamental organic transformations and ascertain wide applicability in industrial chemistry, synthesis of valuable scaffolds, fine chemical synthesis, as well as environmental applicability for decontamination process. The transformation involves the conversion of nitro compounds into valuable scaffolds including amino, nitroso, hydroxyl amines, azo, and hydrazo compounds. Conventional approaches for the reduction of nitro compounds involves the environmentally harmful stoichiometric reagents, high-boiling reaction media, tedious processes, and harsh reaction conditions with high temperature and pressure. Additionally, the selectivity always remains a serious concern associated with the process due to the possibilities of several stable intermediate formation in the reaction pathway of reduction of nitro compounds. Nitro compounds are also of serious environmental concerns being a part of most harmful and high-priority classes of pollutants mainly released from industrial effluents, agricultural waste, and human sewage. A simple degradation of these pollutants bearing nitro group just removes the pollutants, however, the selective reduction of nitro group to valuable functionalities as mentioned above provides the industrially important scaffolds. With the advent of photocatalytic organic transformation, most of the scientific fraternity working in the area of organic synthesis, catalysis, and environmental decontaminations are utilizing the clean, green, low-temperature, energy and cost-effective, sustainable processes for the reduction of nitro compounds to access valuable scaffolds. Nowadays a lot of mechanistic developments in the field ease the processes for the developments of such highly valuable organic transformations. Herein, the present Account is focused on the recent developments in the photocatalytic reduction of nitro compounds to valuable scaffolds.1 Introduction2 Reduction of Nitro Compounds2.1 Conventional Approaches for Reduction of Nitro Compounds2.2 General Photocatalytic Mechanism3 Mechanistic Pathways: Electrochemical, Conventional and Photocatalytic Approaches3.1 Mechanism of Electrochemical Reduction of Nitroarene3.2 Conventional Reduction Mechanism of Nitroarenes3.3 General Photocatalytic Reduction Mechanism of Nitroarenes4 Photocatalytic Reduction of Nitro Compounds to Valuable Scaffolds4.1 Reduction of Nitro Compounds to Corresponding Amines4.2 Reduction of Nitro Compounds to Azo Compounds4.3 Reduction of Nitro Compounds to Azoxy Compounds4.4 Reduction of Nitro Compounds to Nitroso Compounds4.5 Reduction of Nitro Compounds to Hydroxyl Amines5 Future Perspective6 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-09-04T08:48:05+01:00
  DOI: 10.1055/a-2122-8508
Transition-Metal-Free and Photocatalyst-Free Sulfenylation of
Halopyrazolamines under Visible-Light Irradiation via Electron
Donor–Acceptor Complexes
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  Authors: Shanthi; Markabandhu, Perumal, Karuppaiah, Sivalingam, Soumya, Puhazhendhi, Arulmozhi, Kumar Mandali, Pavan, Ramesh, Subburethinam
  Abstract: A new approach was developed for the thiolation of halogenated pyrazole-5-amines under blue LED irradiation in metal-free conditions. This efficient and practical approach enabled the generation of thiolated pyrazol-5-amine building blocks of medicinal significance. This straightforward technique permits photochemical thiolation by an electron donor–acceptor by two distinct processes; formation of a charge-transfer complex through a halogen bond or π–π interaction based on various halogenated pyrazolamines, depending on the HOMO–LUMO energy gap of the C–X bond. The reaction of halogenated pyrazol-5-amines with thiophenol derivatives proceeded in good to excellent yields. The formation of a π–π complex or halogen bonding between the halopyrazolamine and the thiolate anion was confirmed by UV/visible spectroscopy.
  Citation: Synlett ; : -
  PubDate: 2023-08-31T14:20:31+01:00
  DOI: 10.1055/a-2136-3700
p-Block Element Catecholates: Lewis Superacidic, Constitutionally Dynamic,
and Redox Active
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  Authors: Greb; Lutz
  Abstract: Numerous strategies for enhancing the reactivity and properties of p-block elements have been devised in the past decades. This Account discusses our approaches by distinct ligand control on p-block elements in their normal (group) oxidation states. Catecholato ligands on silicon, germanium, or phosphorus produce a range of rewarding properties. Substantial electron withdrawal paired with structural constraint effects (influence of deformation energy) impart Lewis superacidity to these abundant elements. The ease of synthesis of such species facilitates screening in catalysis, promising a range of applications by powerful bond activation. Low-barrier Si–O/Si–O bond metathesis provides the most abundant bond in our Earth’s crust, with adaptive features under mild conditions, and establishes a new branch of constitutional dynamic chemistry. The redox-active character of catecholates grants access to novel compounds with tunable open-shell features. Overall, p-block catecholates offer unique opportunities due to their versatile features that will enrich the chemistry of the main-group elements.1 Introduction2 Halogenated Catecholates at Silicon Cause Substantial Lewis Acidity3 Constitutional Dynamics Cause a Structural Mystery4 Strong Silicon Lewis Acids Allow the Exploration of Uncharted Structures, Bond Activations, and Catalysis5 The Catechol Approach on Other Elements: Germanium and Phosphorus6 Catechols Are Redox Active: Also at Silicon7 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-08-29T14:22:27+01:00
  DOI: 10.1055/a-2122-8238
Small Aromatics Bearing Two Diarylamino Termini: Highly Reducing Organic
Photocatalysts
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  Authors: Koike; Takashi
  Abstract: Small aromatics such as anthracene, naphthalene, or benzene bearing two diarylamino termini function as highly reducing organic photocatalysts (OPCs). In particular, the small aromatic core remarkably enhances the reducing power of the catalyst in the excited state. An appropriate combination of an OPC and an electron-accepting fluoroalkylating reagent is the key to successful radical fluoroalkylation. The basic design of the photocatalyst and the photocatalytic fluoroalkylation of olefins are discussed.1 Introduction2 Basic Catalyst Design and Photo- and Electrochemical Properties3 Photocatalytic Reactions of 9,10-Bis(diphenylamino)anthracene Derivatives4 Photocatalytic Reactions of 1,4-Bis(diphenylamino)naphthalene Derivatives5 Photocatalytic Reactions of 1,4-Bis(diphenylamino)benzene6 Summary and Outlook
  Citation: Synlett ; : -
  PubDate: 2023-08-22T12:15:00+01:00
  DOI: 10.1055/a-2126-1897
Photoredox Defluorinative Silylation of α-Trifluoromethyl Arylalkenes
Using Silacarboxylic Acids as Silyl Radical Precursors
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  Authors: Zhang; Yi, Nie, Guihua, Jin, Zhichao, Ren, Shichao
  Abstract: A photoredox defluorinative silylation of α-trifluoromethyl arylalkenes for rapid access to useful gem-difluoroalkenes is disclosed. Stable and easily prepared silacarboxylic acids are used as silyl radical precursors in a photocatalytic decarboxylative process. The mild conditions and operational simplicity make our method a straightforward strategy to construct gem-difluoroalkenes bearing various functional groups, and a powerful strategy for incorporating a gem-difluoroalkene moiety into natural products and drug molecules.
  Citation: Synlett ; : -
  PubDate: 2023-08-21T10:48:33+01:00
  DOI: 10.1055/a-2122-8406
Effects of Electron-Donor and Counter-Cation in Photoinduced Deboronative
and Decarboxylative Aryl Radical Generation Using Two-Molecule Photoredox
Catalysts
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  Authors: Hashimoto; Ryoga, Furutani, Toshiki, Suzuki, Hirotsugu, Yoshimi, Yasuharu
  Abstract: In this study, we investigated the effects of electron-donors and counter-cations on the visible-light-induced deboronation and decarboxylation of arylboronic acid derivatives and benzoic acids using two-molecule photoredox catalysts. Different efficiencies in aryl radical generation were observed upon replacing the electron-donor and counter-cation. The rate of photoinduced deboronation of arylboronic acid derivatives strongly depends on the substituent, whereas the influence of counter-cation (Na+ and K+) was relatively minor. In the case of the benzoate ion derived from benzoic acid, the effect of both substituent and counter-cation decreases because of the complex mechanism. Additionally, the dependence of the oxidation ability of the radical cation on the electron-donor suggests the possibility of roughly estimating the oxidation potentials of the arylborate and benzoate ions.
  Citation: Synlett ; : -
  PubDate: 2023-08-17T08:19:51+01:00
  DOI: 10.1055/a-2117-9803
Functionalized Aza-BODIPYs and Their Use in the Synthesis of
Aza-BODIPY-Based Complex Systems
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  Authors: Yadav; Bharti, Ravikanth, Mangalampalli
  Abstract: In this account, we present syntheses of various functionalized aza-boron-dipyrromethene dyes (aza-BODIPYs) in which the functional groups are directly introduced at the 2- or 6-positions of the aza-BODIPYs or on aryl rings present at the 1-, 3-, 5-, and 7-positions of the aza-BODIPYs. Some of these functionalized aza-BODIPYs have been used for the synthesis of aza-BODIPY-based energy-transfer cassettes and light-harvesting complexes.1 Introduction2 Monofunctionalized Aza-BODIPYs2.1 2-/6-Monofunctionalized Aza-BODIPYs2.2 1-/3-/5-/7-Monofunctionalized Aza-BODIPYs3 Difunctionalized Aza-BODIPYs.3.1 2,6-Difunctionalized Aza-BODIPYs3.2 3,5-Difunctionalized Aza-BODIPYs3.3 1,7-Difunctionalized Aza-BODIPYs4 Miscellaneous5 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-08-17T07:41:38+01:00
  DOI: 10.1055/s-0042-1751480
Photochemical Reaction of 1,2-Naphthoquinone toward Enantioselective
Synthesis of γ-Rubromycin: Viability Dependence on Chromophore
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  Authors: Ando; Yoshio, Ogawa, Daichi, Wakita, Fumihiro, Suzuki, Keisuke, Ohmori, Ken
  Abstract: Aiming at the enantioselective total synthesis of γ-rubromycin, we reported the photochemical reaction of 1,2-naphthoquinone as a promising solution to otherwise-difficult enantiocontrol of the single spiroacetal stereogenic center. The present study examined the applicability of this approach to more functionalized substrates, which revealed viability dependence on the chromophore structure differing in the position and number of methoxy substituents.
  Citation: Synlett ; : -
  PubDate: 2023-08-14T12:22:46+01:00
  DOI: 10.1055/a-2113-0212
Photocatalytic 1,4-Addition of Aromatic Aldehydes or Ketones via Umpoled
Carbinol Anions
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  Authors: Okumura; Shintaro, Takahashi, Teruki, Torii, Kaoru, Uozumi, Yasuhiro
  Abstract: A 1,4-addition reaction of aromatic aldehydes or ketones to electron-deficient olefins was achieved under photocatalytic conditions. In the reaction, an umpoled carbinol anion generated in situ through two successive one-electron reductions of the carbonyl compound reacted nucleophilically with the electron-deficient olefin. Various electron-deficient aromatic aldehydes and ketones successfully underwent the reaction to afford the corresponding γ-functionalized alcohols.
  Citation: Synlett ; : -
  PubDate: 2023-08-14T12:22:40+01:00
  DOI: 10.1055/a-2122-8631
Enantioselective Palladium-Catalyzed Suzuki–Miyaura Reactions Enabled by
Ionic Ligand–Substrate Interactions
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  Authors: On; Ivan K. W., Zhu, Ye
  Pages: Abstract: Enzymes harness an array of noncovalent interactions to accomplish stereospecific transformations. Similarly, chemists have engineered chiral catalysts capable of eliciting noncovalent interactions for asymmetric synthesis. In this context, incorporating ionic groups into synthetic transition-metal catalysts represents a promising design element for enantioselective reactions by engaging electrostatic interactions between ligands and substrates. However, the nondirectional nature of ionic interactions presents a unique challenge in precise transmission of chirality. This account summarizes our recent work on developing phosphine ligands possessing nonligating ionic groups for exerting long-range stereocontrol in Suzuki–Miyaura reactions.1 Introduction2 Remote Quaternary Stereocenters3 Mechanically Planar Chiral Rotaxanes4 Atropo-enantioenriched Biaryls5 Conclusions
  Citation: Synlett ; : -
  PubDate: 2023-08-04T08:07:48+01:00
  DOI: 10.1055/a-2112-9552
Copper-(Photo)Catalyzed Radical Reactions with Organic Halides
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  Authors: Evano; Gwilherm, Theunissen, Cédric
  Pages: Abstract: Copper is one of the most efficient and attractive metals for catalysis. In addition to their availability, low cost and limited toxicity, copper complexes are utilized to catalyze a broad variety of reactions, including examples involving radicals. For such reactions, organic halides are by far the most versatile and attractive substrates. Our contributions to the catalysis of radical reactions from organic halides with copper complexes are summarized in this account.1 Introduction2 Copper-Catalyzed Radical Cross-Coupling Reactions3 Copper-Catalyzed Radical Reactions4 Copper-Catalyzed Radical Carbonylative Cross-Coupling Reactions5 Photoinduced, Copper-Catalyzed Radical Reactions6 Conclusions and Outlook
  Citation: Synlett ; : -
  PubDate: 2023-08-03T11:42:22+01:00
  DOI: 10.1055/a-2095-5242
Dual Responses of Fluorescence and Circular Dichroism for Antibiotics by a
Cationic Cage in Water
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  Authors: Dong; Yunhong, Cheng, Lin, Duan, Yanjuan, Xu, Huiru, Dong, Ruonan, Guo, Baolin, Cao, Liping
  Pages: Abstract: A tetraphenylethene (TPE)-based cationic cage (1) can form a 1:2 host–guest complex with antibiotics in water and imparts dual responses of fluorescence and circular dichroism (CD) to antibiotics based on the fluorescence and adaptive chiral conformation of the TPE units. Moreover, the host–guest complexes 1⊃(antibiotic)2 exhibited good antibacterial activity.
  Citation: Synlett ; : -
  PubDate: 2023-08-03T11:42:17+01:00
  DOI: 10.1055/a-2109-0055
Simple and Efficient Synthesis of Highly Functional
2-Oxonicotinonitriles from 2-Chloronicotinonitriles
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  Authors: Bardasov; Ivan N., Alekseeva, Anastasiya U., Sorokin, Saveliy P., Shishlikova, Maria A., Ershov, Oleg V.
  Pages: Abstract: A simple strategy for the synthesis of 2-oxo-1,2-dihydropyridine-3-carbonitrile derivatives (2-oxonicotinonitrile, 3-cyanopyridone) in good yields by substituting the halogen atom with an oxime under mild conditions was developed. The proposed approach makes it possible to avoid the problems associated with the hydrolysis of easily modified groups, since the reaction is carried out in the absence of water.
  Citation: Synlett ; : -
  PubDate: 2023-08-03T11:42:12+01:00
  DOI: 10.1055/a-2106-5177
Sulfoximines as S-Aryl Surrogates: A Photocatalytic Rapid, Metal-Free,
Mild Protocol to Access 3-Arylsulfenyl Indoles
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  Authors: Priya; V R Padma, Mercy, A Antony Haritha, Natarajan, K, Nandi, Ganesh Chandra
  Pages: Abstract: Sulfoximines as S-aryl surrogates permit the preparation of 3-arylsulfenylindoles through reaction with indoles in the presence of I2 under visible-light irradiation. This environmentally friendly approach is fast, mild, metal-, photocatalyst-, additive-, and oxidant-free, and it provides the desired products in moderate to good yields with a wide substrate scope.
  Citation: Synlett ; : -
  PubDate: 2023-07-31T09:09:41+01:00
  DOI: 10.1055/a-2107-5396
Regiodivergent Synthesis of Brominated Pyridylthiophenes by Overriding the
Inherent Substrate Bias
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  Authors: Hosoya; Masahiro, Mori, Atsunori, Okano, Kentaro
  Pages: Abstract: A regiocontrolled functionalization of a pyridylthiophene scaffold was accomplished. Regioselectivity for deprotonation of the pyridylthiophene was switched by changing the reaction conditions, including the metal amide base and the solvent. Subsequently, in situ transmetalation and halogen dance on the corresponding organometallic species were controlled by additives and the reaction temperature, as well as by the above reaction conditions. This method successfully enabled the synthesis of four iodinated constitutional isomers from a single starting material, 2-(5-bromo-2-thienyl)pyridine.
  Citation: Synlett ; : -
  PubDate: 2023-07-24T11:07:52+01:00
  DOI: 10.1055/a-2106-1678
Synthesis of Carbamoyl Azides from Redox-Active Esters and TMSN3
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  Authors: Yuan; Xiaobin, Qu, Yanjie, Li, Yajun, Bao, Hongli
  Pages: Abstract: An efficient method for construction of C–N bonds is reported here. The iron-catalyzed azidation of N-hydroxy phthalimide (NHP) esters provides a convenient approach for the synthesis of carbamoyl azides with good substrate scope and functional group tolerance. Both aryl carbon C(sp2) and alkyl carbon C(sp3) sources can be used deliver the carbamoyl azides. Mechanistic studies were conducted and a two-stage process was identified.
  Citation: Synlett ; : -
  PubDate: 2023-07-21T11:15:25+01:00
  DOI: 10.1055/a-2106-5108
Photo-Induced Glycosylations Using Organophotoacids: A New Environmentally
Benign Carbohydrate Synthesis
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  Authors: Toshima; Kazunobu, Takahashi, Daisuke, Isozaki, Yuka
  Abstract: This account reports the glycosylation reactions of glycosyl trichloroacetimidates and various alcohols using several organophotoacids as activators under photo-irradiation conditions. The reactions proceed smoothly to give the corresponding glycosides in high yields. The organophotoacids can be recovered and reused many times without any loss of efficiency, which demonstrates their environmentally benign features. 1 Introduction2 Photo-Induced Glycosylation Using Naphthol Derivatives3 Photo-Induced Glycosylation Using Aryl Thioureas4 Photo-Induced Glycosylation Using Diaryldisulfides5 Photo-Induced Glycosylation Using Diarylthiophenes6 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-07-21T10:24:16+01:00
  DOI: 10.1055/s-0042-1751477
Synthesis and Evaluation of Saponins with All-Nitrogenated Sugars
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  Authors: Kage; Ayaha, Okuyama, Yuya, Kato, Erina, Matagawa, Tomoe, Kawano, Sayaka, Simizu, Siro, Chida, Noritaka, Okamura, Toshitaka, Sato, Takaaki
  Pages: Abstract: Saponins exhibit multiple biological and pharmacological activities, and the sugar moiety of saponins is known to play a crucial role in bioactivity. In this report, we focus on the synthesis and evaluation of saponins with all-nitrogenated sugar (ANS), in which all oxygen atoms are replaced with nitrogen atoms. OSW-1 derivative-, cholesterol-, and diosgenin-ANS glycosides are synthesized by glycosylation with ANS in the presence of TMSOTf. As a result, the OSW-1 mimic, with ANS, exhibits good cytotoxic activity (IC50 = 7.31 μM) and induces apoptosis.
  Citation: Synlett ; : -
  PubDate: 2023-07-21T09:49:42+01:00
  DOI: 10.1055/a-2106-1345
Sustainable Organocatalytic Processes to Access Alkyl SuFEx Click Hubs and
Tetrasubstituted Carbon Centers: Potential Libraries for Multidisciplinary
Applications
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  Authors: Kim; Woo Hee, Park, Jin Hyun, Lee, Sun Bu, Israr, Muhammad, Koo, Byeong Jun, Kim, Soo Bok, Kim, Soyeon, Bae, Han Yong
  Pages: Abstract: In this Account, we provide an overview of our recent achievements on sustainable organocatalysis. Our group has unveiled the effectiveness of specific organocatalysts under various environmentally benign conditions. We have found that N-heterocyclic carbene and phosphazene superbases exhibit favorable performances in bulk aqueous reaction environments. In addition, the use of organic superacid catalysts results in synergistic effects when hydrogen-bond donor catalysts are assembled in aqueous media. Moreover, we discovered that a neutral organic salt precatalyst can generate a potent silylium Lewis acid catalyst in situ, specifically under solvent-free conditions. These innovative, sustainable organocatalytic processes have successfully facilitated the conversion of raw starting materials into valuable compounds, including sulfur(VI) fluoride exchange (SuFEx) click hubs and tetrasubstituted carbon centers incorporating heteroatoms.1 Introduction2 Water-Accelerated N-Heterocyclic Carbene (NHC) Catalysis for β-Aminosulfonyl Fluorides3 Water-Accelerated Phosphazene Superbase Catalysis for β-Sulfidosulfonyl Fluorides and γ-Geminal Dithioester-Incorporated Sulfonyl Fluorides4 Water-Accelerated Synergistic Superacid Catalysis for α-Tertiary Amines5 Solvent-, Metal-, and Purification-Free PPM (parts per million) Neutral Organic Salt Catalysis for Tertiary Cyanohydrin Derivatives6 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-07-19T10:26:28+01:00
  DOI: 10.1055/a-2106-1585
Direct Fluoroalkylthiolation Based on Fluoroalkanesulfite Derivatives
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  Authors: Wei; Jingjing, Liang, Shuaishuai, Jiang, Lvqi, Yi, Wenbin
  Pages: Abstract: Fluoroalkylthio groups have received substantial attention in the past decade because of their unique physicochemical characteristics, and methods for incorporating these substituents into organic molecules have been rapidly developed in recent years. This account summarizes our efforts on the development of direct fluoroalkylthiolation with fluoroalkanesulfite derivatives. Several innovative and efficient strategies for the fluoroalkylthiolation of various substrates are disclosed, leading to various valuable fluoroalkylthiolated compounds in good yields.1 Introduction2 Fluoroalkylthiolation with Sodium Fluoroalkanesulfinate3 Fluoroalkylthiolation with Fluoroalkanesulfonyl Chloride4 Fluoroalkylthiolation with Other Fluoroalkanesulfite Derivatives5 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-07-17T08:31:08+01:00
  DOI: 10.1055/a-2103-9823
Recent Advances in the Synthesis of 5-(Hetero)aryl Uracil Derivatives
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  Authors: Wang; Zhao-Li, Liu, An-Di, Liu, Li, Cheng, Liang
  Pages: Abstract: C5-Aryl/heteroaryl uracil-based compounds have attracted continuous interest because of their wide biological potential. In this review, we outline the primary synthetic methods used to prepare designated uracils, various combinations of which have been used to synthesize target compounds with potential biological activities. The significance of each approach and its limitations are also summarized.1 Introduction2 Coupling of Prefunctionalized Uracils with (Hetero)aryl Reagents2.1 Negishi Coupling2.2 Suzuki–Miyaura Coupling2.3 Stille Coupling3 Coupling of Functionalized Uracils with Nonactivated Aromatic (Hetero)cycles3.1 Photochemically Induced Coupling3.2 Palladium-Catalyzed Coupling4 Coupling of Nonactivated Uracil/Uridine with Functionalized Aromatic (Hetero)cycles4.1 Electrochemical Reduction4.2 Transition-Metal-Catalyzed Coupling4.3 Light-Promoted Coupling of Uracils with Diazonium Salts5 Direct Coupling of Nonactivated Uracils with Nonactivated Aromatic (Hetero)cycles6 Summary and Prospects
  Citation: Synlett ; : -
  PubDate: 2023-07-14T10:15:25+01:00
  DOI: 10.1055/a-2091-1071
Nickel/Photoredox-Catalyzed Decarboxylative Coupling of Aryl Bromides with
N-Protected Glycine as an Aminomethyl Source
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  Authors: Jung; Jaehyun, Kinoshita, Takumi, Makihara, Yuta, Sakakibara, Yota, Amaike, Kazuma, Murakami, Kei, Itami, Kenichiro
  Abstract: Benzylamines are important scaffolds that are ubiquitously found in various bioactive molecules. Among the benzylamine derivatives, primary benzylamines (ArCH2NH2) are regarded as valuable building blocks for pharmaceuticals. Herein, we report decarboxylative aminomethylation of aryl bromides with N-protected glycine under nickel/photoredox-catalyzed conditions. The corresponding products can be easily deprotected under acidic conditions to give primary benzylamines.
  Citation: Synlett ; : -
  PubDate: 2023-07-13T11:43:04+01:00
  DOI: 10.1055/s-0041-1738444
Synthesis of Ynamides by C(sp)–H Amidation
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  Authors: Xie; Xiaolan, Hou, Na, Lin, Yan, Lei, Jian
  Abstract: Ynamides are versatile reactive building blocks in organic chemistry; consequently, synthetic methodologies to fabricate these compounds have received extensive attention. The construction of a C–N bond between an alkyne surrogate and an amide is a powerful and practical way to access ynamides, and has been widely studied. Recently, the amidation of terminal alkynes has emerged as a straightforward alternative. This Synpacts article briefly summarizes the use of C(sp)–H amidation strategies to form ynamides; it also highlights our recent work on the synthesis of ynehydrazides through the copper-catalyzed addition of terminal alkynes to dialkyl azodicarboxylates. Finally, some future directions in this field are outlined.
  Citation: Synlett ; : -
  PubDate: 2023-07-12T10:30:01+01:00
  DOI: 10.1055/a-2103-9720
Functional α-Cyanostilbenes: Sensing to Imaging
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  Authors: Dahiwadkar; Rahul, Kaloo, Masood A., Kanvah, Sriram
  Pages: Abstract: In recent years, there has been considerable interest in cyanostilbenes due to their unique photophysical properties. The compounds emit light when aggregating, commonly called aggregation-induced emission (AIE). This remarkable feature makes cyanostilbenes ideal for various sensing applications, especially in aqueous environments. The detection of various analytes, such as metal ions and nitroaromatic compounds, has been accomplished using these compounds through various sensing mechanisms from chelation-enhanced fluorescence to fluorescence quenching. Furthermore, cyanostilbenes have shown great promise in biological imaging applications and have been employed for intracellular imaging, tracking, and targeting of sub-cellular organelles. The development and utilization of cyanostilbenes can significantly impact advanced sensing and imaging technologies in both analytical and biological fields. This potential stems from the unique properties of cyanostilbenes, such as their AIE characteristics, which sets them apart from other compounds and makes them highly useful for various applications. Further exploration and development of cyanostilbenes could lead to the creation of novel sensing and imaging technologies with wide-ranging applications in both academic and industrial settings.
  Citation: Synlett ; : -
  PubDate: 2023-07-11T10:09:16+01:00
  DOI: 10.1055/a-2091-0916
Toward the Total Synthesis of Schinortriterpenoids: Construction of the
All-cis-Substituted Cyclopropane Unit
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  Authors: Yagita; Ryotaro, Irie, Kazuhiro, Tsukano, Chihiro
  Pages: Abstract: As a step toward a total synthesis of pre-schisanartanins and arisanlactones, we successfully synthesized a right fragment of Schisandra nortriterpenoids bearing a distorting all-cis-substituted cyclopropane from a chiral lactone. The key step in this synthesis was the diastereoselective construction of an all-cis-substituted cyclopropane through a Negishi coupling using an amide as a directing group.
  Citation: Synlett ; : -
  PubDate: 2023-07-10T13:01:02+01:00
  DOI: 10.1055/a-2102-8014
Pt(II)-Bisacetylide ‘Roller Wheels’: Molecular Engineering towards
Small Bandgap, High Crystallinity, and Controlled Triplet Exciton
Processes
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  Authors: Qin; Yang
  Pages: Abstract: Triplet excitons are ubiquitous in organic chromophores and possess intrinsically longer lifetimes than their singlet exciton counterparts, and thus potentially larger diffusion lengths that have been considered beneficial for organic solar cells (OSCs). However, existing triplet-generating materials rarely possess low bandgap, high triplet energy and yield, and good crystallinity and charge mobility within a single compound. In this Account, I first describe the rationales behind our ‘roller-wheel’-type molecular structural designs through a brief literature survey and our initial attempt in Pt-containing conjugated polymers. Then, a series of novel Pt-bisacetylide-containing small molecules will be discussed. I mainly focus on the thought process for selecting the building blocks and detail their synthetic strategies, as well as their solid-state structures, especially that of the single crystals, confirming the effectiveness of our structural designs. Next, photophysical properties of these compounds are discussed in the context of optical spectroscopy and transient absorption spectroscopy, which is corroborated by theoretical calculations. Organic solar cells employing these compounds are introduced next, one of which displayed record-setting performance among Pt-containing materials. I end this Account with an outlook on future works with a focus on molecular engineering to control triplet excited-state energetics and dynamics.1 Introduction2 Initial Attempt3 Rationale of Design4 Synthesis of ‘Roller Wheels’5 Solid-State Structures of ‘Roller Wheels’6 Photophysical Studies7 Theoretical Investigation8 Device Application9 Outlook – Managing Triplet Excited States
  Citation: Synlett ; : -
  PubDate: 2023-07-06T15:07:22+01:00
  DOI: 10.1055/a-2095-5164
Novel Zinc(II) Phthalocyanine Dyes for Color Photoresists
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  Authors: Wang; Wanying, Yao, Qichao, Xu, Runfeng, Wang, Ankang, Chen, Pengzhong, Peng, Xiaojun
  Abstract: Color photoresists are the key materials for the fabrication of color filters (CFs). Organic dyes offer a promising alternative to the conventional pigment-based system to make CFs with higher resolution. However, the stability of dye molecules is an urgent problem to be solved. Herein, we designed and synthesized a series of highly stable zinc phthalocyanine dyes containing polymerizable acrylamide groups. Upon light exposure, dense and insoluble network structures were formed in the prepared CFs, which increase the thermal stability and anti-migration capacity of these dyes.
  Citation: Synlett ; : -
  PubDate: 2023-06-26T09:43:06+01:00
  DOI: 10.1055/a-2082-0818
Bromamine-T (TsNBrNa): A Biologically Significant, Versatile Bromo-Organic
Reagent
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  Authors: Kashyap; Sauvik, Phukan, Prodeep
  Abstract: Bromamine-T (BAT) is a notable member of a special class of compounds called organic haloamines, which are oxidising agents. It can act as the source of halonium ions, hypohalite species, and N-anions, whilst also displaying basic and nucleophilic properties. Bromamine-T finds wide application as an efficient reagent for various organic transformations, such as aminobromination, amination, oxidation, and others. It can be used under mild conditions and has low toxicity. Moreover, due to its immense biological significance, this reagent is piquing the interest of many researchers.1 Introduction1.1 The Sodium Salt of N-Bromo-p-toluenesulfonamide (Bromamine-T or TsNBrNa): Reagent Overview1.2 Physical Properties of Bromamine-T1.3 Preparation and Characterisation of Bromamine-T2 Biological Significance of Bromamine-T3 Organic Transformations Using Bromamine-T3.1 Aminobromination3.2 Amination3.3 Aminohydroxylation3.4 Aziridination3.5 Bromination3.6 Oxidation: Kinetic and Mechanistic Studies4 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-06-23T10:21:34+01:00
  DOI: 10.1055/a-2089-4821
Comparison of Diastereoselective ortho-Metalations and C–H Activations
of Chiral Ferrocenes
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  Authors: Čarný; Tomáš, Šebesta, Radovan
  Abstract: Chiral ferrocene derivatives possessing a planar stereogenic unit are important as chiral catalysts and materials. The principle method to obtain 1,2-disubstituted planarly chiral ferrocenes is base-mediated ortho-metalation performed on a chiral ferrocene derivative, typically using organolithium bases. A multitude of chiral ligands and other useful compounds have been synthesized by using this methodology. Newer methodologies employing transition-metal-catalyzed C–H bond activation strategies complement ortho-metalation methods and affords access to different types of planar chiral ferrocene derivatives.1 Introduction2 Base-Mediated ortho-Deprotonations3 Diastereoselective C–H Activations4 Examples of Enantioselective C–H Activations5 Conclusions
  Citation: Synlett ; : -
  PubDate: 2023-06-16T10:29:36+01:00
  DOI: 10.1055/a-2089-4934
Synthesis of an Azo-Cyanine Dye as an RNA Probe for Distinguishing
Gram-Positive Bacteria from Gram-Negative Bacteria
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  Authors: Wu; Ruixin, Li, Zipeng, Xia, Tianping, Cai, Wenlin, Du, Jianjun, Fan, Jiangli, Peng, Xiaojun
  Abstract: We have developed a new cyanine fluorescent probe, Azo-ETO3, that shows better RNA selectivity than commercial dyes in solution. Azo-ETO3 can image the RNA of mitochondria in living cells and the RNA of the nucleolus and cytoplasm in fixed cells. As a practical application, Azo-ETO3 emits strong fluorescence when interacting with Gram-positive bacteria, and it can be used to selectively label G+ bacteria in the presence of other bacteria. In addition, Azo-ETO3 exhibits low toxicity and has essentially no major impact on bacterial colony growth. These properties could make it useful as a tool for distinguishing bacterial species.
  Citation: Synlett ; : -
  PubDate: 2023-06-12T11:36:28+01:00
  DOI: 10.1055/s-0042-1751462
Continuous-Flow Synthesis of Cyclobutenes Using LED Technology
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  Authors: Smyth; Megan, Moody, Thomas S., Wharry, Scott, Baumann, Marcus
  Abstract: Cyclobutenes are highly strained ring systems of considerable synthetic interest that can be accessed via cycloaddition reactions between alkenes and alkynes. However, their traditional preparation relies on photochemical [2+2] cycloadditions that exploit low-wavelength UV radiation emitted from inefficient medium-pressure Hg lamps. This paper reports on the development of a modern approach using a high-power LED set-up emitting at the boundary of UV-A and visible light in conjunction with a continuous-flow reactor. The resulting flow process renders a series of cyclobutenes from maleimides and various commercial alkynes. This provides a more energy-efficient approach that is readily scalable to access multigram quantities of cyclobutenes in high chemical yields and short residence times. The value of these products is exemplified by flow-based hydrogenations yielding highly substituted cyclobutanes which represent sought after building blocks in modern medicinal chemistry programs.
  Citation: Synlett ; : -
  PubDate: 2023-06-06T10:54:05+01:00
  DOI: 10.1055/a-2086-0630
Synthesis of Heavy-Atom-Free Triplet Photosensitizers Based on Organoboron
Complexes
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  Authors: Koli; Mrunesh, Mula, Soumyaditya
  Abstract: A new class of organoboron complexes have been developed as heavy-atom-free triplet photosensitizers. A methodology was developed for the synthesis of an indolocarbazole–imine boron diﬂuoride (IIBD) dye and its dimer from a 6-formylindolocarbazole. The IIBD dye was then coupled with a BODIPY dye through the C-2 or C-8 position of the latter to synthesize two dyads. Both dyads showed superior photophysical properties to those of the IIBD dyes. The relative triplet conversion efficiencies of these dyes were determined by measuring their singlet-oxygen (1O2) generation capacities. All the synthesized dyes showed high 1O2 generation compared with the BODIPY dye PM567. The dyad linked through the C-2 position of the BODIPY core showed the highest 1O2 generation efficiency, which could be useful for photodynamic therapy of cancers.
  Citation: Synlett ; : -
  PubDate: 2023-06-05T14:51:51+01:00
  DOI: 10.1055/a-2086-0530
Palladium-Catalyzed Acylation Strategies and Their Applications Towards
Biologically Relevant Products
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  Authors: Sreenivasulu; Chinnabattigalla, Kishore, Dakoju Ravi, Basuli, Suchand, Satyanarayana, Gedu
  Abstract: Ketones are fundamental synthons in organic synthesis due to their wide range of applications, which include natural products, pharmaceuticals, dyes, fragrances, agrochemicals, and electronic materials. In recent years, direct acylation strategies based on commercially available benchtop aryl halides and aldehydes (alkyl/aryl) have been the prime focus for the construction of alkyl-aryl/aryl-aryl ketones using palladium catalysis under eco-friendly reaction conditions. In this account, we present conceptually developed palladium-catalyzed direct acylation strategies for achieving various carbo- and heterocycles such as ketones, 2-quinolinones, phthalazines, phthalazinones, benzoxazinones, anthraquinones, indenones, and 1,3-dihydroisobenzofurans. Significantly, these direct acylation strategies have been extended to synthesize the natural product neo-lignan and biologically significant molecules such as an n-butylphthalide antiplatelet drug, pitofenone, fenofibrate, a HBV inhibitor, and a PDE-4 inhibitor. This Account will be of interest to synthetic organic chemists wishing to prepare pharmaceutical molecules and natural products.1 Introduction2 Discussion2.1 Palladium-Catalyzed Environmentally Compassionate Acylation2.2 Palladium-Catalyzed Acylations Followed by Intramolecular Aldol Condensation to Afford Indenones2.3 Acylation of Iodo-acetanilides/Iodo-phenyl Acetates: Sequential One-Pot Syntheses of 2-Quinolinones2.4 A One-Pot Diversified Synthesis of Phthalazines, Phthalazinones, and Benzoxazinones2.5 Palladium-Catalyzed Direct Acylation: A One-Pot Relay Synthesis of Anthraquinones2.6 Palladium-Catalyzed Direct Oxidative Coupling of Primary Alcohols with Iodoarenes Leading to Ketones: Application to the Synthesis of Benzofuranones and Indenones3 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-06-05T12:26:17+01:00
  DOI: 10.1055/s-0042-1751461
Borylative Difunctionalization of Unsaturated Hydrocarbons Using
Borylcopper Species
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  Authors: Fujihara; Tetsuaki
  Abstract: This account summarizes the Cu-catalyzed borylative functionalizations of unsaturated hydrocarbons that we have developed over the past decade. First, we focus on the regioselective hydroboration of unsymmetrical internal alkynes and 1,2-dienes. Secondly, a borylative allyl–allyl coupling using 1,2-dienes, B2pin2, and an allyl phosphate is presented. Thirdly, we introduce the boroacylation and boroformylation of 1,2-dienes by using an acid anhydride or formate, respectively, as the electrophile. Lastly, we describe the synthesis of 2-boryl-1,3-butadienes and cyclic allylborates. These reactions offer a versatile method for synthesizing a broad range of useful compounds and also provide a detailed understanding of the reaction mechanism, which could lead to the development of catalysts that are both more efficient and more selective.1 Introduction2 Hydroboration of Alkynes3 Hydroboration of 1,2-Dienes and 1,3-Dienes4 Synthesis of 2-Boryl-1,3-butadienes5 Boroallylation of 1,2-Dienes6 Boroacylation of 1,2-Dienes7 Boroformylation of 1,2-Dienes and 1,3-Dienes8 Synthesis of Cyclic Allylborates9 Conclusion and Outlook
  Citation: Synlett ; : -
  PubDate: 2023-06-05T09:54:16+01:00
  DOI: 10.1055/a-2081-8907
Near-Infrared Hemicyanine Fluorophores with Optically Tunable Groups: A
‘Leap Forward’ for in Vivo Sensing and Imaging
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  Authors: Huang; Jing, He, Long, Wang, Jiaoliang, Xu, Junchao, Yuan, Lin
  Abstract: Hemicyanine dyes, with a tunable optical site and high wavelength tailorability, are of significant importance in the fields of sensing and diagnosis. Following the discovery of the near-infrared (NIR) (650–900 nm) fluorescent dyes Changsha (CS) and Huda (HD) by our group, remarkable progress has been made in the development of hemicyanine-based probes for in vivo imaging and detecting. In this review, we summarize the key contributions made by our group in developing long-wavelength (650–1700 nm) hemicyanines and utilizing them to construct functional probes. Finally, potential drawbacks and future prospects of hemicyanine dyes/probes are discussed.1 Introduction2 Changsha (CS) Dyes3 Huda (HD) Dyes4 Construction of Hemicyanine Fluorophores in the NIR-II Region5 Summary and Outlook
  Citation: Synlett ; : -
  PubDate: 2023-06-01T10:05:47+01:00
  DOI: 10.1055/a-2071-4549
Enantioselective Formal Synthesis of (–)-Catharanthine through
Enzyme-Catalyzed Desymmetrization of a meso-Azabicyclo [2.2.2]octane
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  Authors: Ikeda; Kotaro, Harada, Shingo, Hashimoto, Yoshinori, Homma, Haruka, Kono, Masato, Zumbrägel, Nadine, Gröger, Harald, Nemoto, Tetsuhiro
  Abstract: Iboga-type indole alkaloids are a promising compound group of potentially effective drugs. The common indole-fused pentacyclic skeleton is composed of an isoquinuclidine, and both enantiomers of this architecture are naturally present. In this study, we used enzymatic desymmetrization to obtain an optically active isoquinuclidine possessing four chiral carbon centers from a prochiral diester in one step. In addition, we synthesized a pentacyclic intermediate for catharanthine in an enantioenriched form through the late-stage construction of the common Iboga scaffold.
  Citation: Synlett ; : -
  PubDate: 2023-05-31T08:31:49+01:00
  DOI: 10.1055/a-2086-0690
Chemical Diversification of Carbocyclic Fluorinated Pyrimidine
Nucleosides: Introducing 2′-Arabino Analogues and Ring Unsaturation
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  Authors: Benckendorff; Caecilie M. M., Hawes, Chris S., Smith, Mark, Miller, Gavin J.
  Abstract: Analogues of the canonical nucleosides have a longstanding presence and proven capability within medicinal chemistry and drug-discovery research. Herein, we report chemical diversification of carbocyclic pyrimidine nucleosides containing CF2 and CHF in place of the furanose oxygen to introduce ring unsaturation and 2′-epimers. Utilizing gram-scale access to 6′-(R)-monofluoro- and 6′-gem-difluorouridine, we explore the provision of 2′,3′-didehydro-2′,3′-dideoxy, and 1′,2′-didehydro-2′-deoxy analogues, alongside the first example of a 6′-(R)-fluoro arabino-carbauridine. Key stereochemistries and the presence of unsaturation are confirmed using X-ray crystallography and NMR, and an indicative conformational preference for a monofluoro 2′,3′-didehydro-2′,3′-dideoxy system is presented. This synthetic blueprint offers a potential to explore biological activity for these hitherto unavailable materials, including a direct comparison to established nucleoside analogue drugs.
  Citation: Synlett ; : -
  PubDate: 2023-05-31T08:03:57+01:00
  DOI: 10.1055/a-2079-9310
Synthesis of a Heavy-Atom-Free BODIPY and its Photooxygenation of
1-Naphthol to 1,4-Naphthoquinone
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  Authors: Zhou; Meizhu, Hu, Xinhu, Zhang, Dongxiang, Cui, Tianfang, Jiang, Xin-Dong
  Abstract: By using 1,5,6,7-dihydro-4H-indol-4-one, a carbonyl group was introduced onto a BODIPY photosensitizer. The resulting heavy-atom-free BODIPY is a highly effective producer of singlet oxygen with a calculated quantum yield (ΦΔ) of 0.68, compared with that of methylene blue (ΦΔ = 0.57). Photooxygenation of 1-naphthol to 1,4-naphthoquinone was achieved by using this heavy-atom-free BODIPY catalyst in the presence of white-light irradiation under air atmosphere. Our work demonstrated a practical example of the design of a heavy-atom-free BODIPY, capable of efficient singlet-oxygen generation, with a potential in photocatalysis.
  Citation: Synlett ; : -
  PubDate: 2023-05-26T08:10:33+01:00
  DOI: 10.1055/a-2082-0688
Palladium-Catalyzed Cyanation of Nucleobases: Total Synthesis of
Toyocamycin, Sangivamycin, and a Mycalisine A Precursor
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  Authors: Shet; Harshita, Sahu, Rajesh, Sanghvi, Yogesh S., Kapdi, Anant R.
  Abstract: Installation of cyano group functionality onto nucleosides has always been a challenging task for chemists, and catalytic protocols developed for simple aryl substrates have, in most cases, failed to replicate their success when applied to nucleobase or sugar moieties of nucleosides. Given the importance of the cyano and amide functionalities in nucleoside chemistry, we herein disclose an efficient Pd-catalyzed cyanation protocol specifically applied to iodo nucleobases. Furthermore, the developed cyanation method has been explored for the synthesis of naturally occurring and bioactive nucleosides such as toyocamycin, sangivamycin, and a mycalisine A precursor.
  Citation: Synlett ; : -
  PubDate: 2023-05-25T09:50:41+01:00
  DOI: 10.1055/a-2079-9411
Acyclic 2-Ethynylnaphthalene-Modified
8-Aza-3,7-dideaza-2′-deoxyadenosine Allows Thymine Discrimination by
Probing the DNA Minor Groove Environment
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  Authors: Oku; Yurino, Kai, Misaki, Kobayashi, Saika, Katoh, Ryuzi, Saito, Yoshio
  Abstract: Two novel acyclic environment-sensitive fluorescent nucleosides named ac37zA and an37zA are synthesized and their photophysical properties are investigated. Both ac37zA and an37zA exhibit dual fluorescence emission depending upon molecular coplanarity. Oligodeoxynucleotide probes containing ac37zA clearly discriminate perfectly matched thymine in target DNA strands by strong charge transfer (CT) emission in the longer wavelength region and by strong quenching of emission from the twisted conformation in the mismatched case.
  Citation: Synlett ; : -
  PubDate: 2023-05-23T08:09:06+01:00
  DOI: 10.1055/a-2071-7168
Anthraquinone-Catalyzed Photooxidation of Boronic Acids in a Bio-Based
Solvent (2-Me-THF)
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  Authors: Gkizis; Petros L., Serviou, Stamatis K., Balaskas, Angelos, Constantinou, Constantinos T., Triandafillidi, Ierasia, Kokotos, Christoforos G.
  Abstract: The phenol moiety appears in a wide variety of natural products, exhibiting biological activity, and in numerous active pharmaceutical compounds. Boronic acids are potential precursors of the phenol scaffold, and a plethora of efforts has been focused in developing novel and green protocols, targeting their chemoselective transformation into phenols. Photochemistry is a rapidly expanding research field converting light energy into chemical potential. Photochemical aerobic processes possess additional advantages to photochemistry and may find applications in chemical industries. Herein, a low-catalyst-loading anthraquinone-catalyzed photochemical process is demonstrated, under CFL lamp irradiation, while exploiting 2-Me-THF as the reaction medium for the conversion of boronic acids into phenols. Furthermore, a broad substrate scope was employed.
  Citation: Synlett ; : -
  PubDate: 2023-05-15T13:07:05+01:00
  DOI: 10.1055/a-2071-7077
Practical and Scalable Total Syntheses of (+)-Dysidavarones A–C
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  Authors: Kuang; Yang, Chang, Le, Wang, Bingjian, Kang, Jingyi, Chong, Chuanke, Lu, Zhaoyong
  Abstract: A practical and scalable enantioselective total syntheses of the marine anticancer sesquiterpene quinone meroterpenoids (+)-dysidavarones A–C has been accomplished. The central bridged bicyclo[3.3.1]nonane structure of dysidavarones was efficiently established by a one-pot intermolecular diastereoselective alkylation and intramolecular α-arylation of a Wieland–Miescher ketone derivative with a substituted benzylic bromide, without protection of the more-reactive C(4) carbonyl group. (+)-Dysidavarones A and ‘E’ were prepared on a 150-mg scale, demonstrating the efficiency and reliability of our synthetic route and providing sufficient amounts of the dysidavarones for further bioactivity evaluation.
  Citation: Synlett ; : -
  PubDate: 2023-05-09T10:41:17+01:00
  DOI: 10.1055/a-2066-0860
Embracing the Imperfectness of Nature using Highly Reactive N-Acyl
Azahexatrienes
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  Authors: Zheng; Kuan, Zhang, Bingbing, Hong, Ran
  Abstract: Incredible examples of controlling highly reactive functional groups to synthesize amazing architectures can be found in nature. N-Acyl azahexatriene, which is involved in biosynthesis, is clearly among them, despite the extremely limited number of examples disclosed in the literature. We explored the biomimetic synthesis of macrocarbocyclic natural products, chejuenolides A–C, as well as structural variants, to unveil the hidden stereochemical relationships between their biosynthesis and those of lankacidin antibiotics. This revealed the logic of the reaction pattern, which was likely influenced by catalytic promiscuity in nature.
  Citation: Synlett ; : -
  PubDate: 2023-05-05T08:58:55+01:00
  DOI: 10.1055/a-2066-1227
Synthetic Studies Toward Daphnezomines A and B
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  Authors: Dou; Chenguang, Yang, Ming
  Abstract: Synthetic studies toward daphnezomines A and B, members of Daphniphyllum alkaloid group with a rare azaadamantane core structure, are reported. The tricyclic carbon skeleton with two contiguous quaternary carbon centers was synthesized in nine steps from (R)-piperitone. An intramolecular Tsuji–Trost reaction was used as a key reaction for the assembly of the skeleton.
  Citation: Synlett ; : -
  PubDate: 2023-05-04T07:59:03+01:00
  DOI: 10.1055/s-0041-1738436
Collective Total Synthesis of β-Carboline-Type Monoterpenoid Indole
Alkaloid Glycosides
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  Authors: Sakamoto; Jukiya, Hiruma, Daiki, Kitajima, Mariko, Ishikawa, Hayato
  Abstract: The collective and efficient asymmetric total syntheses of five β-carboline-type monoterpenoid indole alkaloid glycosides were achieved in fewer than thirteen steps. A Pictet–Spengler reaction with α-cyanotryptamine followed by the removal of the cyano group and autoxidation (aromatization) efficiently constructed the β-carboline motif. In addition, bioinspired reactions were developed to provide different alkaloid skeletons.
  Citation: Synlett ; : -
  PubDate: 2023-04-18T09:33:17+01:00
  DOI: 10.1055/a-2053-1629
Synthesis of 2,2′-Bipyridines via Dehydrogenative Dimerization of
Pyridines Using Sodium Dispersion
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  Authors: De; Pinaki Bhusan, Ilies, Laurean, Takai, Kazuhiko, Asako, Sobi
  Abstract: 2,2′-Bipyridine derivatives were synthesized by dehydrogenative dimerization of nonactivated pyridines using sodium dispersion. The reaction features operational simplicity, mild conditions, and the use of earth abundant and nontoxic sodium as the sole metal source. Importantly, transition metals are not required, which is beneficial in the fields of materials science and drug synthesis, where the contamination of the transition metals may cause significant problems.
  Citation: Synlett ; : -
  PubDate: 2023-04-17T12:44:40+01:00
  DOI: 10.1055/a-2047-8355
Regioselective anti-Silyllithiation of Propargylic Amines
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  Authors: Sato; Tomohiko, Karad, Somnath N., Shimokawa, Jun, Yorimitsu, Hideki
  Abstract: The regioselective anti-silyllithiation of propargylic amines is developed to facilitate the efficient synthesis of alkenylsilanes. This reaction generates an alkenyllithium intermediate that is stabilized by the formation of a five-membered cyclic structure through intramolecular coordination of the nitrogen functional group. Upon subsequent treatment with an electrophile, the alkenyllithium intermediate is further functionalized to afford tetrasubstituted allylic amines bearing a β-silicon substituent.
  Citation: Synlett ; : -
  PubDate: 2023-04-12T08:05:43+01:00
  DOI: 10.1055/a-2047-8456
Total Synthesis of 4α-Hydroxyallosecurinine and Securingine F, Securinega
Alkaloids with a C4-Hydroxy Handle for Biofunctional Derivatizations
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  Authors: Park; Sangbin, Kim, Doyoung, Yang, Wooil, Han, Sunkyu
  Abstract: We describe the first total synthesis of the C4-hydroxylated securinega alkaloids 4α-hydroxyallosecurinine and securingine F. The synthetic route features an Ellman’s light-mediated hydrogen-atom-transfer-based epimerization reaction that effectively sets the desired configuration at the C2 position. Simultaneous skeletal rearrangement from neosecurinane to securinane frameworks and stereochemical reversal at the C4 site was achieved under Mitsunobu reaction conditions. The C4-hydroxy group is envisioned to serve as a handle for potential biofunctional derivatizations.
  Citation: Synlett ; : -
  PubDate: 2023-04-12T08:05:39+01:00
  DOI: 10.1055/a-2047-9680
Recent Advances in Highly Fluorescent Hydrazine-Inserted Pyrrole-Based
Diboron-Anchoring Fluorophores: Synthesis and Properties
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  Authors: Yu; Changjiang, Sun, Yingzhu, Jiao, Lijuan, Hao, Erhong
  Abstract: Hydrazine-inserted pyrrole-based diboron fluorophores that display strong fluorescence in either the solution or solid state are widely used in biomedicine and optoelectronic materials science. A growing demand calls for multiple strategies for generating novel fluorophores to solve problems of small Stokes shifts and poor solid-state fluorescence. By changing their frameworks, several series of novel diboron compounds have recently been developed as increasingly valuable classes of fluorophores owing to their tunable structures and outstanding spectroscopic properties, such as high fluorescence quantum yields, large Stokes shifts, high photostability, and low LUMO energy levels due to the presence of electron-deficient BF2 groups. This review mainly highlights key synthetic strategies for the fluorophores BOPHY, BOPPY, and BOAPY developed by our group, together with the superior properties of these compounds. Significant photophysical data for these fluorophores in solution and solid states are included within the scope of this review. The facile functionalization of these fluorophores permits practical structural modifications to generate novel versatile dyes with excellent chemical and photophysical properties. We believe that these fluorophores hold promise to make important contributions in a wide range of applications.1 Introduction2 BOPHY Fluorophore2.1 Discovery of BOPHY and its Fundamental Properties2.2 Synthesis and Properties of Modified BOPHY Derivatives3 BOPPY and BOPYPY Fluorophores3.1 Discovery of BOPPY and BOPYPY, and Their Fundamental Properties3.2 Synthesis and Properties of Benzo-Fused BOPPYs from Isoindoles3.3 Nucleophilic Substitution and Cross-Coupling Reactions of Halogenated BOPPYs3.4 Knoevenagel Reaction4 BOAPY and BOPAHY Fluorophores5 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-04-05T12:29:12+01:00
  DOI: 10.1055/a-2045-2369
New High-Performance Fluorescent Dye Scaffolds: Applications for
Bioimaging and Biosensing
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  Authors: Cheng; Junfeng, Lei, Zuhai
  Abstract: Fluorescence imaging in the shortwave infrared region (SWIR, 850–2500 nm) window has become an indispensable tool in biomedical research because it has weaker absorption, less light scattering, and less background fluorescence in this window. As we know, the design and synthesis of fluorescent dyes and fluorescent probes are the cores of fluorescence imaging and biosensing. Thus, their photophysical mechanisms exploring and bioanalytical applications are multidisciplinary and cutting-edge research topics. In this regard, we have been working on high-performance fluorescent dyes and fluorescent probes for years. In short, we have developed a series of bright, stable, aggregation-resistant, SWIR fluorescent dyes ECXs, based on a carbon-bridged spiro ring strategy. We also developed a series of high-performance SWIR fluorescent dyes CXs and Chrodols, which combine the structural advantages of cyanine and xanthenoid dyes. Based on these new SWIR scaffolds, we further constructed some activatable SWIR fluorescent probes with OFF-ON or ratiometric properties for biosensing in vivo. Therefore, the main line of our work is to gain an in-depth understanding of the photophysical mechanisms of fluorescent dyes, to create high-performance luminescent dyes, and to further develop fluorescent probes for bioimaging and biosensing.1 Introduction2 ECX Dyes Based on a Carbon-Bridged Spiro Ring Strategy3 Fluorescent Dyes and Fluorescent probes Combining the Structures of Cyanine and Xanthenoid Dyes3.1 CX Series Dyes3.2 A Functionalized Modified CX probe NRh3.3 CX-like Dyes with a Secondary Amino Py-23.4 Chrodol Series Dyes4 Conclusion and Future Prospects
  Citation: Synlett ; : -
  PubDate: 2023-04-05T11:08:28+01:00
  DOI: 10.1055/a-2033-8557
Photooxidative Coupling of Thiols Promoted by Bromo(trichloro)methane in a
Basic Aqueous Medium
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  Authors: Shan; Shiquan, Pang, Songhao, Qu, Yunwei, Lu, Yongna, Cheng, Xiamin, Li, Lin
  Abstract: A transition-metal- and organic-solvent-free oxidative coupling of thiols catalyzed by BrCCl3 and NaOH in an aqueous medium with oxygen as a green oxidant was established The facile and green method has a broad substrate scope in converting thiols into the corresponding disulfides with medium to excellent yields (up to 91%). This method could potentially be used to construct bioactive molecules containing disulfide bonds and to label bioactive molecules with disulfide bonds.
  Citation: Synlett ; : -
  PubDate: 2023-03-31T11:11:21+01:00
  DOI: 10.1055/s-0042-1752654
New Paradigms in Catalysis Inspired by Cytochromes P450
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  Authors: Gao; Yanqun, Cheng, Lu, Shi, Wei, Ouyang, Yuejun, Han, Wei
  Abstract: Cytochromes P450 (P450s or CYPs) are versatile biocatalysts capable of realizing a broad range of synthetically challenging reactions. The development of synthetic catalysts/catalytic systems that model enzyme functions is a goal that has long been pursued. In this account, we mainly summarize our latest advances in the field of catalysis inspired by cytochromes P450, including reductive activation strategies for highly efficient oxidations and an unusual l-cystine-derived ligand as a model of P450s for highly efficient iron-catalyzed undirected arene C–H hydroxylation. These new paradigms highlight some of the catalytic properties of P450s, such as effective late-stage functionalization of complex targets, good reactive functional group tolerance, and high catalytic efficiency and selectivity.1 Introduction2 Reductive Activation Strategies for Oxygenation3 An Fe/Cysteine-Based Ligand as a Biomimetic Model of Cytochromes P450 for Arene C–H Hydroxylation4 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-03-27T12:05:24+01:00
  DOI: 10.1055/a-2043-4479
A Novel Heterocyclic Xanthene-Analogous pH Probe for Quantitative
Monitoring of Cell Surface pH by Fluorescence Lifetime Imaging
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  Authors: Wu; Shuyao, Zhang, Xinfu, Li, Xiaoxi, Sun, Shulan, Wang, Ze Hui, Li, Dingxuan, Xiao, Yi
  Abstract: Rapidly capturing slight changes in cell surface pH is extremely important to evaluate the rapid diffusion of acidic metabolites into the extracellular environment caused by disease and physiological pH fluctuations of cells. In this work, we designed a membrane-targeted pH probe, Mem-COC18 , based on a novel heterocyclic xanthene-analogous backbone. Mem-COC18 shows specific and stable staining ability towards membrane. Importantly, the fluorescence lifetime of Mem-COC18 is highly sensitive against acidity within membrane, which is in favor of quantifying pH through fluorescence lifetime imaging. Using Mem-COC18 , we recorded pH changes of 0.61 units on the surface of human cervical cancer cells (Hela) during glycolysis. Further on, we observed a robust pH-regulating mechanism of the plasma membrane that the pH fluctuation range within membrane (5.32–6.85) is much smaller than the change in extracellular environment (4.00–8.00). Consequently, we demonstrate a pH probe for quantifying small pH fluctuations within cell membrane that merits further evaluation for biology applications.
  Citation: Synlett ; : -
  PubDate: 2023-03-14T08:12:05+0100
  DOI: 10.1055/a-2012-0232
Bioinspired Formal Synthesis of Pancracine via Selective
Hydrogenation of an Indole Derivative
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  Authors: Han; Shoule, Lou, Mingliang, Qi, Xiangbing
  Abstract: A bioinspired formal synthesis of the montanine-type Amaryllidaceae alkaloid pancracine through selective hydrogenation of a 3-arylindole derivative is disclosed. The key features of this synthesis include a hexahydroindole synthesis by a chemoselective hydrogenation of an aryl-substituted indole and a diastereoselective silyl hydride reduction of an iminium intermediate generated from an enaminone through Tf2O activation. The eight-step assembly of the 5,11-methanomorphanthridine framework represents a novel and efficient strategy that permits one of the shortest syntheses of pancracine reported so far.
  Citation: Synlett ; : -
  PubDate: 2023-02-28T09:37:55+0100
  DOI: 10.1055/a-2021-7944
Investigations on Biomimetic Dimerization in Natural Product Synthesis
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  Authors: Zhang; Fan, Chen, Chongchong, Hu, Xiangdong
  Abstract: Biomimetic dimerization is a fascinating pathway to natural product synthesis. By using structurally inferior monomers, complex molecular architectures can be readily established with distinct efficiency and elegance. In this Account, our investigation on biomimetic dimerization in natural product synthesis has been summarized, which includes our synthetic exploration of linderaspirone A, bi-linderone, parvistemin A, (±)-diperezone, scabellone B, and spiroxins A/C/D.1 Introduction2 Biomimetic Dimerization in the Synthesis of Linderaspirone A and Bi-linderone3 Biomimetic Dimerization in the Synthesis of Parvistemin A and (±)-Diperezone4 Biomimetic Dimerization in the Synthesis of Scabellone B5 Dimerization Investigation in the Synthesis of Spiroxins A/C/D6 Conclusion
  Citation: Synlett ; : -
  PubDate: 2023-02-28T09:37:47+0100
  DOI: 10.1055/a-2021-7993
Bioinspired Total Syntheses of Gymnothelignans
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  Authors: Hong; Xiaoling, Chen, Peng, Li, Huilin, She, Xuegong
  Abstract: Since 2012, Xu and Zhou have reported the isolation of a series of gymnotheligans, a large group of novel tetrahydrofuran-containing lignan natural products. In the past decade, considerable achievements in the total syntheses of these lignans have been achieved based on a plausible biogenetic pathway proposed by our group in 2014. In this account, we summarize these remarkable synthetic works of the past ten years.1 Introduction2 Biogenetic Pathways to Gymnothelignans3 Total Syntheses of Eupodienones4 Total Syntheses of Eupomatilones5 Total Synthesis of Dibenzocyclooctenes6 Conclusions
  Citation: Synlett ; : -
  PubDate: 2023-02-09T11:29:37+0100
  DOI: 10.1055/s-0042-1751416
Sequential Bromination/Dearomatization Reactions of 2-Methoxyphenols en
route to Bromo-Substituted ortho-Quinonemonoacetals
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  Authors: Hayashi; Shunya, Takasu, Kiyosei, Takikawa, Hiroshi
  Pages: Abstract: A novel method involving the sequential dibromination and dearomatization of 2-methoxyphenols with N-bromosuccinimide (NBS) is described, providing rapid access to brominated ortho-quinone monoacetals (o-QMAs). Our method demonstrates two notable aspects: (1) the introduction of a bromo group(s) into the aromatic ring and its subsequent conversion into o-QMAs in a single operation, and (2) the use of NBS as a convenient oxidant in oxidative dearomatization reactions.
  Citation: Synlett ; : -
  PubDate: 2023-08-11T10:07:46+01:00
  DOI: 10.1055/s-0041-1738450
  Issue No: Vol. eFirst

Synthesis and Coordination Behavior of 9,10-Diarsatriptycene

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Authors: Inaba; Ryoto, Kikuchi, Takashi, Imoto, Hiroaki, Naka, Kensuke
Pages: Abstract: Herein, 9,10-diheterotriptycenes (DHTs) containing heavy pnictogens (Pn, Pn = As, Sb, and Bi) are synthesized without using the dangerous chemicals used in conventional synthetic methods: tert-butyllithium, organomercury reagents, or trichloroarsine. In particular, 9,10-diarsatriptycene is obtained in relatively high yield and is stable under oxidation and coordination reactions. Additionally, the gold chloride complex 9,10-diarsatriptycene forms a one-dimensional supramolecular polymer constructed through coordination and aurophilic interactions.
Citation: Synlett ; : -
PubDate: 2023-08-10T09:57:34+01:00
DOI: 10.1055/a-2112-9605
Issue No: Vol. eFirst

A Practical Synthesis of Near-Infrared Benzannulated Xanthenoid Dyes

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Authors: Li; Jin, Wei, Ruwei, Zhang, Xiaodong, Luo, Xiao, Qian, Xuhong, Yang, Youjun
Pages: Abstract: Near-infrared dyes are sought after for their potential in biomedical applications. Benzoxanthene dyes with a non-oxygen bridging atom are expected to exhibit longer absorption and emission wavelengths than their oxygen-containing counterparts, yet their synthesis remains unaddressed. Herein, we report the first syntheses of non-oxygen-bridged benzoxanthenes starting from a 7-bromo-2-aminonaphthalene derivative, and discuss their photophysical properties as well as their potential for in vivo imaging.
Citation: Synlett ; : -
PubDate: 2023-08-07T12:01:23+01:00
DOI: 10.1055/s-0042-1752719
Issue No: Vol. eFirst