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Scientific Reports     Open Access   (Followers: 85)
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Wiley Interdisciplinary Reviews : Computational Molecular Science     Hybrid Journal   (Followers: 4)
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Synthesis
Journal Prestige (SJR): 0.974
Citation Impact (citeScore): 2
Number of Followers: 56  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0039-7881 - ISSN (Online) 1437-210X
Published by Thieme Publishing Group Homepage  [233 journals]
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      Synthesis 2022; 54: V-
      DOI: 10.1055/s-0041-1737606



      Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

      Artikel in Thieme eJournals:
      Inhaltsverzeichnis

      Synthesis 2022; 54: V-2022-05-16T00:00:00+01:00
      Issue No: Vol. 54, No. 11 (2022)
       
  • SYNFORM ISSUE 2022/4

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      Synthesis 2022; 54: A81-A100
      DOI: 10.1055/s-0040-1720563



      Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

      Artikel in Thieme eJournals:
      Inhaltsverzeichnis

      Synthesis 2022; 54: A81-A1002022-05-16T00:00:00+01:00
      Issue No: Vol. 54, No. 11 (2022)
       
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      Synthesis 2022; 54: V-
      DOI: 10.1055/s-0041-1737592



      Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

      Artikel in Thieme eJournals:
      Inhaltsverzeichnis

      Synthesis 2022; 54: V-2022-04-27T00:00:00+01:00
      Issue No: Vol. 54, No. 10 (2022)
       
  • Recyclable Palladium-Catalyzed Carbonylative Coupling of 2-Iodoanilines,
           Trimethyl Orthoformate, and Amines: A Practical Synthesis of
           Quinazolin-4(3H)-ones

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      Authors: Li; Jianying, Zhou, Zebiao, Xie, Gang, Cai, Mingzhong
      Abstract: An efficient heterogeneous palladium-catalyzed carbonylative annulation of 2-iodoanilines, trimethyl orthoformate, and amines has been developed. The reaction proceeds smoothly in toluene at 110 °C using N,N-diisopropylethylamine (DiPEA) as base and 2 mol% of MCM-41-anchored bidentate phosphine palladium complex [MCM-41-2P-Pd(OAc)2] as catalyst under 10 bar of carbon monoxide and provides a general and practical method for the construction of a wide variety of quinazolin-4(3H)-ones in good to excellent yields from commercially easily available starting materials. This heterogenized palladium catalyst can be easily recovered via a simple centrifugation process and reused more than nine times with almost consistent catalytic efficiency.
      Citation: Synthesis ; : -
      PubDate: 2022-05-19T00:00:00+01:00
      DOI: 10.1055/s-0040-1719924
       
  • Telescoped Continuous Flow Synthesis of 2-Substituted 1,4-Benzoquinones
           via Oxidative Dearomatisation of para-Substituted Phenols Using Singlet
           Oxygen in Supercritical CO2

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      Authors: Abreu; Bruna L., Boufroura, Hamza, Moore, Jonathan C., Poliakoff, Martyn, George, Michael W.
      Abstract: This paper describes a continuous multi-step synthesis in supercritical CO2. A continuous flow synthesis of 2-substituted 1,4-benzoquinones is reported, and details of the high-pressure reactors are given. This proceeds via the telescoped dearomatisation of p-substituted phenols using singlet oxygen in supercritical CO2 and an acid-mediated C–C migration. The process has a short residence time of 30 minutes, with overall yields and projected productivities of up to 83% and 9 g/day, respectively. This methodology enables a safe and efficient synthesis of 2-substituted 1,4-benzoquinones from photo-generated singlet oxygen, and cheap and readily available p-substituted phenols. The procedure has high atom efficiency, low photocatalyst loading, and substitutes potentially hazardous and corrosive reagents and solvents for molecular oxygen, CO2, and the less hazardous solid-supported acid Amberlyst-15.
      Citation: Synthesis ; : -
      PubDate: 2022-05-12T00:00:00+01:00
      DOI: 10.1055/s-0041-1737413
       
  • Expanding the Library of 2-Phenylbenzotellurazoles: Red-Shifting Effect­
           of Ethoxy Functionalities on the UV/Vis Absorption Properties

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      Authors: Romito; Deborah, Amendolare, Leonardo, Kalathil, Krishnan K., Bonifazi, Davide
      Abstract: This work describes the high-yield synthesis of a novel series of benzotellurazoles bearing a phenyl ring in 2-position, which is differently functionalized with ethoxy chains. Changing the number and the position of these functional groups determines differences in the self-assembly in the solid state, as well as in the photophysical properties of the targeted molecules. As anticipated by theoretical calculations of the HOMO-LUMO gap of each molecule, the presence of ethoxy chains in o- and p-positions determines up to 20 nm red-shifts in the absorption peaks, when compared to unsubstituted benzotellurazole. Similarly, more significant changes are observed in the chemical shifts of 125Te NMR spectra for those derivatives bearing o- and p-ethoxy functionalization.
      Citation: Synthesis ; : -
      PubDate: 2022-05-10T00:00:00+01:00
      DOI: 10.1055/s-0041-1737898
       
  • Synthesis of Peptide N-Acylpyrroles via Anodically Generated N,O-Acetals

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      Authors: Lin; Yutong, Malins, Lara R.
      Abstract: An electrochemical approach to peptide C-terminal N-acylpyrroles is described from readily accessible C-terminal hydroxyproline-containing peptides, prepared via standard Fmoc solid-phase peptide synthesis (Fmoc-SPPS). Following electrochemical decarboxylation, the reactive hydroxyproline-derived N,O-acetal intermediate is aromatized under mild acidic conditions, which enable concomitant deprotection of amino acid side-chain protecting groups. The resulting peptide N-acylpyrrole is amenable to late-stage peptide modifications, including reduction with NaBH4 to deliver a valuable C-terminal peptide aldehyde motif.
      Citation: Synthesis ; : -
      PubDate: 2022-05-09T00:00:00+01:00
      DOI: 10.1055/s-0041-1737411
       
  • One-Pot Syntheses of Substituted 2-Aminothiazoles and 2-Aminoselenazoles
           via Meerwein Arylation of Alkyl Vinyl Ketones

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      Authors: Ostapiuk; Yurii V., Ostapiuk, Mary Y., Barabash, Oksana V., Kravets, Mykola, Herzberger, Colin, Namyslo, Jan C., Obushak, Mykola D., Schmidt, Andreas
      Abstract: Both one-pot and two-step procedures for the synthesis of substituted 2-aminothiazoles and 2-aminoselenazoles are described. Anilines are first converted into arenediazonium bromides, which are then reacted with methyl vinyl ketone or cyclopropyl vinyl ketone in the presence of copper(II) bromide to give 4-aryl-3-bromobutan-2-ones (40–71%) and 3-aryl-2-bromo-1-cyclopropylpropan-1-ones (41–79%), respectively. These products are reacted, without prior isolation, with thiourea or selenourea to prepare 4-methyl- and 4-cyclopropyl-5-(R-benzyl)thiazol-2-amines (14 examples) and their selenium analogs (14 examples). The yields of the one-pot procedure are higher (40–81%) than those of the two-step procedure (32–70%).
      Citation: Synthesis ; : -
      PubDate: 2022-05-03T00:00:00+01:00
      DOI: 10.1055/s-0041-1738070
       
  • Metal-Free Thiolation and Hydroxylation of CF3-Substituted Alkenes: A
           Practical Method to Synthesize Trifluoromethyl Tertiary Alcohols

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      Authors: Niu; Jiapan, Liu, Bowen, Zhang, Chun
      Abstract: A novel and practical method to synthesize trifluoromethyl tertiary alcohols has been developed. Under mild reaction conditions, the present reaction could be compatible with a wide range of functional groups. Moreover, the performance of gram-scale reaction and further transformations illustrated the good potential utility of the present chemistry. Furthermore, the radical process of this reaction has been proved by mechanistic studies.
      Citation: Synthesis ; : -
      PubDate: 2022-04-28T00:00:00+01:00
      DOI: 10.1055/s-0040-1719919
       
  • Selective N2-Alkylation of 1H-Indazoles and 1H-Azaindazoles

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      Authors: Clemens; Jennifer, Bell, Emily L., Londregan, Allyn T.
      Abstract: A general and selective procedure for the N2-alkylation of 1H-indazoles and 1H-azaindazoles is presented. Promoted by either trifluoromethanesulfonic acid or copper(II) triflate, diverse 1H-indazoles/azaindazoles are selectively alkylated with varied primary, secondary, and tertiary alkyl 2,2,2-trichloroacetimidates at the N2-nitrogen to afford the corresponding 2-alkyl-2H-indazoles/azaindazoles. Forty-one examples are included along with a discussion of reaction optimization, scope, and mechanism.
      Citation: Synthesis ; : -
      PubDate: 2022-04-25T00:00:00+01:00
      DOI: 10.1055/s-0040-1719917
       
  • Pyrazoles in the Intersection of Mesomeric Betaines and N-Heterocyclic
           Carbenes: Formation of NHC Selenium Adducts of Pyrazolium-4-aminides

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      Authors: Hillrichs; Kai, Namyslo, Jan C., Lederle, Felix, Hübner, Eike G., Schmidt, Andreas
      Abstract: Starting from 4-nitropyrazole, eight mesoionic pyrazolium-4-aminides were prepared by a six-step reaction sequence. The deprotonation of 1,2-disubstituted 4-amido-1H-pyrazolium salts by an anion exchange resin in its hydroxide form is the final step of the synthesis. A tautomeric equilibrium between the mesoionic compounds (pyrazolium-4-aminides) and N-heterocyclic carbenes (pyrazol-3-ylidenes) can be formulated; however, the NHC tautomers were not detected by means of NMR spectroscopy in polar aprotic solvents such as DMSO-d 6 or MeCN-d 3. Apart from tautomerism, anionic N-heterocyclic carbenes can be formulated as a result of a deprotonation of the mesoionic compounds­. Trapping reactions were performed with selenium, which resulted in the formation of pyrazole-3-selenones. Methylation at the selenium atom gave the corresponding 3-(methylselanyl)-4-amido-1H-pyrazolium salts, which were deprotonated to give new mesomeric betaines, 3-(methylselanyl)-1H-pyrazolium-4-aminides as unique compounds­. DFT-calculations as well as 77Se NMR spectroscopic measurements were carried out.
      Citation: Synthesis ; : -
      PubDate: 2022-04-20T00:00:00+01:00
      DOI: 10.1055/s-0040-1719912
       
  • External-Ligand-Free, Nickel-Catalyzed Alkenylation of N-Sulfonylamines
           with Internal Alkynes

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      Authors: Li; Jia-Yue, Li, Lun, Lin, Yun-Zhi, Shi, Hang
      Abstract: Allylic amines were synthesized via a nickel-catalyzed coupling reaction between various N-sulfonylamines and internal alkynes. The catalytic reaction was by-product-free and proceeded without the need for additional oxidant/reductant or activating reagent. As improvements over established methods, the present approach avoids the need for an external ligand, which increases the value of the approach with respect to atom economy, and it uses bench-stable Ni(II)Br2(dme) instead of Ni(0)(COD)2 as the source of the nickel catalyst. Mechanistic studies revealed that a catalytic amount of a strong base (i.e., KO t Bu) was essential for the formation of active Ni(0) catalyst, which, along with an imine intermediate, then initiated the catalytic cycle.
      Citation: Synthesis ; : -
      PubDate: 2022-04-20T00:00:00+01:00
      DOI: 10.1055/s-0040-1719913
       
  • Organic Nitrating Reagents

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      Authors: Patra; Subrata, Mosiagin, Ivan, Giri, Rahul, Katayev, Dmitry
      Abstract: Nitro compounds are vital raw chemicals that are widely used in academic laboratories and industries for the preparation of various drugs, agrochemicals, and materials. Thus, nitrating reactions are of great importance for chemists and are even taught in schools as one of the fundamental transformations in organic synthesis. Since the discovery of the first nitrating reactions in the 19th century, progress in this field has been constant. Yet, for many years the classical electrophilic nitration approach using a mixture of strong mineral acids dominated the field. However, in recent decades, the attention of researchers has focused on new reactivity and new reagents that can provide access to nitro compounds in a practical and straightforward way under mild reaction conditions. Organic nitrating reagents have played a special role in this field since they have enhanced reactivity. They also allow nitration to be carried out in an ecofriendly and sustainable manner. This review examines the development and application of organic nitrating reagents.1 Introduction2 Organic Nitrating Reagents2.1 Alkyl Nitrites2.2 Nitroalkanes2.3 Alkyl Nitrates2.4 N-Nitroamides2.5 N-Nitropyrazole2.6 N-Nitropyridinium Salts3 Organic Nitrating Reagents Generated In Situ3.1 Acyl Nitrates3.2 Trimethylsilyl Nitrate3.3 Nitro Onium Salts4 Organic Nitronium Salts5 Organic Nitrates and Nitrites5.1 Ammonium Nitrates5.2 Heteroarylium Nitrates5.3 Other Organic Nitrates5.4 Organic Nitrites6 Conclusion and Outlook
      Citation: Synthesis ; : -
      PubDate: 2022-04-13T00:00:00+01:00
      DOI: 10.1055/s-0040-1719905
       
  • Copper-Catalyzed Direct C(sp2)–H Sulfuration of Aryl Alkenes by Using
           Tetraalkylthiuram Disulfides for the Synthesis of Alkenyl Dithiocarbamates
           

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      Authors: Jiao; Jing, Zhang, Zhipeng
      Abstract: Copper-catalyzed direct C(sp2)–H sulfuration of aryl alkenes by using tetraalkylthiuram disulfides as sulfuration reagents has been developed. The reaction provides an efficient method for the synthesis of a variety of alkenyl dithiocarbamates, which are important structure motifs widely applied in materials, pharmaceuticals, and agrochemicals.
      Citation: Synthesis ; : -
      PubDate: 2022-04-07T00:00:00+01:00
      DOI: 10.1055/a-1820-2475
       
  • Rapid and Facile Synthesis of Isomaleimides: Dehydration of Maleamic Acids
           using Methanesulfonyl Chloride

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      Authors: Alam; Khyarul, McFee, Elvis C., Croatt, Mitchell P.
      Abstract: The dehydration of maleamic acids using methanesulfonyl chloride as a dehydrating agent to selectively and rapidly (
      Citation: Synthesis ; : -
      PubDate: 2022-04-07T00:00:00+01:00
      DOI: 10.1055/s-0041-1737414
       
  • Stereocontrolled Synthesis of (±)-Grandisol

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      Authors: Bartlett; William R., Read de Alaniz, Javier, Carlson, Janet L., Dillon, Maria P., Edstrom, Eric, Fischer, Derek A., Goldblum, Adam A, Luedtke, Gregory R., Paneitz, Gregory W., Ryter, Kendal, Schulz, Mark, Shepard, Donnie A., Switzer, Christopher
      Abstract: A synthetic approach to grandisol is described. The route to the cyclobutane core relies on an efficient intramolecular [2+2] cyclo­addition that establishes the required cis-ring fusion at the adjacent side chains of the cyclobutane ring. Using a new two-step lithium/halide homologation procedure, norgrandisol was efficiently converted into grandisol. This new approach enables the synthesis of grandisol in five steps from commercially available starting material in 22% overall yield.
      Citation: Synthesis ; : -
      PubDate: 2022-04-06T00:00:00+01:00
      DOI: 10.1055/s-0040-1719910
       
  • Enantiopure β3-Trifluoromethyl-β3-homoalanine Derivatives: Coupling with
           Boc-Protected Amino Acids and Conformational Studies of Peptides in Solid
           State

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      Authors: Saraiva Rosa; Nathalie, Grellepois, Fabienne
      Abstract: The use of enantiopure β3-trifluoromethyl-β3-alkyl β-amino acids for the design of peptides would contribute to drastically enhance peptide stability in vivo. Moreover, the steric hindrance generated by the substituents on the tetrasubstituted carbon adjacent to the nitrogen function coupled to the electron-withdrawing effect of the trifluoromethyl group is more likely to influence the 3D conformation of the peptide. Herein, we describe a short, scalable and robust method to synthesize N- and/or C-protected enantiopure (R)- and (S)-β3-trifluoromethyl-β3-methyl β-amino acid derivatives and liquid-phase coupling methods suitable for incorporation of Boc-protected amino acids into short α/β- and β-peptides. Conformational studies of some of these original peptides via X-ray diffraction analysis highlighted intraresidue C6 hydrogen bonds within trifluoromethylated amino acids.
      Citation: Synthesis ; : -
      PubDate: 2022-04-06T00:00:00+01:00
      DOI: 10.1055/s-0041-1737396
       
  • Potassium tert-Butoxide Facilitated Amination of Carboxylic Acids with
           N,N-Dimethylformamide

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      Authors: Huang; Yuanjing, Zhang, Jing
      Abstract: Herein a practical and efficient potassium tert-butoxide (KO t Bu)-facilitated amination of carboxylic acids with N,N-dimethylamine is described. In the presence of catalytic amount of KO t Bu, a variety of aliphatic and aromatic carboxylic acids are transformed to N,N-dimethylamides using DMF as the dimethylamine reagent with the assistance of trimethylacetic anhydride. The applicability of this protocol is demonstrated by late-stage dimethylamidation of complex drug molecules. A plausible reaction mechanism involving KO t Bu-facilitated in situ amine generation from formamide decomposition and anhydride-mediated condensation is proposed on the basis of mechanistic investigations.
      Citation: Synthesis ; : -
      PubDate: 2022-04-05T00:00:00+01:00
      DOI: 10.1055/a-1817-1965
       
  • Copper-Catalyzed C–S Formation for the Synthesis of Benzyl Phenyl
           Sulfides from Dithiocarbamates

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      Authors: Zhou; Yu, Yang, Cheng-Li, Ye, Lei, Dong, Zhi-Bing
      Abstract: An odorless and efficient protocol for the synthesis of benzyl phenyl sulfides is reported. Starting from environmentally friendly phenyl dithiocarbamates and commercially available benzyl halides as starting materials, the target compounds (benzyl phenyl sulfides) could be obtained smoothly and easily by using copper salt as catalyst and Cs2CO3 as base. This method features ligand/additive-free, the use of readily available starting materials, inexpensive catalysts, and good substrate suitability, illustrating its potentially synthetic value for the convenient preparation of some biologically active molecules.
      Citation: Synthesis ; : -
      PubDate: 2022-04-05T00:00:00+01:00
      DOI: 10.1055/a-1817-2079
       
  • Catalyst Engineering through Heterobidentate (N–X-Type) Ligand Design
           for Iridium-Catalyzed Borylation

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      Authors: Hoque; Md Emdadul, Hassan, Mirja Md Mahamudul, Haldar, Chabush, Dey, Sayan, Guria, Saikat, Chaturvedi, Jagriti, Chattopadhyay, Buddhadeb
      Abstract: Iridium-catalyzed C–H activation and borylation reactions operate under mild conditions that enable easy and atom-economical installation of the versatile boronate ester group in (het)arenes and alkanes. The standard catalytic system for iridium-catalyzed borylation uses [Ir(cod)(OMe)]2 as a precatalyst, a bipyridine type ligand, and B2pin2 or HBpin as the borylating agent. Initially, a bipyridine-ligated trisboryl–iridium complex is generated that enables the borylation reaction and the regioselectivity is mainly governed by the sterics of substituents present on the ring. As a result, monosubstituted and 1,2-disubstituted arenes give mixtures of isomers. Significant efforts by several research groups have overcome the selectivity issue for directed proximal C–H borylation by introducing a directing group and newly developed ligands. This short review aims to summarize recent elegant discoveries in directed C(sp2)–H and C(sp3)–H borylation by using heterobidentate ligand (P/N–Si, N–B, and N–C) coordinated iridium catalysts.1 Introduction2 Iridium-Catalyzed Directed C–H Borylation of C(sp2)–H Bonds3 Iridium-Catalyzed Directed C–H Borylation of C(sp3)–H Bonds4 Conclusions
      Citation: Synthesis ; : -
      PubDate: 2022-04-04T00:00:00+01:00
      DOI: 10.1055/a-1816-3334
       
  • Regiocontrol by Halogen Substituent on Arynes: Generation of 3-Haloarynes
           and Their Synthetic Reactions

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      Authors: Miyabe; Hideto
      Abstract: The use of arynes as highly reactive intermediates has attracted substantial attention in organic synthesis. To enhance the utility of arynes, the regiocontrol in the reactions of unsymmetrically substituted arynes is an important task. The introduction of halogen substituent at 3-position of arynes leads to sufficient regiocontrol for various synthetic reactions. This short review highlights the utility of 3-halo­arynes in organic synthesis and discusses the distortion models used to explain regioselectivity, representative reactions of 3-haloarynes generated from polyhaloarenes, and the preparation and reactions of easily activatable aryne precursors.1 Introduction2 Distortion Models3 Reaction of Precursors Activated by an Organometallic Reagent or Base4 Preparation of Easily Activatable Precursors5 Reactions of Easily Activatable Precursors6 Concluding Remarks
      Citation: Synthesis ; : -
      PubDate: 2022-04-01T00:00:00+01:00
      DOI: 10.1055/a-1814-9853
       
  • Synthesis and Structure–Activity Relationship Studies of Nicot­lactone
           Analogues as Anti-TMV Agents

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      Authors: He; Hong-Wei, Chi, Yuan, Chen, Cai-Yun, Wang, Fei-Yu, Wang, Jia-Xin, Xu, Dan, Zhou, Huan, Xu, Gong
      Abstract: The synthesis of the originally proposed structure of (±)-nicotlactone A, a potent antiviral lignan with three continuous chiral centers, is reported in 5 steps from methyl acrylate. The key steps of the synthesis included an In-catalyzed regioselective allylation and a Mn-catalyzed Mukaiyama hydration reaction. Our synthetic strategy also enabled us to get the other three epimers and investigate the structure–activity relationship. The NMR data of the synthesized compounds do not match that of the isolated sample, indicating that the structure of nicotlactone A remains to be reassigned. All the synthetic target compounds were evaluated for their anti-tobacco mosaic virus (anti-TMV) activity. Bioassay results indicated that (±)-8-demethylnicotlactone A displayed similar anti-TMV activity to the commercial agent ningnanmycin, thus being a promising candidate or lead compound for developing novel antiviral agents in crop protection.
      Citation: Synthesis ; : -
      PubDate: 2022-04-01T00:00:00+01:00
      DOI: 10.1055/a-1814-9637
       
  • Developments in the Alkynyltrifluoromethylations of Alkenes and Alkynes

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      Authors: Remete; Attila M., Nonn, Melinda, Volk, Balázs, Kiss, Loránd
      Abstract: As a consequence of the expanding relevance of fluorine-containing organic molecules in drug research, the synthesis of organofluorine scaffolds has high significance in synthetic organic chemistry. Trifluoromethylative difunctionalizations of carbon–carbon multiple bonds, with the simultaneous introduction of a CF3 group and another function, have considerable potential. Considering the high importance of carbon–carbon bond-forming reactions in organic synthesis, carbotrifluoromethylations and, in particular, alkynyltrifluoromethylations have increasing interest in synthetic chemistry. Alkynyltrifluoromethylation is a narrow area and a relatively new approach in synthetic chemistry­; however it has not been reviewed so far. Our goal in this short review is to summarize recent developments in alkynyltrifluoromethylation reactions by considering: (a) alkynyltrifluoromethylation reactions of alkenes, including reactions involving either intramolecular alkynyl migration or intermolecular transformation, and (b) alkynyltrifluoromethylation reactions of alkynes.1 Introduction2 Alkynyltrifluoromethylation Reactions of Alkenes2.1 Reactions Involving Intramolecular Alkynyl Migration2.2 Intermolecular Reactions3 Alkynyltrifluoromethylation Reactions of Alkynes4 Summary and Outlook
      Citation: Synthesis ; : -
      PubDate: 2022-03-30T00:00:00+01:00
      DOI: 10.1055/a-1811-8679
       
  • 1,1-Difunctionalization of α‑Carbonyl Sulfur Ylides with
           Thiosulfonates: Synthesis of β-Keto Thiosulfones

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      Authors: Kang; Xiaokang, Lai, Shuyan, Liang, Xiayu, Zeng, Qingle
      Abstract: 1,1-Difunctionalization of α‑carbonyl sulfur ylides and thiosulfonates under simple conditions is disclosed. In this protocol, two new C–S bonds are constructed in a one-step reaction. A series of aliphatic and aromatic β-keto thiosulfones were obtained in moderate to good yields. This reaction probably proceeds through sulfur ylide-involved­ nucleophilic substitution of an ion pair within a solvent cage.
      Citation: Synthesis ; : -
      PubDate: 2022-03-30T00:00:00+01:00
      DOI: 10.1055/a-1811-8503
       
  • P-Chloride-Free Synthesis of Phosphoric Esters: Microwave-Assisted
           Esterification of Alkyl- and Dialkyl Phosphoric Ester-Acids Obtained from
           Phosphorus Pentoxide

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      Authors: Harsági; Nikoletta, Kiss, Nóra Zsuzsa, Keglevich, György
      Abstract: It is a reasonable endeavour to replace P-chloride starting materials (e.g., POCl3) with greener and cheaper reagents. Our purpose was to start from phosphorus pentoxide, i.e. to utilize its reaction with alcohols in the preparation of (HO)2P(O)(OR) and HOP(O)(OR)2, and to convert the mixtures of the corresponding monoester and diester, so obtained, into the target trialkyl esters. Separate experiments showed that the monobutylphosphate undergo microwave (MW)-assisted esterification with butanol in the presence of [bmim][BF4] catalyst at 200 °C to afford dibutylphosphate in a selective manner (ca. 95%) that, in turn, may be converted into tributylphosphate by alkylation under MW irradiation. In this way, the mixtures of (HO)2P(O)(OR) and HOP(O)(OR)2 obtained by the practical reaction of phosphorus pentoxide and alcohol (ROH) could also be converted in two additional steps into the corresponding trialkyl esters. The three-step synthesis of trialkylphosphates starting from phosphorus pentoxide was also transformed in a one-pot (step 1: preparation of the monoester diester mixture, step 2: diesterification) and telescoping (step 3: triesterification) variation, avoiding the isolation and purification of the intermediates, and affording the triesters­ in 86–93% yields. The three- and two-step P-chloride-free methods developed are ‘green’ and of more general value.
      Citation: Synthesis ; : -
      PubDate: 2022-03-30T00:00:00+01:00
      DOI: 10.1055/a-1811-8586
       
  • Assembly of the Hydroxycinnoline Core via Hydrazide-Assisted
           Rh(III)-Catalyzed C–H Functionalization and Annulation

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      Authors: Kim; Suho, Park, Heon Kyu, Kang, Ju Young, Mishra, Neeraj Kumar, Kim, In Su
      Abstract: The structural modification of phthalazinones and indazolones has emerged as a pivotal topic in catalytic C–H functionalization events. Herein we report the hydrazide-assisted rhodium(III)-catalyzed cross-coupling reactions of N-arylphthalazinones and N-arylindazolones with vinylene carbonate. This method provides direct access to tetracyclic hydroxycinnolines. Complete site-selectivity and functional group compatibility were observed.
      Citation: Synthesis ; : -
      PubDate: 2022-03-30T00:00:00+01:00
      DOI: 10.1055/a-1811-7948
       
  • Synthesis of Phosphoramidate Prodrugs of Phenolic Natural Products and
           Drugs by Ester Exchange

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      Authors: Yao; Jie, Huang, Chengjie, Wu, Fan, Zhao, Yufen, Ni, Feng
      Abstract: Drug development based on phenolic natural products as drug candidates against various diseases has gained much attention in recent years. However, most of those molecules lack therapeutic efficacy in clinical trials, usually due to poor bioavailability. Therefore, a prodrug approach was adopted to address the bioavailability problem of phenolic drugs. This paper describes a mild and convenient method for late-stage ProTide-type prodrug synthesis of phenolic pharmaceuticals, which gives various phosphoramidate prodrugs from unprotected phenolic natural products and drugs in high yield. More importantly, this reaction is amenable for the selective phosphorylation of the phenolic hydroxyl group in the presence of otherwise problematic nucleophilic functional groups like amines and alcohols. We also observed that the chemical release rate of the phenol can be substantially tuned by changing the amino acid residue on the phosphoramidate moiety.
      Citation: Synthesis ; : -
      PubDate: 2022-03-30T00:00:00+01:00
      DOI: 10.1055/s-0041-1737911
       
  • Facile One-Pot Preparation of 5-Substituted 4-Iodo-1-tosylpyrazoles from
           N-Propargyl-N′-tosylhydrazines through Iodocyclization

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      Authors: Saito; Aya, Yoshida, Kazuhiro, Togo, Hideo
      Abstract: Treatment of N-propargyl-N′-tosylhydrazines with molecular iodine (I2) in the presence of NaHCO3 under warming conditions gave efficiently the corresponding 5-substituted 4-iodo-1-tosylpyrazoles in good to moderate yields. In addition, the same reaction in the presence of acetic acid generated the corresponding 5-aryl-4-iodopyrazoles in moderate yields. The reactions are simple and efficient transition-metal-free methods for the preparation of 5-substituted 4-iodo­pyrazole unit.
      Citation: Synthesis ; : -
      PubDate: 2022-03-28T00:00:00+01:00
      DOI: 10.1055/s-0041-1737395
       
  • Flow Hydrogenation of 1,3,5-Trinitrobenzenes over Cu-Based Catalysts as an
           Efficient Approach for the Preparation of Phloroglucinol Derivatives

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      Authors: Nuzhdin; Alexey L., Shchurova, Irina А., Bukhtiyarova, Marina V., Bulavchenko, Olga A., Alekseyeva, Natalia A., Sysolyatin, Sergey V., Bukhtiyarova, Galina A.
      Abstract: An environmentally friendly and safe synthesis of phloroglucinol and its derivatives through the flow hydrogenation of 1,3,5-trinitrobenzenes on heterogeneous copper catalysts is reported. It was found that hydrogenation of 1,3,5-trinitrobenzene, 2,4,6-trinitrotoluene, 2,4,6-trinitroxylene, and 2,4,6-trinitromesitylene in methanol over Cu–Al mixed oxides derived from layered double hydroxides led to selective formation of the corresponding triaminobenzenes, which were isolated from the reaction mixture in the form of double salts with sulfuric acid and were stable in storage. Subsequent hydrolysis in aqueous solution gave the phloroglucinol derivatives in good yields (75–82%).
      Citation: Synthesis ; : -
      PubDate: 2022-03-23T00:00:00+0100
      DOI: 10.1055/a-1807-3188
       
  • Mechanisms of the Nickel-Catalysed Hydrogenolysis and Cross-Coupling of
           Aryl Ethers

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      Authors: Borys; Andryj M., Hevia, Eva
      Abstract: The Ni-catalysed hydrogenolysis and cross-coupling of aryl ethers has emerged as a powerful synthetic tool to transform inert phenol-derived electrophiles into functionalised aromatic molecules. This has attracted significant interest due to its potential to convert the lignin fraction of biomass into chemical feedstocks, or to enable orthogonal reactivity and late-stage synthetic modification. Although the scope of nucleophiles employed, and hence the C–C and C–heteroatom bonds that can be forged, has expanded significantly since Wenkert’s seminal work in 1979, mechanistic understanding on how these reactions operate is still uncertain since the comparatively inert Caryl–O bond of aryl ethers challenge the involvement of classical mechanisms involving direct oxidative addition to Ni(0). In this review, we document the different mechanisms that have been proposed in the Ni-catalysed hydrogenolysis and cross-coupling of aryl ethers. These include: (i) direct oxidative addition; (ii) Lewis acid assisted C–O bond cleavage; (iii) anionic nickelates, and; (iv) Ni(I) intermediates. Experimental and theoretical investigations by numerous research groups have generated a pool of knowledge that will undoubtedly facilitate future discoveries in the development of novel Ni-catalysed transformations of aryl ethers.1 Introduction2 Direct Oxidative Addition3 Hydrogenolysis of Aryl Ethers4 Lewis Acid Assisted C–O Bond Cleavage5 Anionic Nickelates6 Ni(I) Intermediates7 The ‘Naphthalene Problem’8 Conclusions and Outlook
      Citation: Synthesis ; : -
      PubDate: 2022-03-23T00:00:00+0100
      DOI: 10.1055/a-1806-4513
       
  • Recyclable Hypervalent Iodine Reagents in Modern Organic Synthesis

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      Authors: Rimi; Rimi, Soni, Sakshi, Uttam, Bhawna, China, Hideyasu, Dohi, Toshifumi, Zhdankin, Viktor V, Kumar, Ravi
      Abstract: Hypervalent iodine (HVI) reagents have gained much attention as versatile oxidants because of their low toxicity, mild reactivity, easy handling, and availability. Despite their unique reactivity and other advantageous properties, stoichiometric HVI reagents are associated with the disadvantage of generating non-recyclable iodoarenes as waste/co-products. To overcome these drawbacks, the syntheses and utilization of various recyclable hypervalent iodine reagents have been established in recent years. This review summarizes the development of various recyclable non-polymeric, polymer-supported, ionic-liquid-supported, and metal–organic framework (MOF)-hybridized HVI reagents.1 Introduction2 Polymer-Supported Hypervalent Iodine Reagents2.1 Polymer-Supported Hypervalent Iodine(III) Reagents2.2 Polymer-Supported Hypervalent Iodine(V) Reagents3 Non-Polymeric Recyclable Hypervalent Iodine Reagents3.1 Non-Polymeric Recyclable Hypervalent Iodine(III) Reagents3.2 Recyclable Non-Polymeric Hypervalent Iodine(V) Reagents3.3 Fluorous Hypervalent Iodine Reagents4 Ionic-Liquid/Ion-Supported Hypervalent Iodine Reagents5 Metal–Organic Framework (MOF)-Hybridized Hypervalent Iodine Reagents6 Conclusion
      Citation: Synthesis ; : -
      PubDate: 2022-03-23T00:00:00+0100
      DOI: 10.1055/s-0041-1737909
       
  • Stereoselective Synthesis and Applications of Pinane-Based Chiral
           1,4-Amino Alcohol Derivatives

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      Authors: Raji; Mounir, Le, Tam Minh, Csámpai, Antal, Nagy, Viktória, Zupkó, István, Szakonyi, Zsolt
      Abstract: A new library of pinane-based 1,4-amino alcohols was synthesised and utilised as chiral ligands in enantioselective diethylzinc addition to benzaldehyde. Aldol condensation of (+)-nopinone, derived from (–)-β-pinene, with 2-pyridinecarboxaldehyde gave the key intermediate α,β-unsaturated ketone, which was transformed in diastereoselective reduction, followed by hydrogenation, resulting in 1,4-amino alcohols. On the other hand, epoxidation of the α,β-unsaturated ketone, followed by reduction and then hydrogenation of the pyridine ring, afforded a mixture of 4-amino-2,3-epoxy-1-ols. Stereoselective hydride reduction of the epoxy ketone and subsequent condensation of the resulting products with substituted benzyl bromides provided quaternary ammonium salts, which were subjected to hydride reduction and then hydrogenation, affording 4-amino-2,3-epoxy-1-ol derivatives containing an N-benzylpiperidine moiety. The inhibition of nucleophile-initiated opening of the oxirane ring was interpreted by a systematic series­ of comparative Hartree–Fock modelling study using the 6-31+G(d,p) basis set. The antiproliferative activities of 4-amino-2,3-epoxy­-1-ol derivatives were examined, and structure–activity relationships were studied from the aspects of the stereochemistry of the oxirane ring, saturation, and substituent effects on the piperidine ring system.
      Citation: Synthesis ; : -
      PubDate: 2022-03-23T00:00:00+0100
      DOI: 10.1055/s-0040-1719887
       
  • Synthesis of Diaza[5]helicenes by ortho,ortho′-Fusion of
           ortho-Terphenyls

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      Authors: Herzog; Stefan, Marten, Inka, Weiß, Aaron, Podlech, Joachim
      Abstract: Double ortho-fusion in suitably substituted ortho-terphenyls was used for the synthesis of diaza[5]helicenes. Bis(carboxamido)-substituted ortho-terphenyls can be condensed to 5,9- and 6,9-diaza[5]helicenes, where substituents at the 6,10- and 5,10-positions, respectively­, are introduced with the carboxamido groups. While a twofold­ coupling sequence with intermediate protection of one amino group has to be used for 5,9-diaza[5]helicenes, a more concise sequence avoiding the protection leads to 6,9-diaza[5]helicenes. The simple heating of ortho,ortho′-diazidoterphenyls furnishes 5,8-dihydroindolo[2,3-c]carbazoles, i.e., [5]helicenes with alternating benzene and pyrrole rings.
      Citation: Synthesis ; : -
      PubDate: 2022-03-22T00:00:00+0100
      DOI: 10.1055/a-1804-8980
       
  • Radical Oxyazidation of Alkenes in Pure Water

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      Authors: Cui; Jinfeng, Zhou, Huan, Li, Yajun, Bao, Hongli
      Abstract: Compared to universal radical difunctionalizations of alkenes that are performed with organic solvents, such reactions with water as the sole solvent are rarely reported. Concerning the global consensus on environmental issues, we have developed herein a method for the radical oxyazidation of alkenes in pure water. This reaction allows the construction of C–N and C–O bonds in a one-pot process. Styrenes, 1,3-dienes, and unactivated alkenes react smoothly under mild and environmentally benign conditions to afford a wide scope of functionalized azides in excellent yields and selectivities.
      Citation: Synthesis ; : -
      PubDate: 2022-03-22T00:00:00+0100
      DOI: 10.1055/a-1804-8859
       
  • Synthesis of P- and S-Stereogenic Compounds via Enantioselective C–H
           Functionalization

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      Authors: Qian; Pu-Fan, Li, Jun-Yi, Zhou, Tao, Shi, Bing-Feng
      Abstract: Transition metal-catalyzed enantioselective C–H functionalization has emerged as an efficient and powerful strategy to access various chiral molecules. Recently, this strategy has also provided a complementary pathway to the construction of P- and S-stereogenic compounds. In this short review, we summarize the development and applications of various catalytic systems: Pd(II)/mono-N-protected amino acids (MPAA), Pd(0)/trivalent phosphorus chiral ligands, chiral cyclopentadienyl-ligated metal catalysts [CpxM(III)] (M = Rh, Ir), half-sandwich d6 Ir(III) and Ru(II) with a chiral carboxylic acid (CCA) ligand, Ir(I)/chiral bidentate boryl ligand, and Ir(I)/chiral cation, for accessing these chiral compounds via enantioselective C–H functionalization. 1 Introduction2 Pd(II)/Mono-N-protected Amino Acids3 Pd(0)/Trivalent Phosphorus Chiral Ligands4 Chiral Cyclopentadienyl-Ligated Metal Catalysts [CpxM(III)] (M = Rh, Ir)5 Half-sandwich d6 Ir(III) and Ru(II) with a Chiral Carboxylic Acid (CCA) Ligand6 Ir(I)/Chiral Bidentate Boryl Ligand7 Ir(I)/Chiral Cation8 Conclusion and Outlook
      Citation: Synthesis ; : -
      PubDate: 2022-03-18T00:00:00+0100
      DOI: 10.1055/a-1802-6793
       
  • Palladium-Catalyzed Three-Component 1,4-Carboarylation of 1,3-Enynes with
           Malonic Esters and Aryl Iodides

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      Authors: Bao; Jingjing, Wei, Rongbiao, Li, Yajun, Bao, Hongli
      Abstract: Ionic 1,4-difunctionalization of 1,3-enynes has often been conducted with strong nucleophiles or 1,3-enynes that are activated by an electron-withdrawing group. In this work, a palladium-catalyzed three-component ionic 1,4-carboarylation of 1,3-enynes is reported with arylated 1,3-enynes as the substrates. This method can afford various tetrasubstituted allenes with different functionalities. The palladium salt might play a key dual role in the reaction: as the catalyst to catalyze the cross-coupling reaction and as a Lewis acid to facilitate the nucleophilic attack. The synthetic value of this method is demonstrated by the further cyclization, decoration, and hydrolysis of the allene products.
      Citation: Synthesis ; : -
      PubDate: 2022-03-17T00:00:00+0100
      DOI: 10.1055/a-1801-3656
       
  • Enantioselective Cobalt-Catalyzed C–H Functionalization

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      Authors: Xu; Weiwei, Ye, Mengchun
      Abstract: Co-catalyzed C–H functionalization has received great attention due to the high earth abundance, low biotoxicity, and unique reactivity of cobalt; enantioselective control of these reactions has been a formidable challenge. Various efficient strategies have recently been developed for enantioselective Co-catalyzed C–H functionalization, but there is no topical review of this field. Herein, we give a detailed summary of this rapidly growing field, highlighting critical progress, current challenges, and future trends.1 Introduction2 Enantioselective C–H Functionalization via Low-Valent Co Catalysis2.1 Chiral Diphosphines for Enantioselective Control2.2 Chiral Monophosphines or N-Heterocyclic Carbenes for Enantioselective Control3 Enantioselective C–H Functionalization via High-Valent Co Catalysis3.1 Chiral Acids for Enantioselective Control3.2 Chiral Cp Ligands for Enantioselective Control4 Conclusions and Outlook
      Citation: Synthesis ; : -
      PubDate: 2022-03-17T00:00:00+0100
      DOI: 10.1055/a-1801-2595
       
  • Synthesis of New Fused 4H-Thieno[3,2-b]pyrrole Derivatives via
           Decomposition of Methyl 4-Azido-5-arylthiophene-2-carboxylates

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      Authors: Samsonenko; Anna L., Kostyuchenko, Anastasia S., Zheleznova, Tatyana Yu., Shuvalov, Vladislav Yu., Vlasov, Igor S., Fisyuk, Alexander S.
      Abstract: This article is focused on the development of practical approaches to the synthesis of 4-azido-5-arylthiophene-2-carboxylates and 4-amino-5-arylthiophene-2-carboxylates using the Fiesselmann reaction. The photochemical and thermal (including microwave-assisted) decomposition of 4-azido-5-arylthiophene-2-carboxylates have been studied in order to synthesize fused 4H-thieno[3,2-b]pyrrole derivatives. The proposed approaches allow to obtain functionally substituted heteroacenes, which are of interest as building blocks for organic semiconductors.
      Citation: Synthesis ; : -
      PubDate: 2022-03-16T00:00:00+0100
      DOI: 10.1055/a-1799-9339
       
  • Photocatalytic Approach to α,α-Difluoroalkyl Alcohols

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      Authors: Kachkovskyi; Georgii, Cieślak, Marcin, Graczyk, Piotr, Zawadzki, Przemysław, Kalinowska-Tłuścik, Justyna, Werłos, Mateusz
      Abstract: A convenient approach to previously poorly accessible α,α-difluoroalkyl alcohols by visible light-mediated photocatalysis was developed. Broad scope of the transformation together with experimental simplicity and scalability using flow techniques open good prospects for further studies of properties (including biological) of these novel products.
      Citation: Synthesis ; : -
      PubDate: 2022-03-16T00:00:00+0100
      DOI: 10.1055/s-0041-1737546
       
  • Eight-Step Asymmetric Synthesis of (–)-Berkelic Acid

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      Authors: Yang; Zhenjie, Cheng, Hong-Gang, Chen, Ruiming, Cao, Liming, Wei, Qiang, Wang, Qingqing, Zhou, Qianghui
      Abstract: We herein report an eight-step asymmetric synthesis of (–)-berkelic acid. This work features a sequential Catellani-type reaction/oxa-Michael addition with epoxides as dual-functionalized alkylating reagents for synthesizing the isochroman framework, a one-pot, acid-catalyzed deprotection/spiroacetalization process for the construction of a tetracyclic core intermediate, and a late-stage Ni-catalyzed reductive coupling reaction for the installation of the side chain. Remarkably, during the deprotection/spiroacetalization process, four new stereocenters are created with high stereocontrol from a single existing chiral center.
      Citation: Synthesis ; : -
      PubDate: 2022-03-15T00:00:00+0100
      DOI: 10.1055/a-1799-0459
       
  • Practical Synthesis of Variously Substituted 2,3,4-Benzothiadiazepine
           2,2-Dioxides

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      Authors: Nyulasi; Bálint, Teski, Tamara, Németh, András Gy., Sprőber, Sára, Simig, Gyula, Volk, Balázs
      Abstract: The significant pharmacological activity of 2,3-benzodiazepine-4-ones led to an increased interest in this compound family. However, the literature of the closely related 2,3,4-benzothiadiazepine 2,2-dioxides is rather scarce. Earlier we elaborated a synthesis of 5-aryl congeners variously substituted at the aromatic ring. In the present study, a new synthetic route was investigated via highly versatile intermediates, to extend the reaction to a wider aromatic substitution pattern and to the preparation of 5-alkyl and 5-H derivatives. The essence of this approach is, starting from benzaldehyde acetals, acetophenone and benzophenone ketals, to synthesize ortho-formyl- and ortho-acyl-arylmethanesulfonyl chlorides, which are suitable precursors of the target compounds. The synthesis was implemented as follows: ortho-lithiation of the corresponding acetals and ketals and subsequent treatment with paraformaldehyde, or alternatively in two steps, with DMF or ethyl formate, followed by reduction with NaBH4, led to the corresponding hydroxymethyl derivatives. Reaction of these latter with methanesulfonyl chloride gave mesylates that were used to S-alkylate thiourea to afford S-alkylisothiouronium salts. The final steps of the synthesis were carried out in a telescoped reaction. Treatment of the S-alkylisothiouronium salts with N-chlorosuccinimide resulted in the corresponding arylmethanesulfonyl chlorides. Subsequent reaction with hydrazine hydrate followed by an acidic treatment gave 2,3,4-benzothiadiazepine 2,2-dioxides.
      Citation: Synthesis ; : -
      PubDate: 2022-03-14T00:00:00+0100
      DOI: 10.1055/a-1797-5298
       
  • Epoxydibenzo[b,f][1,5]diazocines: From a Hidden Structural Motif to an
           Efficient Solvent-Free Synthetic Protocol

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      Authors: Depa; Wojciech, Bisek, Bartosz, Górecki, Marcin, Michalak, Michał
      Abstract: Epoxydiazocines belong to the rare class of small V-shaped molecules, closely related to Tröger’s base. Due to their intriguing, unique structure, they could serve as molecular building blocks for supramolecular chemistry. An extensive review on their synthesis is contained in this article. Moreover, our recent findings devoted to efficient and easily scalable synthesis of fluorinated epoxy[1,5][b,f]diazocines through solvent-free base-catalyzed condensation of ortho-aminophenones is provided. The unique V-shaped structure was confirmed by X-ray crystal structure analysis. Furthermore, the rigidity of the epoxy­diazocine skeleton allowed for racemate separation and the configuration of enantiomers was established by combining quantum chemical calculations and chiroptical methods.1 Introduction2 Synthetic Efforts Towards Epoxydibenzo[b,f][1,5]diazocines3 Synthetic Efforts Towards Fluorinated Epoxydibenzo[b,f][1,5]diazocines4 Conclusion
      Citation: Synthesis ; : -
      PubDate: 2022-03-14T00:00:00+0100
      DOI: 10.1055/s-0040-1719908
       
  • The Povarov Reaction: A Versatile Method to Synthesize
           Tetrahydroquinolines, Quinolines and Julolidines

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      Authors: Ferreira de Paiva; Walysson, de Freitas Rego, Yuri, de Fátima, Ângelo, Fernandes, Sergio Antonio
      Abstract: The multicomponent Povarov reaction represents a powerful approach for the construction of substances containing N-heterocyclic frameworks. By using the Povarov reaction, in addition to accessing tetrahydroquinolines, quinolines and julolidines in a single step, it is possible to form the following new bonds: two Csp 3–Csp 3 and one Csp 3–Nsp 3, two Csp 2–Csp 2 and one Csp 2–Nsp 2, and four Csp 3–Csp 3 and two Csp 3–Nsp 1, respectively. This short review discusses the main features of the Povarov reaction, including its mechanism, the reaction scope by employing different catalysts and substrates, as well as stereoselective versions.1 Introduction2 Mechanism of the Povarov Reaction3 Tetrahydroquinolines4 Quinolines5 Julolidines6 Concluding Remarks
      Citation: Synthesis ; : -
      PubDate: 2022-03-10T00:00:00+0100
      DOI: 10.1055/a-1794-8355
       
  • Facile Access to Spiro[4.5]decanes through Oxidative
           Dearomatization-Induced Ring Expansion of Cyclobutanes

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      Authors: Xi; Shuang, Zhang, Jingyang, Guo, Zhen, Zu, Yumeng, Liu, Yang, Wang, Gelin, Tang, Yefeng
      Abstract: A mechanistically interesting and practical method for the synthesis of functionalized spiro[4.5]decanes is developed, featuring oxidative dearomatization-induced ring expansion of cyclobutanes as the key element. The new method enables facile access to a variety of spiro[4.5]cyclohexadienones with good efficiency and generality. Further elaboration of the resulting products into other valuable scaffolds is also explored, leading to the discovery of an interesting compound that displays a promising biological profile. Moreover, we have also conducted a comprehensive computational study that provides a deep insight into the mechanism of the reaction.
      Citation: Synthesis ; : -
      PubDate: 2022-03-10T00:00:00+0100
      DOI: 10.1055/a-1794-0770
       
  • Halocyclobutanol Dehydration En Route to Halocyclobutenes

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      Authors: Oeser; Petr, Petrenko, Artem, Edlová, Tereza, Čubiňák, Marek, Koudelka, Jakub, Tobrman, Tomáš
      Abstract: A new method for the preparation of halocyclobutenes is described. The developed process involves the dehydration of halocyclobutanols by using tetrafluoroboric acid–diethyl ether complex in dichloromethane at room temperature. The process allows for high yields of halocyclobutenes to be achieved by using alcohols that do not trigger the formation of isomeric allylic halides.
      Citation: Synthesis ; : -
      PubDate: 2022-03-10T00:00:00+0100
      DOI: 10.1055/a-1794-0685
       
  • Cobalt(III)-Catalyzed C–H Activation/Annulation Cascade Reaction of
           N-Chlorobenzamides with 2-Acetylenic Ketones at Room Temperature

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      Authors: Wu; Zhouping, Zheng, Qinwen, Lv, Guanghui, Lai, Ruizhi, Hu, Yao, Hai, Li, Wu, Yong
      Abstract: A mild cascade annulation of Co(III)-catalyzed N-chlorobenz­amides with 2-acetylenic ketones at room temperature is reported. This reaction sets N–Cl bond of N-chlorobenzamide as an internal oxidant, displaying broad functional group tolerance and excellent reverse selectivity of alkyne insertion under mild and safe conditions. The cascade reaction offers a straightforward and mild protocol to construct isoquinolones in high yields at room temperature.
      Citation: Synthesis ; : -
      PubDate: 2022-03-10T00:00:00+0100
      DOI: 10.1055/a-1794-1314
       
  • Rhodium(III)-Catalyzed Synthesis of Quinazolin-4(3H)-ones with
           N-Methoxyamides as Synthesis Reagents

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      Authors: Zhou; Guanyu, Huang, Zhibin, Xu, Xu, Fang, Zhang, Huang, Pengcheng, Deng, Zefeng, Li, Bao, Zhao, Yingsheng
      Abstract: A practical method to synthesize quinoxalinones via intra/intermolecular amination using rhodium as the catalyst was developed. A wide variety of quinoxalinones were prepared from N-methoxybenzamides in moderate to excellent yields. Gram-scale reactions were also achieved, highlighting the synthetic importance of this new transformation.
      Citation: Synthesis ; : -
      PubDate: 2022-03-09T00:00:00+0100
      DOI: 10.1055/a-1792-9930
       
  • Pd-Catalyzed N–H or C–H Functionalization/Oxidative Cyclization for
           the Efficient Synthesis of N-Aryl-Substituted [3,4]-Fused
           Pyrrolo­coumarins

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      Authors: Balalas; Thomas D., Kanelli, Maria G., Gabriel, Catherine, Pontiki, Eleni, Hadjipavlou-Litina, Dimitra J., Litinas, Konstantinos E.
      Abstract: 1-Aryl-2-methyl- or 3-methylchromeno[4,3-b]pyrrol-4(1H)-ones have been synthesized in excellent yields by the Pd-catalyzed intramolecular aza-Wacker-type cyclization of 3-allyl-4-arylaminocoumarins or C–H insertion/oxidative cyclization of N-allyl-N-aryl-4-aminocoumarins, respectively, in the presence of Cu(OAc)2 in acetic acid under heating. The starting allylcoumarins have been prepared by the allylation of 4-arylaminocoumarins with allyl bromide in CH3CN in the presence of Cs2CO3 at room temperature. Preliminary biological tests indicated interesting antioxidant activity and significant levels of inhibition of soybean lipoxygenase.
      Citation: Synthesis ; : -
      PubDate: 2022-03-09T00:00:00+0100
      DOI: 10.1055/s-0037-1610793
       
  • Rhodium-Catalyzed C–H Activation of Indoles for the Construction of
           Spiroindole Scaffolds

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      Authors: Wang; Huiying, Wang, Mengmeng, Ma, Biao, Dai, Hui-Xiong
      Abstract: Spiroindoles are key scaffolds in a large number of natural products, pharmaceuticals, and agrochemicals. Selective C–H activation has emerged as a powerful synthetic approach to streamline the synthesis of substituted spiroindoles. To date, various 2- and 3-indolyl-tethered aza-spiro-centers have been successfully achieved via C–H activation. However, introduction of spiro-containing systems onto the benzenoid core of indole still remains challenging. Herein, a method of Rh(III)-catalyzed selective C7-H activation/cyclization of indole with maleimide to afford novel spiroindole derivatives is reported, which incorporate both succinimide and spirocycle into indole unit. Gram-scale synthesis demonstrates the utility of this protocol, further modification via click chemistry offered a novel scaffold as a versatile spiro linker.
      Citation: Synthesis ; : -
      PubDate: 2022-03-08T00:00:00+0100
      DOI: 10.1055/a-1791-7218
       
  • Facile Access to α-Substituted β-Thio Enals from 1,2,3-Triazines
           and Thiols

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      Authors: Luo; Han, Lu, Qixing, Xu, Mingchuan, Gu, Mingxi, Li, Baosheng
      Abstract: Herein, a chemoselective cascade addition reaction is reported, which starts from 1,2,3-triazines and thiols to access several different α-substituted β-thio enals and their derivatives in a green and efficient synthesis. In terms of applications, readily available substrates, diversity of products, and mild reaction system make this strategy highly attractive.
      Citation: Synthesis ; : -
      PubDate: 2022-03-07T00:00:00+0100
      DOI: 10.1055/a-1790-2282
       
  • Rhodium(I)-Catalyzed Regioselective C–H Alkenylation of
           2,2′-Bipyridine Derivatives with Alkynes

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      Authors: Yu; Jia, Wen, Si, Tian, Qingyu, Chen, Yanhui, Cheng, Guolin
      Abstract: In this work, a Rh(I)-catalyzed C3-alkenylation of 2,2′-bipyri­dine-6-carboxamide with terminal and internal alkynes was developed, providing an efficient access to a broad range of alkenylated 2,2′-bipyridine derivatives with exclusive regioselectivity and stereoselectivity. Deuterium labeling experiments indicate that an irreversible rollover C–H activation process is involved in this reaction.
      Citation: Synthesis ; : -
      PubDate: 2022-03-07T00:00:00+0100
      DOI: 10.1055/a-1790-0869
       
  • Tryptanthrin and Its Derivatives in Drug Discovery: Synthetic Insights

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      Authors: Brandão; Pedro, Pineiro, Marta, Burke, Anthony J.
      Abstract: Tryptanthrin is a golden-yellow, naturally occurring alkaloid that can be obtained from multiple sources and through different synthetic methodologies. This tetracyclic compound displays several relevant biological activities. The potential of this tetracyclic alkaloid has been widely explored, and several researchers have focused their attention on expanding the variety of tryptanthrin derivatives by using a range of synthetic strategies. In this short review, we aim to address recent developments in the synthesis of the tryptanthrin core, as well as the development of new strategies employed by synthetic organic chemists to obtain novel tryptanthrin derivatives with potential biological activity, using different tools from the chemists’ toolbox, such as photocatalysis, solvent-free approaches, and multicomponent reactions.
      Citation: Synthesis ; : -
      PubDate: 2022-03-07T00:00:00+0100
      DOI: 10.1055/s-0040-1719901
       
  • Rh(III)-Catalyzed Tandem [4+2] Annulation To Construct Functional
           Dihydroisoquinolinones

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      Authors: Yang; Jia-Hui, Dong, Lin
      Abstract: A highly efficient Rh(III)-catalyzed tandem [4+2] annulation to construct functional dihydroisoquinolinone derivatives with an alkenyl side chain by insertion into an N–O bond as an internal oxidation process has been achieved. A wide range of 1,3-dienes as the coupling partners makes this simple methodology even more useful.
      Citation: Synthesis ; : -
      PubDate: 2022-03-03T00:00:00+0100
      DOI: 10.1055/a-1787-3958
       
  • Heteroatom-Tethered ω-Alkenylallylboronates: Stereoselective Synthesis of
           Heterocyclic Derived Alcohols

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      Authors: Garnes-Portolés; Francisco, Miguélez, Rubén, Grayson, Matthew N., Barrio, Pablo
      Abstract: The synthesis of ω-alkenylallylboronates using a heteroatom tether to join both functional groups is described for the first time. Then, these unprecedented compounds were used in a tandem Brønsted acid catalyzed allylboration/ring-closing metathesis (RCM) reaction affording heterocyclic derived alcohols as single diastereoisomers. The low enantioselectivity observed in the asymmetric version using a chiral phosphoric acid catalyst was studied theoretically.
      Citation: Synthesis ; : -
      PubDate: 2022-03-03T00:00:00+0100
      DOI: 10.1055/s-0040-1719890
       
  • Design, Synthesis, and Screening of Pyridothieno[3,2-b]indole and
           Pyridothieno[3,2-c]cinnoline Derivatives as Potential Biologically Active
           Molecules

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      Authors: Vasilin; Vladimir K., Kanishcheva, Eugeniya A., Stroganova, Tatyana A., Dmitrieva, Irina G., Taranenko, Viktor V., Tumskiy, Roman S., Tumskaia, Anastasiia V., Aksenov, Nikolay A., Krapivin, Gennady D.
      Abstract: New pyridothieno[3,2-b]indole and pyridothieno[3,2-c]cinnoline derivatives are designed and prepared from the corresponding 3-amino-2-arylthieno[2,3-b]pyridines. By a molecular docking method novel potential inhibitors of DNA gyrase B are identified among the thieno[2,3-b]pyridine derivatives. In addition, some of the prepared pyridothienoindoles exhibit in vivo antidote activity against the herbicide 2,4-D.
      Citation: Synthesis ; : -
      PubDate: 2022-03-02T00:00:00+0100
      DOI: 10.1055/a-1785-7191
       
  • On the Copper-Promoted Backbone Arylation of Histidine-Containing Peptides
           Using Triarylbismuthines

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      Authors: Chan; Hwai-Chien, Gagnon, Alexandre
      Abstract: We report herein our detailed investigation on the histidine-directed backbone arylation of histidine-containing peptides using triarylbismuth reagents. The reaction proceeds on the backbone NH of the amino acid that precedes the histidine, the so-called n–1 position. The protocol is applicable to dipeptides where the histidine is located at the C-terminus and to tripeptides where the histidine occupies the central position. The transformation is promoted by copper(II) acetate in the presence of phenanthroline (Phen) and diisopropylethylamine in dichloromethane at 50 °C under oxygen. An excellent scope was observed for the triarylbismuthines. In all cases, the imidazole ring of the histidine is protected with a trityl group to prevent the arylation of the side chain. An ATCUN-like model is proposed to explain the observed results.
      Citation: Synthesis ; : -
      PubDate: 2022-03-02T00:00:00+0100
      DOI: 10.1055/a-1786-6578
       
  • Rhodol-Based Fluorescent Probes Used for Fast Response toward ClO– and
           Delayed Determination of H2O2 in Living Cells

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      Authors: Wang; Bo, Zhang, Lanlan, Zheng, Jianpei, Bao, Hongli, Li, Daliang
      Abstract: Reactive oxygen species (ROS), a class of reactive oxidants, play critical roles in signal transduction, cell metabolism, immune defense, and other physiological processes. Abnormally excessive levels of ROS can cause diseases and thus, investigations into the relevant biology and medicine are significant. The behavior of ROS in inflammation has been rarely elucidated. In this work, two ROS fluorescent probes, FS-ROS1 and FS-ROS2 have been designed and synthesized. FS-ROS1 responds rapidly (~1 min) to ClO– and gradually (~30 min) to H2O2 with an increase in fluorescence at ~656 nm and 640 nm of more than 100-fold in vitro. At a concentration of 10 μM, FS-ROS1 labels the L929 cell and Raw264.7 cell wells in 30 min with excellent biocompatibility and without washing. After labelling, FS-ROS1 exhibited a rational fluorescence increase upon the addition of 1, 10, 100, and 200 μM of H2O2. Based on these results, inflammatory cells, stimulated with 800 nM dexamethasone and polyIC, showed a higher increase in fluorescence than the control cells. These results suggest that H2O2 and ClO– might be important signaling molecules during inflammations.
      Citation: Synthesis ; : -
      PubDate: 2022-03-02T00:00:00+0100
      DOI: 10.1055/a-1786-1584
       
  • Visible-Light-Induced Catalysis: A Regioselectivity Switch between [2+1]
           and [2+2] Cycloaddition of Diazocarbonyls with Olefins

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      Authors: Qiu; Huixin, Wen, Lirong, Lv, Jian
      Abstract: Visible-light-promoted [2+1] and [2+2] cycloaddition reactions of diazocarbonyls with olefins have been developed, affording functionalized cyclopropanes and cyclobutanes, respectively. In visible-light catalysis of Ir(ppy)3, a simple addition of Rh2(OAc)4 switches the regioselectivity from [2+1] to [2+2] cycloaddition with good reactivity and high regioselectivity.
      Citation: Synthesis ; : -
      PubDate: 2022-03-02T00:00:00+0100
      DOI: 10.1055/a-1786-6496
       
  • Direct Synthesis of Disubstituted Trifluoromethylthiolated Alkenes

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      Authors: Fichez; Jeanne, Dupommier, Dorian, Besset, Tatiana
      Abstract: In the field of organofluorine chemistry, the quest for emergent fluorinated groups is in high demand. In particular, the scientific community has shown special interest in the SCF3 residue thanks to its unique properties. Indeed, over the last decade, the SCF3 group has become a pivotal fluorinated moiety, as demonstrated by several SCF3-containing compounds of interest, and, related to that, the steadily increasing number of synthetic methods that are available to access such molecules. In this Short Review, the main advances made for the synthesis of trifluoromethylthiolated disubstituted alkenes will be discussed and highlighted.1 Introduction2 Trifluoromethylthiolation of Prefunctionalized Alkenes3 Direct C–H Trifluoromethylthiolation of Alkenes4 Trifluoromethylthiolation of Miscellaneous Derivatives5 Conclusion
      Citation: Synthesis ; : -
      PubDate: 2022-03-01T00:00:00+0100
      DOI: 10.1055/s-0040-1719891
       
  • Fluorinated Olefinic Lactams: The Case of Amino Acids – Preparation
           and Mechanistic Studies

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      Authors: Salamon-Krokosz; Katarzyna, Gołdyn, Mateusz, Siodła, Tomasz, Bartoszak-Adamska, Elżbieta, Koroniak, Henryk, Koroniak-Szejn, Katarzyna
      Abstract: Herein, we report the synthesis of analogues of amino acids with a monofluorovinyl moiety. Interestingly, we have found that cyclization of the obtained products proceeds easily in all cases. The cyclization process has not previously been observed at this reaction stage, and such fluorinated lactams derived from phenylalanine, valine, alanine have not been described before.
      Citation: Synthesis ; : -
      PubDate: 2022-03-01T00:00:00+0100
      DOI: 10.1055/s-0041-1737346
       
  • Advances in the Synthesis of Enterobactin, Artificial Analogues, and
           Enterobactin-Derived Antimicrobial Drug Conjugates and Imaging Tools for
           Infection Diagnosis

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      Authors: Klahn; Philipp, Zscherp, Robert, Jimidar, Claire C.
      Abstract: Iron is an essential growth factor for bacteria, but although highly abundant in nature, its bioavailability during infection in the human host or the environment is limited. Therefore, bacteria produce and secrete siderophores to ensure their supply of iron. The triscatecholate siderophore enterobactin and its glycosylated derivatives, the salmochelins, play a crucial role for iron acquisition in several bacteria. As these compounds can serve as carrier molecules for the design of antimicrobial siderophore drug conjugates as well as siderophore-derived tool compounds for the detection of infections with bacteria, their synthesis and the design of artificial analogues is of interest. In this review, we give an overview on the synthesis of enterobactin, biomimetic as well as totally artificial analogues, and related drug-conjugates covering up to 12/2021.1 Introduction2 Antibiotic Crisis and Sideromycins as Natural Templates for New Antimicrobial Drugs3 Biosynthesis of Enterobactin, Salmochelins, and Microcins4 Total Synthesis of Enterobactin and Salmochelins5 Chemoenzymatic Semi-synthesis of Salmochelins and Microcin E492m Derivatives6 Synthesis of Biomimetic Enterobactin Derivatives with Natural Tris-lactone Backbone7 Synthesis of Artificial Enterobactin Derivatives without Tris-lactone Backbone8 Conclusions
      Citation: Synthesis ; : -
      PubDate: 2022-02-28T00:00:00+0100
      DOI: 10.1055/a-1783-0751
       
  • Acrylamide-Based Pd-Nanoparticle Carriers as Smart Catalysts for the
           Suzuki–Miyaura Cross-Coupling of Amino Acids

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      Authors: Sabadasch; Viktor, Dachwitz, Steffen, Hannappel, Yvonne, Hellweg, Thomas, Sewald, Norbert
      Abstract: Polyacrylamide-based waterborne microgels were prepared with copolymerized carboxylic acid and tertiary amine moieties. The colloidal gels were loaded with palladium nanoparticles and utilized for the Suzuki–Miyaura cross-coupling of amino acids and peptides. The thermoresponsive properties of the prepared microgels were characterized by means of photon correlation spectroscopy (PCS) at solvent conditions of the catalytic reaction. The localization and morphology of the incorporated nanoparticles were characterized with transmission electron microscopy (TEM). Palladium-catalyzed Suzuki–Miyaura cross-coupling of N α-Boc-4-iodophenylalanine and N α-Boc-7-bromotryptophan with phenylboronic acid was carried out under ambient atmosphere in water at 20, 37, and 60 °C, respectively. The properties of the thermoresponsive microgel showed a strong influence on the reactivity and selectivity towards the respective substrate. For the amine containing microgels, a recyclability for up to four cycles without loss in activity could be realized. Furthermore, the systems showed good catalytic activity regarding Suzuki–Miyaura cross-coupling of halogenated amino acids in selected tri- and tetrapeptides.
      Citation: Synthesis ; : -
      PubDate: 2022-02-25T00:00:00+0100
      DOI: 10.1055/a-1782-4224
       
  • Asymmetric Brønsted Acid Catalyzed Cycloadditions of ortho-Quinone
           Methides and Related Compounds

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      Authors: Dorsch; Caroline, Schneider, Christoph
      Abstract: This review summarizes recent developments in the area of Brønsted acid catalyzed, enantioselective cycloadditions of ortho-quinone methides, ortho-quinone methide imines as well as heterocyclic indole- and pyrrole-based methides. In a straightforward and single-step transformation complex polycyclic N- and O-heterocyclic scaffolds are accessible, with typically good yields and excellent stereocontrol, from simple benzyl and heterobenzyl alcohols upon acid-catalyzed dehydration. The transient precursors are hydrogen-bonded to a chiral Brønsted acid which controls the enantioselectivity of the process.1 Introduction2 Cycloadditions of ortho-Quinone Methides2.1 Brønsted Acid Catalyzed Processes2.2 Cooperative Brønsted Acid/Transition-Metal-Catalyzed Processes3 Cycloadditions of ortho-Quinone Methide Imines4 Cycloadditions of Indolyl-3-methides5 Cycloadditions of Indolyl-2-methides5.1 Brønsted Acid Catalyzed Processes5.2 Cooperative Brønsted Acid/Transition-Metal-Catalyzed Processes6 Cycloadditions of Pyrrolyl-2-methides7 Cycloadditions of Pyrrolyl-3-methides8 Conclusions
      Citation: Synthesis ; : -
      PubDate: 2022-02-24T00:00:00+0100
      DOI: 10.1055/a-1781-6538
       
  • Biaryl Coupling of Aryldiazonium Salts and Arylboronic Acids Catalysed by
           Gold

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      Authors: Medina-Mercado; Ignacio, Porcel, Susana
      Abstract: A gold-catalysed coupling of aryldiazonium salts with arylboronic acids is described. The reactions proceed in satisfactory yields under irradiation with blue LEDs in the presence of KF and a catalytic amount of ascorbic acid. Notably, 4-nitrobenzendiazonium tetrafluoro­borate is sufficiently reactive to undergo the coupling with a variety of arylboronic acids in the absence of aryl radical initiators. The coupling is applicable for electron-donating and electron-withdrawing groups present at the para, ortho, and meta positions of both substrates.
      Citation: Synthesis ; : -
      PubDate: 2022-02-24T00:00:00+0100
      DOI: 10.1055/s-0041-1737882
       
  • Construction of Substituted [4]Acene Frameworks Based on Double Cationic
           Cyclizations of Fluoroalkenes

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      Authors: Takao; Go, Hakozaki, Tomohiro, Miura, Keisuke, Urushibara, Yusuke, Fuchibe, Kohei, Ichikawa, Junji
      Abstract: In this study, 5-substituted and 5,6-disubstituted [4]acenes were synthesized by the double cationic cyclization of fluoroalkenes. (a) After being treated with Me2AlCl (1.2 equiv), 2-trifluoromethyl-1-alkenes bearing two aryl groups underwent domino Friedel–Crafts-type cyclization (two-ring construction) followed by dehydrogenation to generate 5-fluorinated [4]acenes. The same (trifluoromethyl)alkenes were treated with both Me2AlCl (1.2 equiv) and Me3Al (1.0 equiv), resulting in selective one-ring construction and the creation of bicyclic 1,1-difluoro-1-alkenes. (b) When treated with triflic acid, the bicyclic difluoroalkenes underwent regioselective protonation to generate CF2 cations; Friedel–Crafts-type cyclization of these cations provided tetracyclic ketones. The obtained ketones act as an appropriate platform for the introduction of substituents at the 5-position of [4]acenes. (c) When treated with DDQ/H+, the bicyclic difluoroalkenes underwent oxidative generation of allylic CF2 cations; Friedel–Crafts-type cyclization of these cations produced tetracyclic enones. The enones were subjected to double addition of carbanions to facilitate the introduction of two substituents at the 5- and 6-positions of dihydro[4]acenes.
      Citation: Synthesis ; : -
      PubDate: 2022-02-24T00:00:00+0100
      DOI: 10.1055/s-0037-1610791
       
  • Iridium-Catalyzed Formal [4+1] Annulation of Benzamides and Cyclopropanols
           to Afford Isoindolin-1-one Derivatives via C–H Activation

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      Authors: Xu; Shuran, Luo, Cankun, Yan, Kaichuan, Li, Jianglian, Lai, Ruizhi, Hai, Li, Guan, Mei, Wu, Yong
      Abstract: An iridium-catalyzed reaction protocol has been developed to achieve the oxidative C–H/N–H annulation of benzamides with cyclopropanols as C1 synthon. Structurally diverse isoindolin-1-ones were furnished via sequential C–H/C–C cleavage and C–C/C–N bond formation.
      Citation: Synthesis ; : -
      PubDate: 2022-02-23T00:00:00+0100
      DOI: 10.1055/a-1780-1935
       
  • Reactions of α-Phenylglyoxylic Acids with ortho-Functionalized Anilines
           in Deep Eutectic Solvents: Selective Syntheses of
           3-Aryl-2H-benzo[b][1,4]oxazin-2-ones, 2-Arylbenzothiazoles, and
           3-Arylquinoxalin-2(1H)-ones

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      Authors: Jiang; Guofang, Chen, Guoqing, Yang, Jiangnan, Li, Hongxia, Chen, Zhongsheng, Xie, Zongbo, Le, Zhanggao
      Abstract: α-Phenylglyoxylic acid is a novel cyclization reagent. In this study, three cyclization products were synthesized by the reaction of α-phenylglyoxylic acids with ortho-functionalized anilines in deep eutectic solvents (DES). The five-membered-ring-formation products, the 2-arylbenzothiazoles, with a highest yield of 88%, were obtained by the reaction between 0.30 mmol of an o-aminothiophenol and 0.30 mmol of an α-phenylglyoxylic acid in choline chloride (ChCl)/d-(–)-tartaric acid DES at 60 °C for 0.5 h. The six-membered-ring-formation products, 3-aryl-2H-benzo[b][1,4]oxazin-2-one derivatives, were obtained in yields up to 99% by the reaction between 0.30 mmol of an o-aminophenol and 0.60 mmol of an α-phenylglyoxylic acid in ChCl/urea DES at 80 °C for 2.0 h. In the reaction between 0.30 mmol of o-phenylenediamine and 0.45 mmol of an α-phenylglyoxylic acid in ChCl/anhydrous tin(II) chloride DES at 70 °C for 1.5 h, the six-membered-ring-formation products, 3-arylquinoxalin-2(1H)-one derivatives, were synthesized, with a highest yield of 96%. This cyclization reaction occurred without the addition of other catalysts, and the title compounds were obtained with good yields under mild conditions.
      Citation: Synthesis ; : -
      PubDate: 2022-02-23T00:00:00+0100
      DOI: 10.1055/a-1780-1691
       
  • Stereoselective Synthesis of Dispirooxindoles Incorporating
           Pyrrolo[2,1-a]isoquinoline via [3+2] Cycloaddition of Azomethine Ylides
           with a Thiazolo[3,2-a]indole Dipolarophile

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      Authors: Thomas; Noble V., Meenakshy, C. B., Leena, Sruthi S., Deepthi, Ani
      Abstract: Highly regio- and stereoselective synthesis of dispiropyrrolo[2,1-a]isoquinoline-oxindoles have been developed by the one-pot three component reaction of isatins, 1,2,3,4-tetrahydroisoquinoline (THIQ), and a thiazolo[3,2-a]indole derivative. The reaction proceeds regioselectively through an exo-Re face approach of the in situ generated tetrahydroisoquinolium ylides towards the dipolarophile yielding the corresponding [3+2] cycloadducts in excellent yields and stereoselectivity.
      Citation: Synthesis ; : -
      PubDate: 2022-02-21T00:00:00+0100
      DOI: 10.1055/a-1777-2423
       
  • Synthetic Studies towards Pyrido[1,2-a]azepine Stemona Alkaloids

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      Authors: Morgenstern; Martin, Mayer, Camilla, Pöthig, Alexander, Bach, Thorsten
      Abstract: The carbon skeleton of the Stemona alkaloids stemokerrin and cochinchistemonine was assembled from three building blocks (a piperidine, a furan, and a tetronate). Key steps linking the fragments included a Stille cross-coupling (piperidine/furan) and an aldol-type addition of a tetronate. The furan served as a latent 1,4-difunctional compound which was converted into a γ-ketolactone by a type II photooxygenation. Attempts to construct the C12–C13 double bond of stemokerrin by a late-stage oxidation or by an elimination remained unsuccessful. The non-natural products dihydrostemokerrin and furostemokerrin were obtained instead.
      Citation: Synthesis ; : -
      PubDate: 2022-02-21T00:00:00+0100
      DOI: 10.1055/a-1777-2477
       
  • Properties and Synthetic Performances of Phenylamino Cyanoarenes under
           One-Photon Excitation Manifolds

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      Authors: Bortolato; Tommaso, Dyguda, Mateusz, Vega-Peñaloza, Alberto, Dell’Amico, Luca
      Abstract: The synthesis of a set of new organic photocatalysts (PCs) with a donor-acceptor carbazolyl dicyanobenzene structure is reported. The PCs developed have fine-tailored redox potentials from –1.62 V (PC•+/PC*) to 1.36 V (PC*/PC•–) and were accessed through a straightforward two-step synthesis. The potential of these PCs was demonstrated in synthetically relevant reactions with mechanistically opposite thermodynamic requirements, previously reported only in the presence of precious Ir-based PCs. In addition, the PCs outperformed the yields promoted by the well-established 4CzIPN organic dye in both type of reactions.
      Citation: Synthesis ; : -
      PubDate: 2022-02-18T00:00:00+0100
      DOI: 10.1055/a-1776-0929
       
  • Selenium Radical-Triggered Spiro-Tricyclization of
           N-Aryl-N-(2-hydroxyethyl)propiolamides

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      Authors: Pan; Feng, Xie, Huilin, Xie, Wenlin, Wang, Yu-Chao, Liu, Jin-Biao, Qiu, Guanyinsheng
      Abstract: A blue LED-promoted dearomative oxo-spirocyclization of N-aryl-N-(2-hydroxyethyl)propiolamides is developed. The reaction works well to provide a series of selenium-containing benzo[b]pyrrolo[2,1-c][1,4]oxazine-3,9-diones with high efficiency and good tolerance for functional groups. Besides, diselenium-containing benzo[b]pyrrolo[2,1-c][1,4]oxazine-3,9-diones can also be efficiently synthesized in the presence of Oxone. In this process, it is believed that a selenium radical-triggered ipso-cyclization and oxo-Michael addition are involved. Further applications using the prepared products in bioactivity assay is currently underway.
      Citation: Synthesis ; : -
      PubDate: 2022-02-17T00:00:00+0100
      DOI: 10.1055/a-1775-2910
       
  • Asymmetric Total Synthesis of Ventilanones A and B, Two Naturally
           Occurring Pyranonaphthoquinones from Ventilago harmandiana

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      Authors: Deelertpaiboon; Pramchai, Kongsriprapan, Sopanat, Krajangsri, Suppachai, Betterley, Nolan M., Kuhakarn, Chutima, Reutrakul, Vichai
      Abstract: The asymmetric synthesis of the novel pyranonaphthoquinones ventilanone A and ventilanone B, isolated from the Thai endemic plant Ventilago harmandiana, is accomplished by employing l-rhamnose and gallic acid as the starting materials. The key reactions are the utilization of a newly introduced reagent, PhSCF2H/SnCl4, for the formyl­ation of sterically hindered aromatics containing an electron-withdrawing methyl ester, and the efficient Hauser annulation of phenyl­thiophthalides with optically active C-1 glycals derived from l-rhamnose. The developed synthetic methodologies solve the long-standing problem of the formylation of sterically hindered aromatics containing electron-withdrawing groups, and are applicable for the synthesis of other analogues with substituents on the aromatic and pyran rings.
      Citation: Synthesis ; : -
      PubDate: 2022-02-16T00:00:00+0100
      DOI: 10.1055/a-1773-4386
       
  • Survey of New, Small-Molecule Isatin-Based Oxindole Hybrids as
           Multi-Targeted Drugs for the Treatment of Alzheimer’s Disease

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      Authors: Marques; Carolina S., López, Óscar, Leitzbach, Luisa, Fernández-Bolaños, José G., Stark, Holger, Burke, Anthony J.
      Abstract: In the last decade, our group has been very active at developing and assaying complex libraries of scaffolds with a focus on their potential to identify bioactive drug candidates for neurodegenerative diseases, particularly Alzheimer’s disease (AD). Attention has been focused on isatin-based oxindole scaffolds, for which promising results concerning butyrylcholinesterase (BuChE) inhibitory activity have previously been obtained. Considering some published reports and detailed analysis of the pharmacophores of commercially available drugs for AD (powerful cholinesterase (ChE) inhibitors), we performed a strategic structural modification of the isatin core and generated a new family of isatin-based oxindole hybrids (27 new compounds) possessing crucial key functional units in their framework. The syntheses were accomplished using multiple approaches, including simple N-alkylation reactions, copper-catalyzed amination reactions, and click chemistry. The resulting library was evaluated on ChE and MAO enzymes, both of which are involved in the pathophysiology of neurodegeneration. IC50 values of 1.6 and 2.6 μM (BuChE assays), were achieved for the best inhibitors.
      Citation: Synthesis ; : -
      PubDate: 2022-02-16T00:00:00+0100
      DOI: 10.1055/s-0041-1737343
       
  • Convenient Approach to Bicyclic Sultams

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      Authors: Filimonchuk; Sergiy L., Nazarenko, Kostiantyn, Shvydenko, Tetiana, Shvydenko, Kostiantyn, Rusanov, Eduard B., Kostyuk, Aleksandr
      Abstract: A method for the synthesis of aminomethyl-substituted five-membered sultams has been developed. The aminomethyl sultams were synthesized from the corresponding iodomethyl derivatives by nucleophilic substitution of the iodine atom with sodium azide followed by reduction on Pd/C. This method was further expanded to side-chain-substituted sultams, starting from amino acid esters, to obtain aminomethyl-containing bicycles. The simple practical procedure and available starting amino acid esters, including chiral examples, make various bicyclic sultams readily available.
      Citation: Synthesis ; : -
      PubDate: 2022-02-15T00:00:00+0100
      DOI: 10.1055/s-0040-1719894
       
  • Formation of a Naphthalene Framework by Rhodium(III)-Catalyzed Double
           C–H Functionalization of Arenes with Alkynes: Impact of a Supporting
           Ligand and an Acid Additive

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      Authors: Kharitonov; Vladimir B., Muratov, Dmitry V., Nelyubina, Yulia V., Loginov, Dmitry A.
      Abstract: An efficient protocol has been developed for the synthesis of larger condensed arenes from aromatic hydrocarbons and internal alkynes. This protocol uses readily available [CpRhI2]n as a catalyst and Cu(OAc)2 as an oxidant and proceeds smoothly through undirected double C–H activation. The addition of trifluoroacetic acid has a crucial positive impact on the reaction selectivity and the yields of the target products. In contrast to the previously reported catalytic systems, the new conditions allow the use of both dialkyl- and diarylacetylenes with the same high efficiency.
      Citation: Synthesis ; : -
      PubDate: 2022-02-15T00:00:00+0100
      DOI: 10.1055/s-0041-1737342
       
  • Synthesis of Racemic and Enantiopure Forms of β-Carboline Alkaloid
           Brevicolline

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      Authors: Szabó; Tímea, Görür, Funda Lidya, Horváth, Simon, Volk, Balázs, Milen, Mátyás
      Abstract: A new total synthesis of the pharmacologically active β-carboline alkaloid brevicolline is described. The new synthetic approach is based on a commercially available and inexpensive starting material and reagents leading to a practical synthesis of the racemic target molecule, the natural (S)-enantiomer, and its antipode. Initially, the construction of the β-carboline skeleton and functionalization at the C(4) position have been accomplished. The formation of dihydropyrrole structural unit was obtained as the result of an Au-catalyzed hydroamination reaction, which was followed by a reduction that led to the chiral intermediate. The synthetic route described here is developed to ensure the sustainable access of the racemic brevicolline in 11 steps with improved 48% overall yield compared to the previously reported methods.
      Citation: Synthesis ; : -
      PubDate: 2022-02-15T00:00:00+0100
      DOI: 10.1055/s-0041-1737830
       
  • Stereoselective Domino Reactions in the Synthesis of Spiro Compounds

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      Authors: Westphal; Regina, Venturini Filho, Eclair, Medici, Fabrizio, Benaglia, Maurizio, Greco, Sandro J.
      Abstract: This review summarizes the latest developments in asymmetric domino reactions, with the emphasis on the preparation of spiro compounds. Discussions on the stereoselectivity of the transformations, the reaction mechanisms, the rationalization of the stereochemical outcome, and the applications of domino reactions to the synthesis of biologically active molecules and natural products are included when appropriate.1 Introduction2 Asymmetric Domino Reactions2.1 Domino Reactions Initiated by Michael Reactions2.2 Domino Reactions Initiated by Mannich Reactions2.3 Domino Reactions Initiated by Knoevenagel Reactions2.4 Domino Reactions Initiated by Cycloaddition Reactions2.5 Domino Reactions Initiated by Metal Insertion2.6 Other Mechanisms3 Conclusion
      Citation: Synthesis ; : -
      PubDate: 2022-02-14T00:00:00+0100
      DOI: 10.1055/a-1771-0641
       
  • Palladium-Catalyzed Cyanation of Arenediazonium Tetrafluoroborate
           Derivatives with 2-(Piperidin-1-yl)acetonitrile as the Cyano Source

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      Authors: Ahmad; Muhammad Siddique, Shafiq, Zahid, Meguellati, Kamel
      Abstract: The present study describes the one-pot palladium-catalyzed cyanation of commercially available aryldiazonium tetrafluoroborate derivatives with 2-(piperidin-1-yl)acetonitrile (an organic cyano reagent) under mild conditions. This process utilizes a Pd/(Me3Si)2 system and is applied to a wide scope of aromatic diazonium substrates to give the corresponding nitrile-containing products in moderate to high yields (59–92%). This methodology is employed for the preparation of etravirine, a drug used for the treatment of HIV, and for transformations of 1H-indole-2-carbonitrile into compounds that are used as a NMDA receptor antagonists and that have high potential against mutant HIV strains. The mechanism proposed for this Pd-catalyzed cyanation involves cyanide ions, as confirmed using indicator paper.
      Citation: Synthesis ; : -
      PubDate: 2022-02-14T00:00:00+0100
      DOI: 10.1055/a-1770-8592
       
  • Synthetic Studies on Chromone Natural Products: The Preusso­chromones

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      Authors: Beller; Marc Paul, Koert, Ulrich
      Abstract: Total syntheses of preussochromones A, D, E, and F and structural revisions of preussochromones E and F are reviewed, demonstrating the use of α-keto esters and α,β-diketo esters as valuable reactants in stereoselective cyclization reactions in total synthesis.1 Introduction2 The Route to Preussochromone D3 Synthesis and Structural Revision of Preussochromones E and F4 Total Synthesis of Preussochromone A5 Conclusion
      Citation: Synthesis ; : -
      PubDate: 2022-02-14T00:00:00+0100
      DOI: 10.1055/a-1771-3564
       
  • Synthesis of Structurally Defined Nitroxide Spin-Labeled Glycolipids as
           Useful Probes for Electron Paramagnetic Resonance (EPR) Spectroscopy
           Studies of Cell Surface Glycans

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      Authors: Yan; Xin, Guo, Zhongwu
      Abstract: Four glycolipids carrying different glycans and a nitroxide free radical spin at the glycan non-reducing end were designed and synthesized from free glucose and maltooligosaccharides by an efficient and streamlined synthetic strategy. The main features of this synthetic strategy include regioselective functionalization of the free carbohydrates and coupling of the radical spin label with functionalized free glycans as the last synthetic step. These glycolipids are useful probes for the study of cell surface glycans by electron paramagnetic resonance spectroscopy. Moreover, the key synthetic intermediates, free glycolipids carrying a flexible azido group at the glycan non-reducing end, are widely useful platforms for accessing glycolipids with other molecular labels.
      Citation: Synthesis ; : -
      PubDate: 2022-02-10T00:00:00+0100
      DOI: 10.1055/a-1768-2138
       
  • Concise Synthesis of (S)-7-Hydroxy-5-aza-8a-epi-d-swainsonine from a
           d-Erythrose Derivative

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      Authors: Sousa; Cristina E. A., Salgueiro, Daniela A. L., Alves, Maria J.
      Abstract: A five-step synthesis of (S)-7-hydroxy-5-aza-8a-epi-d-swainsonine [(3S,4S,4aS,5S,6R)-octahydropyrrolo[1,2-b]pyridazine-3,4,5,6-tetraol] was accessed in good overall yield from readily available d-erythrosyl benzylidene acetal buta-1,3-diene. The key step of the reaction sequence is a full stereoselective Diels–Alder cycloaddition between­ the diene and dienophile: diethyl azodicarboxylate (DEAD) or di-tert-butyl azodicarboxylate (DBAD). The cycloadducts were further transformed into the title 5-aza-indolizidine. Optimized procedures were obtained for the synthesis of intermediates and products.
      Citation: Synthesis ; : -
      PubDate: 2022-02-10T00:00:00+0100
      DOI: 10.1055/a-1768-2082
       
  • Generation of Thiyl Radicals from Air-Stable, Odorless Thiophenol
           Surrogates: Application to Visible-Light-Promoted C–S Cross-Coupling

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      Authors: Swan; Charlie, Maggi, Lorenzo, Park, Mahri, Taylor, Sophie, Shepherd, William, Ball, Liam T.
      Abstract: The synthetic versatility of thiophenols is offset by their air-sensitivity and foul odor. It is demonstrated that S-aryl isothiouronium salts can be used as precursors to thiyl radicals, extending the practical benefits of these air-stable, odorless salts from ionic to single electron manifolds. The isothiouronium salts are accessed via Ni-catalyzed cross-coupling of (hetero)aryl iodides and thiourea and are isolated as free-flowing solids following anion exchange. Judicious choice of a redox-innocent counteranion enables use of these convenient thiophenol surrogates in radical processes, as is exemplified by the synthesis of non-symmetrical diaryl thioethers via light-promoted S-arylation.
      Citation: Synthesis ; : -
      PubDate: 2022-02-10T00:00:00+0100
      DOI: 10.1055/s-0041-1737816
       
  • Ferrocenephosphonates: Copper-Promoted Synthesis and Further
           Functionalization

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      Authors: Abaid; Kmar, Erb, William, Blot, Marielle, Roisnel, Thierry, Mongin, Florence, Touil, Soufiane
      Abstract: Ferrocenephosphonates make up an important class of organometallic derivatives with a wide range of useful applications in organic synthesis and coordination chemistry. Here, an approach to ferrocenephosphonates based on a copper-promoted Hirao coupling is reported. Further functionalizations based on regioselective deprotolithiation and both Negishi and Suzuki–Miyaura cross-coupling reactions are also described to reach original derivatives.
      Citation: Synthesis ; : -
      PubDate: 2022-02-09T00:00:00+0100
      DOI: 10.1055/a-1767-3026
       
  • Cinchona Alkaloid Catalyzed Dynamic Kinetic Resolution of Biaryl Aldehydes
           via Asymmetric Decarboxylative Transamination

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      Authors: Guo; Donghui, Wang, Jian
      Abstract: An unprecedented Cinchona alkaloid catalyzed atropoenantioselective transamination of biaryl aldehydes with 2,2-diphenylglycine via a cascade decarboxylation and dynamic kinetic resolution strategy is described. This protocol features broad substrate scope and good functional group tolerance and allows the rapid assembly of axially chiral biaryls in high yields with acceptable to good enantioselectivities. In addition, such structural motifs may have potential applications in enantioselective catalysis as chiral ligands or catalysts.
      Citation: Synthesis ; : -
      PubDate: 2022-02-09T00:00:00+0100
      DOI: 10.1055/a-1767-6153
       
  • Application of Proline-Derived (Thio)squaramide Organocatalysts in
           Asymmetric Diels–Alder and Conjugate Addition Reactions

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      Authors: Dargó; Gyula, Nagy, Sándor, Kis, Dávid, Bagi, Péter, Mátravölgyi, Béla, Tóth, Blanka, Huszthy, Péter, Drahos, László, Kupai, József
      Abstract: The synthesis of chiral proline-derived squaramide and thiosquaramide organocatalysts, which are capable of the dual activation in asymmetric reactions is reported. The (thio)squaramide moiety can form hydrogen bonds to activate the substrates and to stereocontrol the reaction, while the pyrrolidine unit can form enamines to activate carbonyl compounds via aminocatalysis. Comparing the performance of thiosquaramide to squaramide, the Diels–Alder reaction of (anthracen-9-yl)acetaldehyde and trans-β-nitrostyrene was examined, which has been investigated in the literature using quantum chemical calculations. Both squaramide and thiosquaramide gave excellent yields (up to 99%) and enantiomeric excess values (up to 98%). Moreover, their catalytic performance was compared in conjugate addition of lawsone to β,γ-unsaturated α-keto ester.
      Citation: Synthesis ; : -
      PubDate: 2022-02-09T00:00:00+0100
      DOI: 10.1055/s-0040-1719886
       
  • Functionalized d- and l-Arabino-Pyrrolidines as Potent and Selective
           Glycosidase Inhibitors

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      Authors: Haarr; Marianne B., Lopéz, Óscar, Fernández-Bolaños, Jóse G., Lindbäck, Emil, Sydnes, Magne O.
      Abstract: The efficient synthesis of enantiomeric pairs of iminosugars including 1,4-dideoxy-1,4-imino-d-arabinitol (DAB) and 1,4-dideoxy-1,4-imino-l-arabinitol (LAB) analogues with an amidine, hydrazide, hydrazide imide, or amide oxime moiety is described. The preparation of DAB and LAB analogues commenced from l-xylose and d-xylose, respectively. The obtained iminosugars are tested against a panel of glycosidases with pharmaceutical relevance, revealing enhanced activity for the DAB analogues in comparison with the LAB analogues. In particular, the d-arabino-configured amidine behaved as a potent (submicromolar range) and selective inhibitor of α-mannosidase.
      Citation: Synthesis ; : -
      PubDate: 2022-02-07T00:00:00+0100
      DOI: 10.1055/a-1764-8950
       
  • From Ring-Expansion to Ring-Contraction: Synthesis of γ-Lactones from
           Cyclobutanols and Relative Stability of Five- and Six-Membered
           Endoperoxides toward Organic Bases

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      Authors: Jamey; Nicolas, Ferrié, Laurent
      Abstract: Cyclobutanols undergo ring expansion with molecular oxygen in the presence of Co(acac)2 to afford 1,2-dioxane-hemiperoxyketals. In the course of acylation, we observed that endoperoxides rearranged into γ-lactone in the presence of triethylamine. Thus, a generalization of this ring contraction through a Kornblum–DeLaMare rearrangement is here reported. Application of this transformation to monosubstituted 1,2-dioxane derivatives also led to 1,4-ketoaldehydes, in proportions depending on the nature of the substituent. These same conditions applied to five-membered dioxolane analogues led to fragmentation instead, through a retro-aldol type process. This study emphasizes the difference of stability of 1,2-dioxane and 1,2-dioxolane against organic bases, 1,2-dioxolanes having proved to be particularly reactive whereas 1,2-dioxanes showed a relative tolerance under these conditions.
      Citation: Synthesis ; : -
      PubDate: 2022-02-07T00:00:00+0100
      DOI: 10.1055/a-1765-1615
       
  • Towards Tianeptine Analogues: Synthesis of New Ring Systems Containing a
           Dibenzo[c,f][1,2]thiazepine S,S-Dioxide Core

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      Authors: Berecz; Gábor, Dancsó, András, Németh, Dóra R., Kiss, Loránd, Simig, Gyula, Volk, Balázs
      Abstract: In the course of the synthesis of fused-ring analogues of the antidepressant drug tianeptine, representatives of three new heterocyclic ring systems, indolo[1,7-bc][1,2]benzothiazepines (and their 4,5-dihydro analogues), 5,6-dihydroquino[1,8-bc][1,2]benzothiazepines, and [1,2]benzothiazepino[4,3,2-jk]carbazoles, as well as their intermediates, have been prepared. The tetracyclic and pentacyclic ring systems containing either an oxo or a hydroxy functional group are suitable for introducing various side chains, including potential pharmacophores. For this latter transformation, examples are demonstrated by conversion of the hydroxy group into a chloro moiety and subsequent reaction with amines or with primary alcohols bearing a tertiary amino side chain. Two fused-ring derivatives exhibiting the side-chain characteristics of tianeptine have also been synthesized. Altogether 40 compounds are described in the present manuscript, eight of them are also characterized by single-crystal X-ray diffraction.
      Citation: Synthesis ; : -
      PubDate: 2022-02-07T00:00:00+0100
      DOI: 10.1055/s-0040-1719885
       
  • Beyond the Bioorthogonal Inverse-Electron-Demand Diels–Alder Reactions
           of Tetrazines: 2-Pyrone-Functionalized Fluorogenic Probes

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      Authors: Cserép; Gergely B., Németh, Krisztina, Szatmári, Ágnes, Horváth, Flóra, Imre, Tímea, Németh, Krisztina, Kele, Péter
      Abstract: The applicability of pyrones as a bioorthogonal platform was explored in inverse-electron-demand Diels–Alder (IEDDA) reactions with a strained cyclooctyne. Studies showed that the pyrones are indeed suitable for IEDDA reactions under physiological conditions. Furthermore, the stable pyrone moiety could be utilized to construct easily accessible fluorogenic probes. Mutual orthogonality of the IEDDA reaction of 2-pyrones with SPAAC reactions of azides was also explored.
      Citation: Synthesis ; : -
      PubDate: 2022-02-04T00:00:00+0100
      DOI: 10.1055/a-1761-4672
       
  • Chiral Calcium Phosphate Catalyzed Enantioselective Synthesis of
           All-Carbon Quaternary Center by Friedel–Crafts Alkylation Reaction of
           Pyrroles and Trifluoromethylated Nitrostyrenes

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      Authors: Uchikura; Tatsuhiro, Yokohama, Sosuke, Murakami, Mona, Akiyama, Takahiko
      Abstract: A chiral calcium phosphate-catalyzed enantioselective Friedel–Crafts alkylation reaction of pyrroles and α-trifluoromethyl-β-nitrostyrenes has been developed. Pyrroles bearing an all-carbon quaternary center at 2-position were obtained with high to excellent enantioselectivity. Use of 4,7-dihydroindole as a nucleophile and subsequent oxidation resulted in the formation a 2-substituted indole derivative with excellent enantioselectivity. A 3,4-dihydropyrrolo[1,2-c]pyrimidine derivative was successfully synthesized by reduction followed by benzoylation of the product without loss of enantioselectivity. Application to a 1 mmol scale reaction was successfully achieved.
      Citation: Synthesis ; : -
      PubDate: 2022-02-04T00:00:00+0100
      DOI: 10.1055/s-0040-1719879
       
  • Dual Role of the Arylating Agent in a Highly C(2)-Selective Pd-Catalysed
           Functionalisation of Pyrrole Derivatives

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      Authors: Petkovic; Milos, Jovanovic, Milos, Jovanovic, Predrag, Simic, Milena, Tasic, Gordana, Savic, Vladimir
      Abstract: Pyrrole derivatives with C(2)-aryl substituents are an important and widespread class of heterocyclic compounds. Their synthesis can be accomplished using several strategic variants which usually entail either protection of the N–H functionality followed by the arylation, or a direct arylation. Although direct arylation is a preferable process due to a reduced number of synthetic steps, it often requires vigorous conditions or challenging reagents. To this synthetic repertoire, we add a novel method that is based on the dual role of the arylating agent. It serves as the nitrogen protecting group while also being involved in the arylation step. Deprotection as a final stage is carried out simultaneously utilising amines as reacting components. This approach ensures relatively mild conditions and exclusive C(2) selectivity yielding 2-arylpyrroles with the amide functionality. While aromatic amines are not suitable partners under studied conditions, most likely due to lower nucleophilicity, aliphatic amines, either primary or secondary, afford products in good yields.
      Citation: Synthesis ; : -
      PubDate: 2022-02-02T00:00:00+0100
      DOI: 10.1055/a-1758-6312
       
  • Forging C–C Bonds through Intramolecular Oxidative Coupling of
           Organoborates – An Overview

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      Authors: Didier; Dorian
      Abstract: C–C bond formation has challenged the community of synthetic organic chemists for decades. Organoboron derivatives represent a mild and functional-group-tolerant class of reagents that can be handled without the need for inert conditions, making them suitable scaffolds for the development of methods that increase the sustainability of current processes for coupling reactions. This short review summarizes the different approaches that have been developed to enable C–C bond formation through intramolecular rearrangements of organoborate species.1 Introduction2 Oxidative Coupling with Chemical Oxidants3 Electrocoupling of Tetraorganoborates4 Photocoupling of Tetraorganoborates
      Citation: Synthesis ; : -
      PubDate: 2022-02-01T00:00:00+0100
      DOI: 10.1055/a-1757-2680
       
  • Iridium-Catalyzed Acceptorless Dehydrogenative Coupling of
           2-Aminoarylmethanols with Amides or Nitriles to Synthesize Quinazolines

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      Authors: Shui; Hongling, Zhong, Yuhong, Ouyang, Lu, Luo, Nianhua, Luo, Renshi
      Abstract: An efficient iridium-catalyzed acceptorless dehydrogenative coupling (ADC) reaction for the preparation of various quinazolines from 2-aminoarylmethanols and amides or nitriles had been developed. A wide range of substituted 2-aminobenzyl alcohols and (hetero)aryl or alkyl benzamides and nitriles were well compatible to afford various quinazolines in excellent yields. Merits of this new strategy are the high atom-economy, mild reaction conditions, and simple operation, and the methodology is suitable for a variety of substrates.
      Citation: Synthesis ; : -
      PubDate: 2022-01-31T00:00:00+0100
      DOI: 10.1055/a-1755-4700
       
  • C(sp3)–F Bond Transformation of Perfluoroalkyl Compounds Mediated by
           Visible-Light Photocatalysis: Spin-Center Shifts and Radical/Polar
           Crossover Processes via Anionic Intermediates

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      Authors: Nishimoto; Yoshihiro, Sugihara, Naoki, Yasuda, Makoto
      Abstract: Due to its large bond energy, precisely controllable C–F bond activation is a significant challenge in organic synthesis. A single C(sp3)–F bond transformation of perfluoroalkyl groups is particularly desirable to supply functionalized perfluoroalkyl compounds offering properties that are potentially useful in pharmaceutical and materials chemistry. Recently, the single defluorinative transformation of perfluoroalkyl compounds has been developed via visible-light photocatalysis. Herein, we summarize this field via two main topics. Topic 1 covers the transformations of C(sp3)–F bonds in either perfluoroalkylarenes or perfluoroalkane carbonyl compounds via a defluorinative spin-center shift in the radical anion intermediates. Topic 2 addresses the defluorinative transformations of α-trifluoromethyl alkenes to give gem-difluoroalkenes via a radical/polar crossover process.1 Introduction2 C(sp3)–F Transformations via Defluorinative Spin-Center Shifts3 C(sp3)–F Transformations via a Radical/Polar Crossover Process4 Conclusions
      Citation: Synthesis ; : -
      PubDate: 2022-01-31T00:00:00+0100
      DOI: 10.1055/a-1755-3476
       
  • Synthetic Approaches for the Construction of Five- and Six-Membered
           Silaazacycles

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      Authors: Wang; Wanshu, Gao, Lu, Song, Zhenlei
      Abstract: Silaazacycles (or azasilacycles), containing both nitrogen and silicon atoms, are appealing ring structures in the development of silicon-containing functional molecules. The development of general and efficient methods towards these motifs has therefore attracted considerable attention from synthetic chemists. This short review intends to highlight representative advances in the synthesis of five- and six-membered silaazacycles.1 Introduction2 Five-Membered Silaazacycles2.1 Five-Membered Silaazacycles bearing a 1,2-N/Si Moiety2.2 Five-Membered Silaazacycles bearing a 1,3-N/Si Moiety3 Six-Membered Silaazacycles3.1 Six-Membered Silaazacycles bearing a 1,2-N/Si Moiety3.2 Six-Membered Silaazacycles bearing a 1,3-N/Si Moiety3.3 Six-Membered Silaazacycles bearing a 1,4-N/Si Moiety4 Conclusion
      Citation: Synthesis ; : -
      PubDate: 2022-01-31T00:00:00+0100
      DOI: 10.1055/a-1755-3832
       
  • Stereoselective Synthesis of Cyclohexane Derivatives: Tandem Lithium
           Iodide Mediated Intramolecular Conjugate Addition of Thiols to
           α,β-Bisenones

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      Authors: Jeon; Minseok, Yun, Chaeyoung, Seo, SungYong
      Abstract: A tandem intramolecular conjugate addition reaction was conducted with α,β-bisenones as selected Michael acceptors which were converted into 1,2,3-trisubstituted six-membered rings in the presence of activated sulfur nucleophiles. The products were obtained in good to excellent yields (maximum yield: 99%). Various substituted α,β-bisenones and sulfur nucleophiles were examined to understand the substrate scope of the reaction. Only one diastereomer was isolated, as lithium iodide mediated enolate trapping reactions improve the stereoselectivity of reactions involving 1,2,3-trisubstituted cyclohexanes.
      Citation: Synthesis ; : -
      PubDate: 2022-01-28T00:00:00+0100
      DOI: 10.1055/a-1754-7424
       
  • Taking the Green Road Towards Pharmaceutical Manufacturing

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      Authors: Federsel; Hans-Jürgen
      Abstract: The introduction of the Green Chemistry Principles in the late 1990s formed the basis for a transition to a greener environment. These Principles have become an integral part in the work on designing chemical processes, especially for large-scale manufacture. The ultimate target is the achievement of a sustainable production method allowing hundreds of tons of valuable materials to be prepared. For this purpose, a holistic view must be applied to the elements constituting a fully-fledged process encompassing layout of the synthetic route, defining starting materials and their origin, output of product and quality features, quantity of effluent streams and waste, recovery and recycling of chemicals involved, and energy consumption. These parameters form a complex matrix where the individual components are in a complicated relationship with each other. This short review addresses these issues and the benefits of life-cycle assessment and metrics commonly used to measure the performance of chemical manufacturing – all from a pharmaceutical industry perspective as experienced by the author.1 Introduction: Facing Severe Challenges2 The Historical Context: Addressing an Image Problem3 Prospects, Drivers and Roadmap for the Green Future4 Living by the Principles: Industrial Perspectives5 Taking the Green Route – Catalysis Leading the Way: Case Stories6 State of the Art: How Green Are We'7 Sending Signals, Creating Impressions: Focus on Communication8 Conclusions
      Citation: Synthesis ; : -
      PubDate: 2022-01-27T00:00:00+0100
      DOI: 10.1055/a-1752-5471
       
  • 4-(tert-Butyldiphenylsilyloxy)-2,2-dimethylbutanoyl: An Easily Removable
           Pivaloyl-Type Protecting Group with High Orthogonality

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      Authors: Li; Qishuai, Su, Yong, Qiao, Zhi, Wang, Jianjun, Wang, Peng, Ren, Sumei, Song, Ni, Li, Ming
      Abstract: Protecting groups play multiple and vital roles during the synthesis of carbohydrates and other natural products. We herein report the installation and orthogonal cleavage, under mild conditions, of a 4-(tert-butyldiphenylsilyloxy)-2,2-dimethylbutanoyl (BDMB) group as a sterically hindered pivaloyl-type hydroxy protecting group. The compatibility of this substituent with the removal of other protecting groups is also investigated. Due to its advantageous properties, BDMB is anticipated to function as a valuable agent for masking hydroxy groups.
      Citation: Synthesis ; : -
      PubDate: 2022-01-26T00:00:00+0100
      DOI: 10.1055/a-1751-1225
       
  • A General Way to Spiro-Annulated 2-Benzoxepines via Rh2(esp)2-Catalyzed
           [5+2] Cycloaddition of Diazo Arylidene Succinimides to Ketones

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      Authors: Vepreva; Anastasia, Kantin, Grigory, Krasavin, Mikhail, Dar’in, Dmitry
      Abstract: The formation of spirocyclic 2-benzoxepines by Rh2(esp)2-catalyzed decomposition of diazo arylidene succinimides in the presence of ketones was investigated. This transformation, which is a formal [5+2] cycloaddition of styryl rhodium carbenes to the carbonyl group, occurs in high yields under mild conditions, with high carbonyl substrate tolerance and diastereoselectivity. The developed general method opens access to rare spiro (hetero)cyclic scaffolds with great potential in drug discovery.
      Citation: Synthesis ; : -
      PubDate: 2022-01-26T00:00:00+0100
      DOI: 10.1055/s-0037-1610790
       
  • Dehydrative and Decarboxylative Coupling of Alkynoic Acids with Allylic
           Alcohols

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      Authors: Qiu; Ju, Hou, Jingwei, Sun, Zuolian, Xie, Peizhong
      Abstract: A direct dehydroxylative and decarboxylative coupling between a large number of allylic alcohols and alkynoic acids was realized affording 1,4-enyne motifs in high efficiency. In this reaction, calcium-promoted C–OH bond cleavage was crucial, which facilitated the sequential ­decarboxylation, and thus enabled the palladium-catalyzed allyl­–alkynyl coupling, which occurred in an environmentally benign manner tolerating a wide variety of functional groups. This protocol has been successfully used in preparing anticancer active rooperol derivatives in gram scale.
      Citation: Synthesis ; : -
      PubDate: 2022-01-25T00:00:00+0100
      DOI: 10.1055/a-1750-3080
       
  • Recent Advances in Construction of C(sp2)–O Bonds via Aryne Participated
           Multicomponent Coupling Reactions

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      Authors: Zhang; Ruirui, Peng, Xia, Tan, Jiajing
      Abstract: Aryne chemistry is a powerful synthetic technique that forms new bonds to aromatic rings. The recent resurgence of aryne-based multicomponent coupling strategies has led to an influx of methodologies for the mild synthesis of arene derivatives. In particular, these innovative discoveries broaden and streamline approaches toward phenol ether motifs, which are a prevalent structural component across a broad range of chemistry related research fields. Herein, this review aims to provide a comprehensive overview of the recent progress in the construction of C(sp2)–O bonds via aryne-induced multicomponent reactions. Special attention has been paid to reaction design and mechanistic pathways.1 Introduction2 Insertion-Based MCRs3 Nucleophilic-Addition-Based MCRs4 Cycloaddition-Based MCRs5 Summary
      Citation: Synthesis ; : -
      PubDate: 2022-01-24T00:00:00+0100
      DOI: 10.1055/a-1748-7448
       
  • Base/B2pin2-Mediated Iodofluoroalkylation of Alkynes and Alkenes

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      Authors: Wu; Jianglong, Wang, Chenyu, Wang, Zhongjie, Li, Hongjun, Liu, Ruyan, Wang, Yan, Zhou, Pengsheng, Li, Dianjun, Yang, Jinhui
      Abstract: A base/B2pin2-mediated iodofluoroalkylation of alkynes and a part of alkenes, using ethyl difluoroiodoacetate (ICF2CO2Et) or ICnF2n+1 (n = 3, 4, 6) as difluoroacetylating or perfluoroalkylating reagent, is disclosed. The reaction proceeds under mild conditions, and iododifluoroalkylation, hydrodifluoroalkylation and several perfluoroalkylation products were generated from alkynes or alkenes. Notably, this methodology provides a simple access to difluoroalkylated and perfluoroalkylated organic compounds starting from simple alkynes or alkenes.
      Citation: Synthesis ; : -
      PubDate: 2022-01-21T00:00:00+0100
      DOI: 10.1055/a-1747-5457
       
  • Ru(II)-Catalyzed C–H Activation and Alkyne Annulation Reaction of Phenyl
           Indandiones: Synthesis of Spirobi[indene]diones

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      Authors: Bora; Bidisha R., Sultana, Sabera, Sarma, Bipul, Gogoi, Sanjib
      Abstract: A Ru(II)-catalyzed synthesis of spirobi[indene]dione from phenyl indandione and alkyne is reported. This metal-catalyzed cyclization reaction proceeds through hydroxy group directed C(sp2)–H bond activation, keto–enol tautomerization and alkyne annulation pathways.
      Citation: Synthesis ; : -
      PubDate: 2022-01-17T00:00:00+0100
      DOI: 10.1055/a-1743-0191
       
  • Electrocyclization and Unexpected Reactions of Non-Stabilized
           α,β:γ,δ-Unsaturated Azomethine Ylides: Experimental and Theoretical
           Studies

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      Authors: Molnár; István G., Mucsi, Zoltán, Kovács, Ervin, Nyerges, Miklós
      Abstract: Versatile, two-step syntheses of dihydrodibenzo[c,e]azepines, carbazole derivatives, and other alkaloid-type drug-like scaffolds by in situ generated azomethine ylide-induced intramolecular electrocyclization reaction from commercially available materials are presented. The reaction mechanisms of transition-metal-free carbon–carbon bond formation and the role of the kinetic control, resulting in the good regioselectivity, were confirmed by theoretical calculations.
      Citation: Synthesis ; : -
      PubDate: 2022-01-17T00:00:00+0100
      DOI: 10.1055/a-1742-2005
       
  • Impact of Design of Experiments in the Optimisation of Catalytic Reactions
           in Academia

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      Authors: Nori; Valeria, Sinibaldi, Arianna, Pesciaioli, Fabio, Carlone, Armando
      Abstract: Design of Experiments (DoE) is extensively and routinely used in industry; however, in recent decades, it has gained increasing interest from academia in organic synthesis. The use of chemometrics is an attractive strategy to find the real optimum in chemical reactions, especially when affected by several variables. DoE has been applied in a growing number of synthetic transformations over the years, where it undoubtedly helps in the process of optimisation, saving costs and time. This review concisely discusses the chemometric basis of Design of Experiments and highlights several examples in which DoE is applied in organic synthesis.1 Introduction2 Chemometric Basis of DoE3 DoE Applied in Catalysis: Selected Examples3.1 DoE in Metal Catalysis3.2 DoE in Biocatalysis3.3 DoE in Organocatalysis4 Conclusions
      Citation: Synthesis ; : -
      PubDate: 2022-01-11T00:00:00+0100
      DOI: 10.1055/a-1736-6703
       
  • Elucidation of the Nucleophilic Potential of Diazocyclopentadiene

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      Authors: Hartnagel; Manfred, Ofial, Armin R., Mayr, Herbert
      Abstract: Diazocyclopentadiene reacts with benzhydrylium ions (Ar2CH+) to give 2,5-dibenzhydryl-substituted diazocyclopentadienes. The kinetics have been determined photometrically in dichloromethane under pseudo-first-order conditions using diazocyclopentadiene in excess. Plots of the second-order rate constants (log k 2) versus the electrophilicity parameters E of the benzhydrylium ions gave the nucleo­philicity parameter N = 4.84 and susceptibility s N = 1.06 for diazo­cyclopentadiene according to the correlation log k(20 °C) = s N(E + N). Diazocyclopentadiene thus has a similar nucleophilic reactivity as pyrrole. Previously reported electrophilic substitutions of diazocyclopentadiene are rationalized by these parameters and new reaction possibilities are predicted.
      Citation: Synthesis ; : -
      PubDate: 2022-01-05T00:00:00+0100
      DOI: 10.1055/s-0041-1737327
       
  • Mimicking Enzymes: Taking Advantage of the Substrate-Recognition
           Properties of Metalloporphyrins in Supramolecular Catalysis

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      Authors: Abuhafez; Naba, Perennes, Antoine, Gramage-Doria, Rafael
      Abstract: The present review describes the most relevant advances dealing with supramolecular catalysis in which metalloporphyrins are employed as substrate-recognition sites in the second coordination sphere of the catalyst. The kinetically labile interaction between metallo­porphyrins (typically, those derived from zinc) and nitrogen- or oxygen-containing substrates is energetically comparable to the non-covalent interactions (i.e., hydrogen bonding) found in enzymes enabling substrate preorganization. Much inspired from host–guest phenomena, the catalytic systems described in this account display unique activities, selectivities and action modes that are difficult to reach by applying purely covalent strategies.
      Citation: Synthesis ; : -
      PubDate: 2022-01-03T00:00:00+0100
      DOI: 10.1055/a-1729-9223
       
  • Synthesis of Alicyclic 2-Methylenethiazolo[2,3-b]quinazolinone Derivatives
           via Base-Promoted Cascade Reactions

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      Authors: El Haimer; Mohamed, Faragó, Tünde, Schelz, Zsuzsanna, Zupkó, István, Palkó, Márta
      Abstract: The synthesis of alicyclic 2-methylenethiazolo[2,3-b]quinazo­l­inones is performed via base-promoted cascade reactions, starting from either alicyclic β-amino propargylamides using carbon disulfide, or from alicyclic ethyl 2-isothiocyanatocarboxylates by addition of propargylamine. In both cases the cascade reaction proceeds by way of a favoured 5-exo-dig process during the second ring closure, as confirmed by full NMR spectroscopic assignments. Moreover, a high-yielding retro­-Diels–Alder (RDA) reaction is performed on the norbornene derivatives leading to 2-methylene-2H-thiazolo[3,2-a]pyrimidin-5(3H)-ones. The obtained compounds exert modest antiproliferative activities against a panel of human gynaecological cancer cell lines.
      Citation: Synthesis ; : -
      PubDate: 2021-12-07T00:00:00+0100
      DOI: 10.1055/s-0040-1720028
       
  • Recent Trends in Group 9 Catalyzed C–H Borylation Reactions: Different
           Strategies To Control Site-, Regio-, and Stereoselectivity

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      Authors: Veth; Lukas, Grab, Hanusch A., Dydio, Paweł
      Abstract: Organoboron compounds continue contributing substantially to advances in organic chemistry with their increasing role as both synthetic intermediates and target compounds for medicinal chemistry. Particularly attractive methods for their synthesis are based on the direct borylation of C–H bonds of available starting materials since no additional pre-functionalization steps are required. However, due to the high abundance of C–H bonds with similar reactivity in organic molecules, synthetically useful C–H borylation protocols demand sophisticated strategies to achieve high regio- and stereoselectivity. For this purpose, selective transition-metal-based catalysts have been developed, with group 9 centered catalysts being among the most commonly utilized. Recently, a multitude of diverse strategies has been developed to push the boundaries of C–H borylation reactions with respect to their regio- and enantioselectivity. Herein, we provide an overview of approaches for the C–H borylation of arenes, alkenes, and alkanes based on group 9 centered catalysts with a focus on the recent literature. Lastly, an outlook is given to assess the future potential of the field.1 Introduction1.1 Mechanistic Considerations1.2 Selectivity Issues in C–H Borylation1.3 Different Modes of Action Employing Directing Group Strategies in C–H Borylation1.4 Scope and Aim of this Short Review2 Trends in C–H Borylation Reactions2.1 Photoinduced Catalysis2.2 Transfer C–H Borylation2.3 Lewis Acid Mediated C–H Borylation2.4 Directed Metalation2.5 Miscellaneous C–H Borylation Reactions2.6 Electrostatic Interactions2.7 Hydrogen Bonding3 Conclusion and Outlook
      Citation: Synthesis ; : -
      PubDate: 2021-12-02T00:00:00+0100
      DOI: 10.1055/a-1711-5889
       
  • Hirao Cross-Coupling Reaction as an Efficient Tool to Build Non-natural
           C2-Phosphonylated Sugars

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      Authors: Monasson; Olivier, Malinowski, Maciej, Lubin-Germain, Nadège, Ferry, Angélique
      Abstract: A range of C2-phosphonylated sugars have been accessed through a palladium-catalyzed Hirao cross-coupling on 2-iodoglycals using trialkylphosphites as phosphorylating reagents. The developed conditions led to the creation of an unnatural C–P bond on sugars and proved to be compatible with diversely protected glycals (acetyl-, benzyl-, PMB-protected) as well as with unprotected substrates. Several monosaccharides and one disaccharide have been synthesized by applying this methodology. Deprotection conditions are also described.
      Citation: Synthesis ; : -
      PubDate: 2021-11-30T00:00:00+0100
      DOI: 10.1055/a-1709-3305
       
  • Applications of Photoredox Catalysis for the Radical-Induced Cleavage of
           C–C Bonds

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      Authors: Vanderghinste; Jaro, Das, Shoubhik
      Abstract: Selective cleavage of C–C bonds forms one of the greatest challenges in current organic chemistry, due to the relative strength of these bonds. However, such transformations are an invaluable instrument to break down and construct new carbon–carbon bonds. To achieve this, photochemistry can be used as a tool to generate radicals and induce the cleavage of these bonds due to their high reactivity. This review examines some of the most influential contributions in this field since 2010.1 Introduction2 C–C Bond Cleavage2.1 Homogeneous Catalyst2.1.1 N-Centered Radical2.2.2 O-Centered Radical2.2 Heterogeneous Catalyst3 C=C Bond Cleavage3.1 Homogeneous Catalyst3.2 Heterogeneous Catalyst4 C≡C Bond Cleavage4.1 Homogeneous Catalyst4.2 Heterogeneous Catalyst5 Conclusion
      Citation: Synthesis ; : -
      PubDate: 2021-11-22T00:00:00+0100
      DOI: 10.1055/a-1702-6193
       
  • Stereoselective Total Synthesis of (+)-Brevipolide H from d-Galactal

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      Authors: Zhao; Ziyang, Lv, Qingwei, Geng, Jialin, Liu, Yang, Hu, Chao, Du, Yuguo, Liu, Jun
      Abstract: An efficient and concise synthesis of cytotoxic 5,6-dihydro-α-pyrone (+)-brevipolide H has been accomplished in 12 long linear steps in 8.65% overall yield from readily available chiral synthons, d-galactal and ethyl l-lactate. The features of this synthesis are highly diastereoselective Simmons–Smith cyclopropanation and carbohydrate-based chiron approach to rapid access to key 5,6-dihydro-α-pyrone skeleton.
      Citation: Synthesis ; : -
      PubDate: 2021-11-17T00:00:00+0100
      DOI: 10.1055/a-1700-3520
       
  • Concise Syntheses of Alternariol, Alternariol-9-monomethyl Ether and Their
           D3-Isotopologues

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      Authors: Sebald; Michael A., Gebauer, Julian, Koch, Matthias
      Abstract: Alternariol (AOH) and alternariol-9-monomethyl ether (AME) are two secondary metabolites of Alternaria fungi which can be found in various foodstuffs like tomatoes, nuts, and grains. Due to their toxicity and potential mutagenic activity the need for the development of high-throughput methods for the supervision of AOH and AME levels is of increasing interest. As the availability of both native and labeled AOH and AME analytical standards is very limited, we herein present a novel and concise approach towards their synthesis by employing a ruthenium-catalyzed ortho-arylation as the key step. Finally, we demonstrate their suitability as internal standards in stable-isotope dilution assay (SIDA)-HPLC-MS/MS analysis, a technique commonly used for the quantification of natural products in food and feed.
      Citation: Synthesis ; : -
      PubDate: 2021-11-16T00:00:00+0100
      DOI: 10.1055/a-1698-8328
       
  • Regioselective Amination or Alkoxylation of Halogenated Amino-, Thio- or
           Alkoxypyridines via Pyridyne Intermediates

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      Authors: Heinz; Benjamin, Djukanovic, Dimitrije, Siemens, Fiona, Idriess, Mohamed, Martin, Benjamin, Knochel, Paul
      Abstract: The treatment of 3-halopyridines (Cl, Br) bearing an R-substituent in position 2 (R = OEt, NEt2, N-piperidyl, or SEt) or in position 5 (R = OMe, OEt, SEt, NMe2, NEt2, or aryl) with KHMDS and an amine at 25 °C for 12 hours in THF provided regioselectively 3- and 4-aminated pyridines in 56–90% yields. The reaction of 3-bromo-2-diethylaminopyridine with various alcohols in the presence of t-BuOK/18-crown-6 in THF at 80 °C for 20–60 hours gave various 4-alkoxy-2-diethylaminopyridines in 61–81% yields. These substitution reactions were proposed to proceed via pyridyne intermediates.
      Citation: Synthesis ; : -
      PubDate: 2021-11-11T00:00:00+0100
      DOI: 10.1055/s-0037-1610786
       
  • On the Synthesis of a Novel Chiral Phosphorodiamidic Acid Containing­ the
           α-Phenylethyl Moiety: Insights on its Conformation and Reactivity

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      Authors: Cruz-Hernández; Carlos, Juaristi, Eusebio
      Abstract: A few years ago, the synthesis of chiral phosphoric acids supported on chiral BINOL frameworks was accomplished by T. Akiyama and M. Terada. Subsequent relevant applications demonstrated the importance of chiral phosphoric acids as privileged chiral inducers in asymmetric organocatalysis. In the present report, we discuss the development of novel chiral phosphorodiamidic acids derived from C 2-symmetric trans-1,2-diaminocyclohexane aliphatic frameworks. The preparation of the new chiral Brønsted acids, based on the intermediacy of a 1,3,2-diheterophospholan-2-oxide moiety, turned out to be challenging since several plausible synthetic methodologies proved to be ineffective. Furthermore, the five-membered heterocyclic moiety turned out to be easily hydrolyzed when exposed to nucleophilic alcohols or water. Complementary to the successful multistep synthesis reported here, it was possible to obtain crystals of the key precursor of the desired phosphorodiamidic acid, which proved suitable for X-ray diffraction analysis and hence to establish important conformational characteristics of the novel heterocycle.
      Citation: Synthesis ; : -
      PubDate: 2021-11-08T00:00:00+0100
      DOI: 10.1055/a-1689-3626
       
  • Hydrogenation of Olefins, Alkynes, Allenes, and Arenes by Borane-Based
           Frustrated Lewis Pairs

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      Authors: Wech; Felix, Gellrich, Urs
      Abstract: In recent years, borane-based frustrated Lewis pairs have proved to be efficient hydrogenation catalysts and they have become an alternative to transition-metal-based systems. The hydrogen activation by classic FLPs leads to a protonated Lewis base and a borohydride. Consequently, hydrogenations catalyzed by classic FLPs consist of stepwise hydride transfer reactions and protonations (or vice versa). More recently, systems that operate via an initial hydroboration have allowed the substrate scope for FLP-catalyzed hydrogenations to be extended. In this review, hydrogenations of organic substrates catalyzed by borane­-based frustrated Lewis pairs are discussed. Emphasis is given to the mechanistic aspects of these catalytic reactions.1 Introduction2 FLP-Catalyzed Hydrogenation of Polarized Double Bonds2.1 Hydrogenation of Michael Acceptors by FLPs2.2 Asymmetric Hydrogenation of Polarized Double Bonds2.3 Hydrogenation of Arenes and N-Heterocycles3 Hydrogenation of Unactivated Olefins and Alkynes3.1 Hydrogenation of Olefins and Alkynes by an Initial Hydroboration4 Summary and Outlook
      Citation: Synthesis ; : -
      PubDate: 2021-11-02T00:00:00+0100
      DOI: 10.1055/a-1684-5552
       
  • Cationic Iridium/Chiral Bidentate Phosphoramidite Catalyzed Asymmetric
           Hydroarylation

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      Authors: Shirai; Tomohiko, Yamamoto, Yasunori
      Abstract: In this personal account, we summarize our investigations on the asymmetric direct addition of C(sp2)–H bonds to unsaturated bonds, such as C=O and C=C, using cationic iridium/chiral O-linked bidentate phosphoramidite (Me-BIPAM) and S-linked bidentate phosphoramidite (S-Me-BIPAM) catalyst systems.1 Introduction2 Highly Enantioselective Intramolecular Hydroarylation of α-Keto Amides3 Highly Enantioselective Intermolecular Hydroarylation of Bicyclo­alkenes4 Conclusion
      Citation: Synthesis ; : -
      PubDate: 2021-11-01T00:00:00+0100
      DOI: 10.1055/a-1683-9455
       
  • Recent Advances on Transition-Metal-Catalyzed Asymmetric C–H
           Arylation Reactions

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      Authors: Li; Mingliang, Wang, Jun
      Abstract: Transition-metal-catalyzed asymmetric C–H functionalization has become a powerful strategy to synthesize complex chiral molecules. Recently, catalytic enantioselective C–H arylation has attracted great interest from organic chemists to construct aryl-substituted chiral compounds. In this short review, we highlight recent advances in asymmetric C–H arylation from 2019 to late 2021, including enantioselective C(sp2)–H arylation to construct axial or planar chiral compounds, and enantioselective C(sp3)–H arylation to introduce central chirality via desymmetrization of the methyl group or methylene C–H activation. These processes proceed with palladium, rhodium, iridium, nickel, or copper catalysts, and utilize aryl halides, boron, or diazo derivatives as arylation reagents.1 Introduction2 Transition-Metal-Catalyzed Asymmetric C(sp2)–H Arylation2.1 Chelation-Assisted Asymmetric C(sp2)–H Arylation for the Construction of Atropisomer2.2 Chelation-Assisted Asymmetric C(sp2)–H Arylation for the Construction of Planar Chiral Compounds2.3 Chelation-Assisted Asymmetric C(sp2)–H Arylation and Axial-to-Central Chirality Transfer for the Construction of Spirocycles2.4 Other Asymmetric C(sp2)–H Arylation Reactions3 Transition-Metal-Catalyzed Asymmetric C(sp3)–H Arylation3.1 Chelation-Assisted Enantioselective C(sp3)–H Arylation through Desymmetrization3.2 Chelation-Assisted Enantioselective Methylene C(sp3)–H Aryl­ation3.3 Other Asymmetric C(sp3)–H Arylations4 Conclusion and Outlook
      Citation: Synthesis ; : -
      PubDate: 2021-10-25T00:00:00+01:00
      DOI: 10.1055/a-1677-5870
       
  • Enantioselective C–H Alkylation of N-Arylbenzamides with Vinyl Ethers
           Catalyzed by an Iridium/Chiral Phosphoramidite–Olefin Complex

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      Authors: Murakami; Kotone, Sakamoto, Kana, Nishimura, Takahiro
      Abstract: Chiral phosphoramidite–olefin hybrid ligands were found to be effective in the iridium-catalyzed asymmetric alkylation of N-arylbenzamides with vinyl ethers. The reaction is catalyzed by a hydroxo­iridium catalyst coordinated with the hybrid ligand to give the corresponding products in high yields with high branch selectivity and enantioselectivity.
      Citation: Synthesis ; : -
      PubDate: 2021-10-19T00:00:00+01:00
      DOI: 10.1055/a-1672-6284
       
  • Synthesis of Ruthenium Catalysts with a Chiral Arene Ligand Derived from
           Natural Camphor

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      Authors: Pototskiy; Roman A., Boym, Mikhail A., Nelyubina, Yulia V., Perekalin, Dmitry S.
      Abstract: A ruthenium complex with a chiral arene ligand [(camphor–arene)RuCl2]2 was synthesized by the reaction of RuCl3·nH2O with a chiral diene which was obtained from natural camphor in three steps. This complex catalyzed the asymmetric hydrogenation of acetophenone (64–85% ee), but decomposed in catalytic reactions involving C–H activation of 2-phenylpyridine or benzoic acid derivatives.
      Citation: Synthesis ; : -
      PubDate: 2021-10-13T00:00:00+01:00
      DOI: 10.1055/a-1668-2075
       
  • Asymmetric C–H Functionalization Enabled by Pd/Chiral Phosphoric
           Acid Combined Catalysis

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      Authors: Wang; Pu-Sheng, Gong, Liu-Zhu
      Abstract: Over the past decade, the combination of chiral phosphoric acid and palladium catalysis has emerged as a robust strategy to accomplish the regio- and stereoselective functionalization of inactive C–H bonds, enabling access to various types of chirality (central, planar, and axial). This review article describes the origin and advances in the asymmetric functionalization of allylic C–H, C(sp2)–H, and C(sp3)–H bonds enabled by chiral phosphoric acid and palladium combined catalysis.1 Introduction2.1 Enantioselective Allylic C–H Functionalization2.2 Enantioselective Non-allylic C(sp3)–H Functionalization2.3 Enantioselective C(sp2)–H Functionalization3 Conclusion
      Citation: Synthesis ; : -
      PubDate: 2021-10-06T00:00:00+01:00
      DOI: 10.1055/a-1662-7096
       
  • Modular Synthesis of Carbazole-Substituted Phthalimides as Potential
           Photocatalysts

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      Authors: Gonda; Zsombor, Földesi, Tamás, Nagy, Bálint, Novák, Zoltán
      Abstract: The modular synthesis of carbazole functionalized phthalimides (PIs) and their applicability as catalyst in selected photocatalytic transformations are reported. The developed synthetic approach provides high variability of phthalimide considering that the synthesis of the phthalimide core can be easily performed. Starting from fluorophthalic acid anhydrides, the corresponding fluorophthalimides were prepared with various amines, and the fluoro function ensured the introduction of carbazoles into the phthalimide framework through aromatic nucleophilic substitution. Besides the synthetic developments, some of the carbazolyl phthalimides were tested in four different photocatalytic transformations, which showed attractive and comparable activity to the known 4-CzIPN and noble metal complexes.
      Citation: Synthesis ; : -
      PubDate: 2021-09-17T00:00:00+01:00
      DOI: 10.1055/a-1647-7292
       
  • Direct Copper-Catalyzed C-3 Arylation of Diphenylphosphine Oxide Indoles

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      Authors: Huang; Xiao-Ling, Li, Chong, Wang, Juan, Yang, Shang-Dong
      Abstract: We have developed a simple and effective method for the C-3 arylation of phosphorus-containing indole compounds in the presence of CuI under mild conditions. This reaction provides a reliable method for the modification of ligands.
      Citation: Synthesis ; : -
      PubDate: 2021-09-03T00:00:00+01:00
      DOI: 10.1055/a-1633-8792
       
  • Synthesis of Nitrile-Functionalized Polydentate N-Heterocycles as Building
           Blocks for Covalent Triazine Frameworks

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      Authors: Everaert; Jonas, Debruyne, Maarten, Vanden Bussche, Flore, Van Hecke, Kristof, Heugebaert, Thomas S. A., Van Der Voort, Pascal, Van Speybroeck, Veronique, Stevens, Christian V.
      Abstract: Covalent triazine frameworks (CTFs) based on polydentate ligands are highly promising supports to anchor catalytic metal complexes. The modular nature of CTFs allows to tailor the composition, structure, and function to its specific application. Access to a broad range of chelating building blocks is therefore essential. In this respect, we extended the current available set of CTF building blocks with new nitrile-functionalized N-heterocyclic ligands. This paper presents the synthesis of the six ligands which vary in the extent of the aromatic system and the denticity. The new building blocks may help in a rational design of enhanced support materials in catalysis.
      Citation: Synthesis ; : -
      PubDate: 2021-08-31T00:00:00+01:00
      DOI: 10.1055/a-1626-5749
       
  • Ruthenium(II)/Chiral Carboxylic Acid Catalyzed Enantioselective C–H
           Functionalization of Sulfoximines

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      Authors: Huang; Long-Tao, Hirata, Yuki, Kato, Yoshimi, Lin, Luqing, Kojima, Masahiro, Yoshino, Tatsuhiko, Matsunaga, Shigeki
      Abstract: Ruthenium(II)-catalyzed enantioselective C–H functionalization reactions of sulfoximines with sulfoxonium ylides are described. The combination of [RuCl2(p-cymene)]2 and a pseudo-C 2-symmetric binaphthyl monocarboxylic acid furnished the S-chiral products in 76:24 to 92:8 er.
      Citation: Synthesis ; : -
      PubDate: 2021-08-16T00:00:00+01:00
      DOI: 10.1055/a-1588-0072
       
  • Sulfur-Based Chiral Iodoarenes: An Underexplored Class of Chiral
           Hypervalent Iodine Reagents

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      Authors: Elsherbini; Mohamed, Osi, Arnaud, Alharbi, Haifa, Karam, Fatemah, Wirth, Thomas
      Abstract: Chiral hypervalent iodine reagents are active players in modern stereoselective organic synthesis. Structurally diverse chiral hypervalent iodine reagents have been synthesised and extensively studied, but hypervalent iodine reagents containing chiral sulfur stereogenic centre are scarce and their synthesis is challenging. A small library of iodoarenes containing chiral sulfinamide and chiral sulfoximine moieties has been synthesised using commercially available reagents. The oxidation of the chiral iodoarene precursors to iodine(III) reagents was cumbersome due to facile overoxidation of the sulfoxide moiety and hence loss of chirality under various oxidation conditions. Oxidation of chiral sulfonimidoyl derivatives to the corresponding hypervalent iodine reagents was successful and led to novel sulfur-based chiral iodine(III) reagents.
      Citation: Synthesis ; : -
      PubDate: 2021-05-14T00:00:00+01:00
      DOI: 10.1055/a-1508-9593
       
  • Synthesis of Cyclic Phosphinates by Microwave-Assisted
           Ionic-Liquid-Promoted Alcoholysis

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      Authors: Harsági; Nikoletta, Kiss, Nóra Zsuzsa, Drahos, László, Keglevich, György
      Abstract: A series of 1-alkoxy-3-methyl- and 3,4-dimethyl-3-phospholene 1-oxides, as well as 1-alkoxy-3-methylphospholane 1-oxides were prepared in good yields by the microwave (MW)-assisted [bmim][PF6]-catalyzed transesterification of the corresponding methyl or ethyl esters. The alcoholyses studied represent another case, where MW irradiation has had a crucial role on the course of the reaction. The method developed is an alternative possibility to other esterifications starting from the corresponding phosphinic chlorides and acids.
      Citation: Synthesis ; : -
      PubDate: 2021-05-10T00:00:00+01:00
      DOI: 10.1055/a-1504-8924
       
  • Regio- and Stereoselective (SN2) N-, O-, C- and S-Alkylation Using
           Trialkyl Phosphates

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      Authors: Banerjee; Amit, Hattori, Tomohiro, Yamamoto, Hisashi
      Abstract: Bimolecular nucleophilic substitution (SN2) is one of the most well-known fundamental reactions in organic chemistry to generate new molecules from two molecules. In principle, a nucleophile attacks from the back side of an alkylating agent having a suitable leaving group, most commonly a halide. However, alkyl halides are expensive, very harmful, toxic and not so stable, which makes them problematic for laboratory use. In contrast, trialkyl phosphates are inexpensive, readily accessible and stable at room temperature, under air, and are easy to handle, but rarely used as alkylating agents in organic synthesis. Here, we describe a mild, straightforward and powerful method for nucleophilic alkylation of various N-, O-, C- and S-nucleophiles using readily available trialkyl phosphates. The reaction proceeds smoothly in excellent yield, and quantitative yield in many cases, and covers a wide range of substrates. Further, the rare stereoselective transfer of secondary alkyl groups has been achieved with inversion of configuration of chiral centers (up to 98% ee).
      Citation: Synthesis ; : -
      PubDate: 2021-05-10T00:00:00+01:00
      DOI: 10.1055/a-1504-8366
       
 
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