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Tetrahedron Letters
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ISSN (Print) 0040-4039 - ISSN (Online) 1359-8562
Published by Elsevier Homepage  [3185 journals]
  • Graphical abstract TOC cont’d
    • Abstract: Publication date: 3 October 2019Source: Tetrahedron Letters, Volume 60, Issue 40Author(s):
       
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    • Abstract: Publication date: 3 October 2019Source: Tetrahedron Letters, Volume 60, Issue 40Author(s):
       
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    • Abstract: Publication date: 3 October 2019Source: Tetrahedron Letters, Volume 60, Issue 40Author(s):
       
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    • Abstract: Publication date: 26 September 2019Source: Tetrahedron Letters, Volume 60, Issue 39Author(s):
       
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    • Abstract: Publication date: 26 September 2019Source: Tetrahedron Letters, Volume 60, Issue 39Author(s):
       
  • Contents continued
    • Abstract: Publication date: 26 September 2019Source: Tetrahedron Letters, Volume 60, Issue 39Author(s):
       
  • One-pot synthesis of 2-substituted thieno[3,2-b]indoles from
           3-aminothiophene-2-carboxylates through in situ generated
           3-aminothiophenes
    • Abstract: Publication date: Available online 19 September 2019Source: Tetrahedron LettersAuthor(s): Roman A. Irgashev, Alexander S. Steparuk, Gennady L. Rusinov A convenient protocol for one-pot synthesis of thieno[3,2-b]indoles, bearing aromatic, thien-2-yl or styryl fragments at C-2 position, from easily accessible 5-substituted 3-aminothiophene-2-carboxylates using the Fischer indolization reaction, was developed during this study. Two main steps of this approach are the saponification of the starting 3-aminoesters with sodium hydroxide and next treatment of the crude 3-aminoacids sodium salts with arylhydrazines in glacial acetic acid solution. The latter step includes in situ decarboxylation of the freed 3-aminothiophene-2-caboxylic acids to the 3-aminothiophenes and their acid promoted reaction with arylhydrazines to initially form arylhydrazones of 5-substituted thiophene-3(2H)-ones, which smoothly cause indolization to afford the desired thieno[3,2-b]indoles.Graphical abstractGraphical abstract for this article
       
  • One-pot synthesis of (E)-3-benzylideneflavanones from
           2-hydroxyacetophenones and aromatic aldehydes
    • Abstract: Publication date: Available online 18 September 2019Source: Tetrahedron LettersAuthor(s): Lishou Yang, Enhua Wang, Yanhua Fan, Juan Yang, Zhongsheng Luo, Yu Wang, Mei Peng, Tingfei Deng, Xiaosheng Yang An efficient and practical PPA/H2SO4 promoted synthesis of (E)-3-benzylideneflavanones from 2-hydroxyacetophenones and aromatic aldehydes was developed. Various (E)-3-benzylideneflavanones were produced in good to excellent yields.Graphical abstractGraphical abstract for this article
       
  • Isatins 3-C Annulation vs Ring-opening: Two different Pathways for
           Synthesis of Spiro Compounds via Multicomponent Reactions
    • Abstract: Publication date: Available online 18 September 2019Source: Tetrahedron LettersAuthor(s): Qingqing Niu, Junhua Xi, Lei Li, Li Li, Chengli Pan, Meijun Lan, Liangce Rong An efficient synthesis of spiro compounds via two different pathways from the reactions of isatins, 3-phenylisoxazol-5(4H)-one (3-ethylisoxazol-5(4H)-one), and pyrazol-5-amine (6-aminopyrimidine-2,4(1H,3H)-dione) were reported. The catalyst Amberlyst-15 could be easy recycled and reused for many time without any appreciable loss in catalytic activity. The new type spiro compounds were gained through the ring-opening of isatins process. The structures of spiro[indoline-3,4'-isoxazolo[5,4-b]pyrazolo[4,3-e]pyridin]-2-one, spiro[isoxazolo[5,4-b]quino line-4,5'-pyrrolo[2,3-d]pyrimidine]-2',4',6'(1'H,3'H,7'H)-trione, and spiro[indoline-3,4'-pyrazolo[3,4-b]pyridine]-2,6'(5'H)-dione were successfully confirmed by 1H NMR, 13C NMR, HRMS, and X-ray crystal diffraction analysis.Graphical abstractGraphical abstract for this article
       
  • Aldehyde-functionalized dithienylethenes with extended π-systems as
           versatile building blocks for NIR photochromic materials
    • Abstract: Publication date: Available online 18 September 2019Source: Tetrahedron LettersAuthor(s): Ziyong Li, Ming Qin, Xiaotong Du, Yuqing Wang, Wenjing Niu, Mo Wang, Libing Li, Zhenqi Zhang, Zhiqiang Lu A series of aldehyde-functionalized dithienylethenes 1b, 1c, 2b and 2c with extended π-conjugated systems have been synthesized by Wittig reaction. Their structures are confirmed by 1H NMR, 13C NMR and HRMS (ESI). As expected, investigation on their photochromic properties indicates that dithienylethenes 1b, 1c, 2b and 2c have good photochromic behaviors with excellent fatigue resistance upon irradiation with UV or visible light. The DFT calculations further validate the differences in their photochromic properties in solution. Furthermore, they can be utilized as versatile building blocks to construct novel near-infrared photochromic materials.Graphical abstractGraphical abstract for this article
       
  • Dicitrinones E and F, Citrinin Dimers from the Marine Derived Fungus
           Penicillium citrinum HDN-152-088
    • Abstract: Publication date: Available online 18 September 2019Source: Tetrahedron LettersAuthor(s): Lu Wang, Changlong Li, Guihong Yu, Zichao Sun, Guojian Zhang, Qianqun Gu, Tianjiao Zhu, Qian Che, Huashi Guan, Dehai Li Two new citrinin dimers named dicitrinones E and F (1 and 2), together with one biogenetically related known citrinin monomer (3), were isolated from the marine derived fungus Penicillium citrinum HDN-152-088. All structures including the absolute configurations were elucidated on the basis of comprehensive spectroscopic data, and assisted by ECD calculations. Among them, compounds 1 and 2 belong to the class of citrinin dimers with a rare carbon-bridged C-7/C-7′ linkage. Compound 1 displayed antioxidant activity with IC50 value of 23.73 μM.Graphical abstractGraphical abstract for this article
       
  • Iron/Copper Co-Catalyzed Highly Selective Arylation of Sulfinamides with
           Aryl Iodides
    • Abstract: Publication date: Available online 18 September 2019Source: Tetrahedron LettersAuthor(s): Shuanglin Qin, Yunhao Luo, Yue Sun, Le Tian, Shende Jiang, Jun yan, Guang Yang In the present study, an inexpensive but efficient Iron(III) and Copper(II) co-catalyst without ligands catalyzed arylation of sulfinamides with aryl iodide was primarily reported. In brief, in the presence of Fe(NO3)3•9H2O, CuO and K3PO4, the highly selective C−N cross coupling of several sulfinamides and aryl iodides was achieved in high chemical yield, while the aryl chlorides and bromides could not yield coupling products. It is noteworthy that through the arylation of chiral tert-butanesulfinamide with aryl iodides, N-aryl tert-butanesulfinamides are provided without racemization, even in gram-scale. The possible mechanism was that This oxidative addition process between copper catalyst and aryl-iodides might be significantly accelerated by active Fe(III) species. Moreover, using this synthetic method, a facile and efficient access was developed for the derivatives of N-phenyl sulfinamides, which might help to develop new drug molecules and material chemicals.Graphical abstractGraphical abstract for this article
       
  • Synthesis and Antibacterial Activity of Four Natural Chalcones and Their
           Derivatives
    • Abstract: Publication date: Available online 17 September 2019Source: Tetrahedron LettersAuthor(s): Yuanyuan Li, Bingxia Sun, Jiadai Zhai, Lin Fu, Shuxin Zhang, Jing Zhang, Hongliang Liu, Wenhai Xie, Hongkuan Deng, Zhiwei Chen, Feng Sang Four natural chalcones bearing hydroxyisoprenyl or prenyl groups, named Paratocarpin E (2), Xanthoangelol D (3), Angusticornin A (4) and Kanzonol C (5), were prepared by employing the Claisen-Schmidt condensation as the key step. In an attempt to investigate the effect of the hydroxyisoprenyl group on biological activity, two of their derivatives were also prepared for antibacterial activity research. The synthesized compounds were investigated for their expected antibacterial activities against Gram positive bacteria (Bacillus subtilis, Staphylococcus aureus) as well as Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa). Paratocarpin E (2) was found to be the most potent against two Gram positive bacteria while the majority of the remaining compounds showed promising activity as well. However, all of the compounds were inactive against both Gram-negative bacteria.Graphical abstractGraphical abstract for this article
       
  • Studies towards the stereoselective total synthesis of Gliomasolide A
    • Abstract: Publication date: Available online 17 September 2019Source: Tetrahedron LettersAuthor(s): Kare Nagaraju, Govinda Reddy Kundoor, Palakodety Radha Krishna The first synthetic approach towards the Gliomasolide A is described in 15 linear steps with 4% overall yield. The key steps in this approach are RCM protocol for the construction of 14-member macrolide, a Sharpless kinetic resolution, Keck and Brown’s allylations for the installation of desired stereocenters.Graphical abstractGraphical abstract for this article
       
  • Synthesis of Diverse Libraries of Carboxamides via Chemoselective
           N-Acylation of Amines by Carboxylic acids Employing Brønsted Acidic IL
           [BMIM(SO3H)][OTf]
    • Abstract: Publication date: Available online 17 September 2019Source: Tetrahedron LettersAuthor(s): Hemantkumar M. Savanur, Shruti S. Malunavar, Pavankumar Prabhala, Suraj M Sutar, Rajesh G. Kalkhambkar, Kenneth K. Laali Chemoselective N-acylation of amines with carboxylic acids as acyl electrophiles and Brønsted acidic IL [BMIM(SO3H)][OTf] as promoter is reported under both thermal and microwave irradiation to produce libraries of carboxamides in good to excellent yields after a simple workup. The protocol is compatible with structurally diverse 1o and 2o amines and works in the presence of sensitive functional groups such as thiols and phenols. The potential for recycling and reuse of the IL is also demonstrated.Graphical abstractGraphical abstract for this article
       
  • Nickel-catalyzed [2+2] cycloaddition reaction using bisallenes
    • Abstract: Publication date: Available online 17 September 2019Source: Tetrahedron LettersAuthor(s): Shigeru Arai, Yuna Kawata, Yuka Amako, Atsushi Nishida A nickel-catalyzed [2+2] cycloaddition of bisallenes has been described. Simple bisallenes are employed for the formation of “head to head” cycloadducts in the presence of Ni(0) with xantphos. The dienyl moiety in a product were applicable for various [4+2] cycloaddition reactions. Allene-allenamides under Ni-xantphos system gave the tricyclic compounds through sequential [2+2]–[4+2] cycloaddition reaction in highly stereoselective manner.Graphical abstractGraphical abstract for this article
       
  • CuI-catalyzed highly regioselective C-H functionalization of indoles using
           indole-3-tosylhydrazons as carbene precursor: An efficient synthesis of
           3,3-bis(indolyl)methane derivatives
    • Abstract: Publication date: Available online 17 September 2019Source: Tetrahedron LettersAuthor(s): Priya kamboj, Sunil Dutt, Sourav Chakroborty, Vikas Tyagi Herein, we have developed a novel approach for synthesizing symmetrical and unsymmetrical 3,3-bis(indolyl)methane derivatives via CuI-catalyzed C-H functionalization of indole using indole-3-tosylhydrazones as carbene precursor. This procedure works well with different substitutions such as NO2, Br, CH3 and OMe on indole or indole-3-tosylhydrazones and features high regioselectivity for C-3 functionalization over the C-1 and N-1 positions. Further, we have also revealed the feasibility of this protocol in a one-pot fashion starting from indole-3-carboxyaldehyde.Graphical abstractGraphical abstract for this article
       
  • A New Route to 1,2,3-Triazole Fused Benzooxazepine and Benzodiazepine
           Analogues Through Metal-free Intramolecular Azide-Olefin Oxidative
           Cycloaddition
    • Abstract: Publication date: Available online 17 September 2019Source: Tetrahedron LettersAuthor(s): D. Gangaprasad, J. Paul Raj, K. Karthikeyan, R. Rengasamy, M. Kesavan, M. Vajjiravel, J. Elangovan A collection of 1,2,3-Triazole fused benzooxazepine and benzodiazepine analogues was prepared by one pot azide substitution and intramolecular azide-olefin oxidative cycloaddition sequence under metal-free conditions.Graphical abstractGraphical abstract for this article
       
  • Talarophenol sulfate and talarophilones from the Australian mud dauber
           wasp-associated fungus, Talaromyces sp. CMB-W045
    • Abstract: Publication date: Available online 16 September 2019Source: Tetrahedron LettersAuthor(s): Pabasara Kalansuriya, Zeinab G. Khalil, Angela A. Salim, Robert J. Capon Chemical analysis of a jasmine rice cultivation of an Australian mud dauber wasp-associated fungus, Talaromyces sp. CMB-W045, led to the discovery of a new p-terphenyl, talarophenol sulfate (1). The structure elucidation of 1 was achieved by detailed spectroscopic analysis supported by acid hydrolysis to the p-hydroquinone talarophenol (2), and subsequent in situ air oxidation to trace amounts of the p-quinone talaroquinone (3). The same jasmine rice cultivation also yielded the new talarophilones A (4) and B (5), and known (+)-mitorubrin (6) and pochonin D (7), with structures assigned by detailed spectroscopic analysis. Neither 1 or 4-7 exhibited growth inhibitory properties against a panel of human cell lines, or bacterial or fungal pathogens, although 1 did exhibit selective antibacterial activity against Streptococcus pyogenes ATCC 12344 (IC50 10 µM).Graphical abstractGraphical abstract for this article
       
  • Stereoselective C-X and Regioselective C-H activation to, and selective
           C(sp2 )-C(sp3 ) reductive elimination from, platinum compounds with
           thiophene-derived ligands
    • Abstract: Publication date: Available online 16 September 2019Source: Tetrahedron LettersAuthor(s): Craig M. Anderson, Garrett Brown, Matthew W. Greenberg, David Yu, Nellie Bowen, Rahma Ahmed, Melissa Yost-Bido, Alina Wray Several thiophene-based N^C ligands were synthesized. Strategically, a bromide was incorporated on the 2-position of the thiophene ring. When allowed to react with the platinum tetramethyl dimer, [Pt2Me4(µ-SMe2)2], platinum(IV) platinacycles were formed by oxidative addition of the C(sp2)-X bond. These platinum(IV) compounds were characterized by NMR and HRMS. The platinum (IV) compounds were subsequently subjected to thermolysis. A series of reactions occurred, including selective C-C reduction elimination and selective C-H oxidative addition, giving mixtures of platinum(II) products with varying degrees of regioselectivity.Graphical abstractGraphical abstract for this article
       
  • In(OTf)3 catalyzed reductive etherification of 2-aryloxybenzaldehydes and
           2-(arylthio)benzaldehydes
    • Abstract: Publication date: Available online 17 July 2019Source: Tetrahedron LettersAuthor(s): Anamika Prajapati, Mahendra Kumar, Ranjit Thakuria, Ashok K. Basak 2-Aryloxybenzaldehydes and 2-(arylthio)benzaldehydes undergo reductive etherification in presence of 5 mol% In(OTf)3 and stoichiometric amount of Et3SiH under solvent free conditions to generate novel symmetrical dibenzyl ethers and thioethers in excellent yields. In(OTf)3 is found to be superior in terms of catalytic activity over the other metal triflates tested for the reaction. Xanthenes and thioxanthenes, as anticipated, could not be obtained under these conditions.Graphical abstractGraphical abstract for this article
       
  • A novel synthesis of 3-hydroxypiperidin-2-ones via site-selective
           difunctionalization of piperidine derivatives
    • Abstract: Publication date: Available online 16 September 2019Source: Tetrahedron LettersAuthor(s): Fang Wang, Xinying Zhang, Yan He, Xuesen Fan An efficient and novel synthesis of 3-hydroxypiperidin-2-ones via site-selective difunctionalization of the inert C(sp3)−H bonds of N-substituted piperidine derivatives is presented. Mechanistically, the formation of the title compounds is believed to go through a cascade process featuring with the sequential formation of cyclic enamine, oxiranium and iminium as key intermediates.Graphical abstractGraphical abstract for this article
       
  • Cephasinenoside A, a new cephalotane diterpenoid glucoside from
           Cephalotaxus sinensis
    • Abstract: Publication date: Available online 14 September 2019Source: Tetrahedron LettersAuthor(s): Chun-Xue Zhao, Bing-Qian Li, Zhao-Xiang Shao, Da-Hong Li, Yong-Kui Jing, Zhan-Lin Li, Hui-Ming Hua A new cephalotane diterpenoid glucoside, cephasinenoside A (1), was isolated from the twigs and leaves of Cephalotaxus sinensis (Rehd. et Wils.) Li. The structure of 1 was established on the basis of spectroscopic analyses and ECD calculations. Compound 1 represents the first cephalotane diterpenoid glycoside which inhibits the proliferation of human acute myeloid leukemia HL-60 cells with a GI50 value of 7.17 ± 1.03 μM.Graphical abstractCephasinenoside A is the first cephalotane diterpenoid glucoside isolated from Cephalotaxus sinensis. It was active against HL-60 cells with GI50 value of 7.17 ± 1.03 μM. The structure including absolute configuration was elucidated based on spectroscopic analyses and calculated ECD methods.Graphical abstract for this article
       
  • Access to 1,2,3-Triazole-Fused Isoindolines via an Unexpected Lewis Acid
           Catalyzed Cyclization Reaction
    • Abstract: Publication date: Available online 14 September 2019Source: Tetrahedron LettersAuthor(s): Xin Wang, Mengpei Bai, Meiqi Pei, Xinrui Xu, Die Wu, Siyang Xing, Kui Wang, Bolin Zhu, Hanyu Xia An unexpected cyclization reaction of N-sulfonyl 1,2,3-triazoles carrying the electron-deficient alkenes with amines under the catalysis of Lewis acid has been accomplished. This strategy involves the removal of the sulfonyl group and further intramolecular 1,4-addition, providing a series of 1,2,3-triazole-fused isoindoline compounds in good yields under the mild conditions.Graphical abstractGraphical abstract for this article
       
  • Photo-induced coupling of tertiary amines with Ugi-derived dehydroalanines
           as a practical device in the synthesis to 2,4-diaminobutyric acid
           derivatives
    • Abstract: Publication date: Available online 13 September 2019Source: Tetrahedron LettersAuthor(s): Katy Medrano-Uribe, Luis D. Miranda An Ir-mediated photocatalytic coupling of tertiary amines with Ugi-dehydroalanines was developed as an entry to medicinally important 2,4-diaminobutyric acid derivatives. In the process the 2,4-diaminobutyric acid framework is assembled directly embedded into a peptoide structure, via the construction of the C3(sp3)–C4(sp3) bond, through a C−H functionalization. The photocatalyzed oxidation of the tertiary amine produce a free radical intermediate which reacts with the double bond present in the dehydroalanines. The complete protocol comprises an Ugi 4-CR followed by an elimination reaction and the photo-induced coupling. Using this strategy, 15 new diversely substituted unnatural α,γ-diamino acids peptide derivatives were prepared in low to good yields.Graphical abstractGraphical abstract for this article
       
  • N-Heterocyclic carbene as a Brønsted base catalyst for the amination of
           naphthol derivatives and alcoholysis of glutaric anhydrides
    • Abstract: Publication date: Available online 13 September 2019Source: Tetrahedron LettersAuthor(s): K.R. Jayakrishnan, M. Tamilarasu, V. Jincy, Alagiri Kaliyamoorthy A non-covalent Brønsted-basic N-heterocyclic carbene catalyzed (NHC) Friedel-Crafts type amination of naphthol derivatives using dialkyl azodicarboxylates as the aminating source and alcoholysis of various glutaric anhydrides using alcohol as pronucleophile is presented. Both of these reactions are performed in the presence of either commercially available free-carbene catalyst or in situ-generated carbene catalyst. Friedel-Crafts type amination reaction is an example of a hydroxy group facilitated amination reaction. Both reactions proceed via in situ activations of –OH group by the carbene catalyst through hydrogen bonding interaction and furnish the relevant products in moderate to excellent yields.Graphical abstractGraphical abstract for this article
       
  • Recent progress on catalytic Heck carbonylations using carbon monoxide
           surrogates
    • Abstract: Publication date: Available online 13 September 2019Source: Tetrahedron LettersAuthor(s): Hideyuki Konishi, Kei Manabe Ongoing efforts toward the development of carbon monoxide (CO) surrogates have changed the way in which carbonylative transformations are conducted. For synthesizing carboxylic acid derivatives, Heck carbonylation using CO surrogates in slight excess has become a more efficient and practical method than the conventional one using large excess of CO gas. To supply CO for the reaction, both in-situ and ex-situ methods has been considered. Herein, we summarize recent progress in catalytic Heck carbonylation using CO surrogates, including discussion of the mechanism for CO generation from recently developed CO surrogates.Graphical abstractGraphical abstract for this article
       
  • One-pot reactions of bicyclic zinc enolate generated from Ni-catalyzed
           reductive cyclization to furnish octahydro-4,7-ethanobenzofuran-9-one
           derivatives
    • Abstract: Publication date: Available online 13 September 2019Source: Tetrahedron LettersAuthor(s): Tetsuya Tsujihara, Moriho Tomeba, Shigeaki Ohkubo-Sato, Kyoko Iwabuchi, Rino Koie, Natsumi Tada, Satoru Tamura, Tsunayoshi Takehara, Takeyuki Suzuki, Tomikazu Kawano The one-pot reactions of catalytically generated bicyclic zinc enolate with various electrophiles are reported. The zinc enolate as a key intermediate is efficiently delivered from Ni-catalyzed reductive cyclization of alkynyl cyclohexadienone. Employing aldehydes, imine, nitroalkene, andα,β -unsaturated carbonyl compounds as electrophiles, this new class of one-pot reactions gave multi-functionalized cis-hydrobenzofurans and octahydro-4,7-ethanobenzofuran-9-one derivatives in moderate to good yields.Graphical abstractGraphical abstract for this article
       
  • Synthetic directions towards Capsular Polysaccharide of Streptococcus
           pneumoniae Serotype 18C
    • Abstract: Publication date: Available online 13 September 2019Source: Tetrahedron LettersAuthor(s): Geeta Karki, Pintu Kumar Mandal An efficient synthetic strategy has been developed for the synthesis of the tri, tetrasaccharide block and pentasaccharide corresponding to the capsular polysaccharide of Streptococcus pneumonia serotype 18C as their 2-aminoethyl glycosides. A one-pot glycosylation-deprotection, sequential glycosylations strategy has been adopted for the construction of the fragments and pentasaccharide derivative, which were then transformed into target compound after a series of functional group transformations. The synthetic method relies on the use of p-methoxybenzyl ether as an in situ-removable protecting group to reduce the number of reaction steps significantly. Here H2SO4-silica has been used successfully as a promoter for all glycosylation reaction. In addition, the synthetic target also contained a free amino group at its reducing end, facilitating its conjugation with other molecules for various biological studies and applications.Graphical abstractGraphical abstract for this article
       
  • Regioselective Synthesis of C-Prenylated Flavonoids via Intramolecular
           [1,3] or [1,5] Shift Reaction Catalyzed by Acidic Clays
    • Abstract: Publication date: Available online 11 September 2019Source: Tetrahedron LettersAuthor(s): Wei Li, Liang Shu, Kexiong Liu, Qiuan Wang Prenyl side chain and dihydropyrano skeleton exists in many natural and synthetic biologically active flavonoids. A highly efficient and regioselective method for the synthesis of C-prenylated flavonoids via intramolecular [1,3] or [1,5] shift reaction of 5-O-prenylflavonoids catalyzed by Florisil or Montmorillonite clays is described. Florisil catalyzes intramolecular [1,5] shift reaction of 5-O-prenylflavonoids to obtain 8-C-prenylated flavonoids exclusively, Montmorillonite K10 exhibits the superior selectivity to promote intramolecular [1,3] shift reaction to obtain 6-C-prenylated flavonoids compared with Florisil and Montmorillonite KSF. This method provides a practical process to regioselective synthesize biologically important C-prenylated flavonoids in good yields using commercially available and inexpensive catalyst under mild conditions.Graphical abstractGraphical abstract for this article
       
  • Corrigendum to “AlCl3-promoted reaction of cycloalkanones with
           hydrazones: A convenient direct synthesis of
           4,5,6,7-tetrahydro-1H-indazoles and their analogues” [Tetrahedron Lett.
           60 (2019) 150988]
    • Abstract: Publication date: Available online 11 September 2019Source: Tetrahedron LettersAuthor(s): Rima Laroum, Fabienne Berrée, Thierry Roisnel, Vincent Dorcet, Bertrand Carboni, Abdelmadjid Debache
       
  • A silica-gel accelerated [4+2] cycloaddition-based biomimetic approach
           towards the first total synthesis of magterpenoid C
    • Abstract: Publication date: Available online 10 September 2019Source: Tetrahedron LettersAuthor(s): Dileep Kumar, Virendra Kumar, Abdus Salam, Tabrez Khan The first total synthesis of magterpenoid C has been realized via a silica gel accelerated biomimetic Diels-Alder reaction between β-myrcene and randaiol derived quinone. However, application of similar strategy towards magterpenoid B via a protective Diels-Alder reaction failed to deliver the natural product.Graphical abstractGraphical abstract for this article
       
  • Tandem Reaction of Heterocyclic Ketene Aminals with Diazoesters: Synthesis
           of Pyrimidopyrrolidone Derivatives
    • Abstract: Publication date: Available online 10 September 2019Source: Tetrahedron LettersAuthor(s): Kaixiu Luo, Weina Li, Jun Lin, Yi Jin A tandem reaction of heterocyclic ketene aminals (HKAs) with diazoesters in the presence of a Cu catalyst is demonstrated for the efficient synthesis of pyrimidopyrrolidone derivatives. The reaction shows a broad substrate scope and excellent functional group tolerance. Our method provides rapid access to diverse pyrimidopyrrolidones in moderate to excellent yields under mild reaction conditions.Graphical abstractGraphical abstract for this article
       
  • Thalicfoetine, a novel isoquinoline alkaloid with antibacterial activity
           from Thalictrum foetidum
    • Abstract: Publication date: Available online 10 September 2019Source: Tetrahedron LettersAuthor(s): Cai-Feng Ding, Xu-Jie Qin, Hao-Fei Yu, Ya-Ping Liu, Xin-Hua Wang, Xiao-Dong Luo Thalicfoetine (1), the first O-bridged spiro-benzylisoquinoline alkaloid possesses a spiro tetrahydropyridine-furanone core, was isolated from the roots of Thalictrum foetidum. Its structure was elucidated by extensive spectroscopic analyses and ECD calculation. Moreover, 1 exhibited antibacterial activity against Bacillus subtilis significantly with MIC value of 3.12 μg/mL.Graphical abstractGraphical abstract for this article
       
  • Photoredox mediated C–N cross coupling of sulfoximines with aryl
           iodides
    • Abstract: Publication date: Available online 10 September 2019Source: Tetrahedron LettersAuthor(s): Sudhir Hande, Adelphe Mfuh, Scott Throner, Ye Wu, Qing Ye, XiaoLan Zheng A new photoredox-catalyzed C-N coupling reaction of sulfoximines with aryl halides has been developed for a general N-arylation of sulfoximines. The reactions proceed in the presence of visible light with high levels of chemoselectivity and a wide range of functionality is tolerated. There is a rapidly increasing interest in sulfoximines as pharmacophores in drug discovery and this new method offers potential in terms of high functional group tolerance and late-stage functionalization of compounds.Graphical abstractGraphical abstract for this article
       
  • Stereoselective Synthesis of C3-C17 and C18-C34 Subunits of Bullatanocin
           Utilizing α-Chloro Sulfide Intermediates
    • Abstract: Publication date: Available online 10 September 2019Source: Tetrahedron LettersAuthor(s): L. Raju Chowhan, Sadagopan Raghavan A convergent synthesis of bullatanocin is envisaged by the union of C18-C34, C3-C17 and the butenolide subunits. The synthesis of the C3-C17 and C18-C34 subunits is disclosed that takes advantage of the chirality of tartaric acid for 1,2-asymmetric induction, chloro sulfides for carbon chain elongation and [2], [3] sigmatropic shift for the preparation of 1,4-diol moiety via efficient 1,3-chirality transfer. The THF ring is elaborated by intramolecular displacement.Graphical abstractGraphical abstract for this article
       
  • Chiron Approach to Fully Functionalized Cyclohexane Frame of
           (+)-Resiniferatoxin
    • Abstract: Publication date: Available online 10 September 2019Source: Tetrahedron LettersAuthor(s): Y.N. Sambasiva Rao, Prathama S. Mainkar, Srivari Chandrasekhar The commercially available (-)-Shikimic acid is used to construct the fully functionalised cyclohexane frame (C-ring) of (+)-Resiniferatoxin. The key reactions involve stereo-selective epoxide opening with trimethylaluminium and vinyl Grignard reaction.Graphical abstractGraphical abstract for this article
       
  • Synthesis of a new chiral organocatalyst derived from (S)-proline
           containing a 1,2,4-triazolyl moiety and its application in the asymmetric
           aldol reaction. Importance of one molecule of water generated in situ
    • Abstract: Publication date: Available online 9 September 2019Source: Tetrahedron LettersAuthor(s): Omar Sánchez-Antonio, Eusebio Juaristi A simple and efficient preparation of a novel chiral derivative of (S)-proline containing a 1,2,4-triazolyl moiety is described. The high-yielding synthetic protocol includes the use of microwave irradiation to afford new chiral pyrrolidine derivatives in high yield. Our triazolyl-containing heterocycles was evaluated as organocatalyst (10 mol% load, under neat reaction conditions) in the enantioselective aldol reaction between four different types of ketones and a variety of aryl aldehydes. Good results in terms of enantioselectivity and chemical yield were observed under solvent-free reaction conditions and in the absence of any additive. Evidence is provided for the involvement of the water molecule generated upon enamine formation in the transition state of the aldol reaction.Graphical abstractGraphical abstract for this article
       
  • Alkaloids of NIRAM, Natural Dye from Polygonum tinctorium, and Their
           Anti-Inflammatory Activities
    • Abstract: Publication date: Available online 9 September 2019Source: Tetrahedron LettersAuthor(s): Dong Hyun Kim, Chung Sub Kim, Lalita Subedi, Sun Yeou Kim, Kang Ro Lee Phytochemical investigation of EtOH extract of NIRAM, natural dye from Polygonum tinctorium, resulted in the purification of nine alkaloid compounds (1-9) including four new compounds (1-4). Structures of these new compounds were elucidated by 1D and 2D NMR (1H and 13C NMR, 1H-1H COSY, 1H-13C HSQC, 1H-13C HMBC), IR, UV, HR-ESI-MS, and ECD spectra. Isolated compounds (1-9) were tested for their inhibitory effects on nitric oxide (NO) production in lipopolysaccharide (LPS)-activated BV-2 cells. Compounds 1-3, 5, and 7 showed potent NO production inhibitory activities, with IC50 values of 3.88-22.87 μM.Graphical abstractGraphical abstract for this article
       
  • 1,4-Dihydropyridine/BF3OEt2 for the reduction of imines: Influences of the
           amount of added BF3OEt2 and the substitution at N-1 and C-4 of the
           dihydropyridine ring
    • Abstract: Publication date: Available online 9 September 2019Source: Tetrahedron LettersAuthor(s): Ingrid F. Zattoni, Lais D. Guanaes, Letícia B. Cerqueira, Roberto Pontarolo, Diogo R.B. Ducatti, M. Eugênia R. Duarte, Miguel D. Noseda, Angela C.L.B. Trindade, Alan G. Gonçalves We have evaluated four 1,4-dihydropyridines (DHPs 1a, 1b, 1c and 1d) as reducing agents, which presented free (hydrogenated) or phenyl-substituted N-1 and C-4 positions of the DHP ring. Reactions combining each of the DHP and different amounts of BF3OEt2 were evaluated for the reduction of imine 2a (N-benzylideneaniline). DHP simultaneously substituted at N-1 and C-4 (1a), and DHP substituted at C-4 (1b) gave lower yields for reduction of 2a in comparison with DHPs 1c and 1d (both unsubstituted at the C-4 position). By evaluating the amount of added BF3OEt2 to the reaction mixture, we have found that DHP 1c (substituted at N-1) provided its best yield for amine 3a (82%) when associated with stoichiometric amounts BF3OEt2, while DHP 1d (N-1- and C-4-unsubstituted derivative) was more effective (90% yield) with catalytic quantities of the Lewis acid. The reaction system using DHP 1c under stoichiometric BF3OEt2 could also be successfully applied with additional imine examples and under reductive amination conditions.Graphical abstractGraphical abstract for this article
       
  • Acid-sensitive auxiliary assisted atypical diubiquitin synthesis
           exploiting thiol-ene coupling
    • Abstract: Publication date: Available online 9 September 2019Source: Tetrahedron LettersAuthor(s): Xiao Hua, Jing-Si Bai, Yi-Fu Kong, Guo-Chao Chu, Jing Shi, Yi-Ming Li Atypical ubiquitin (Ub) chains are generally involved in intracellular physiological processes, while the molecular mechanisms underlying their regulation remain unclear. In this work, we report an acid-sensitive auxiliary group based bifunctional handle that can prepare Lys27-, Lys29- and Lys33-diUb analogs by thiol-ene coupling (TEC) in combination with native chemical ligation (NCL). A prominent advantage of this method is the rapid and effective removal of acid-sensitive auxiliary groups after the formation of the isopeptide bond mimic. Collectively, this work illustrates the utility of the new strategy in the simple and efficient production of homogeneous atypical diUb analogs for biochemical and biophysical studies.Graphical abstractGraphical abstract for this article
       
  • A stereoselective synthesis of
           (R)-5-hydroxy-3-(4-methoxyphenethyl)cyclohex-2-enone, towards total
           synthesis of Prelunularin
    • Abstract: Publication date: Available online 9 September 2019Source: Tetrahedron LettersAuthor(s): Lakshmi Srinivasa Rao Kundeti, Sharada Ambati, N.M.A Rasheed, Ushakiranmayi Managamuri, Jhillu Singh Yadav, Kommu Nagaiah A first chiral strategy for synthesis of (R)-5-hydroxy-3-(4-methoxyphenethyl) cyclohex-2-enone reported. Key transformation includes Barbier allylation, ionic hydrogenation, Jefferey reaction, Katsuki Sharpless asymmetric epoxidation, reductive opening of epoxide and ring closing metathesis.Graphical abstractGraphical abstract for this article
       
  • An Organic-Inorganic Hybrid Comprised of Tetraphenylethene Peripheries and
           Octavinylsilsesquioxane Core for Aggregation-Induced Emission and
           Photoelectric Property
    • Abstract: Publication date: Available online 7 September 2019Source: Tetrahedron LettersAuthor(s): Zheng-Feng Chang, Bairong He, Hu Wang, Yuhao Zong, Xin Zhang, li Huang, Shule Zhang, Qin Zhong We designed and synthesized an organic-inorganic hybrid compound (TPE8-OV), which is comprised of an octavinylsilsesquioxane-core and TPE-peripheries. This compound exhibits good thermal stability and typical Aggregation-Induced Emission (AIE) characteristics. Interestingly, it shows good sensitivity to picric acid (PA), and the largest quenching constants of TPE8-OV is up to 174140 M-1. Furthermore, efficient non-doped OLEDs based on it afford remarkable performance.Graphical abstractGraphical abstract for this article
       
  • An efficient aerobic oxidative phosphonation of a-amino C–H bonds over
           CoNiFe hydrotalcite
    • Abstract: Publication date: Available online 7 September 2019Source: Tetrahedron LettersAuthor(s): Zhenzhen Xia, Lizhen Qin, Weiyou Zhou, Hui Wang, Binxun Yu, Zhonghua Sun, Junfeng Qian, Mingyang He An efficient and convenient heterogeneous catalytic procedure has been developed for the phosphonation of a-amino C–H bonds with various dialkyl phosphites and diarylphosphine oxides using molecular oxygen as a sustainable oxidant over CoNiFe hydrotalcite. The catalytic system could tolerate various tetrahydroquinoline derivatives, and the corresponding a-amino phosphonic compounds could be obtained in good to excellent yields. Synergistic effect might exist in the oxidative phosphonation under the catalysis of CoNiFe hydrotalcite.Graphical abstractGraphical abstract for this article
       
  • One-pot diastereoselective synthesis of tetrahydroepimino-benzo[b]azocines
           through sequential [3 + 2]-cycloaddition and Staudinger-aza-Wittig
           reactions
    • Abstract: Publication date: Available online 7 September 2019Source: Tetrahedron LettersAuthor(s): Xiaoming Ma, Xiaofeng Zhang, Guoshu Xie, John Mark Awad, Wei Zhang The one-pot synthesis of tetrahydro-epiminobenzo[b]azocines through a sequential 1,3-dipolar cycloaddition and intramolecular Staudinger-aza-Wittig reaction sequence is reported. This methodology provides a new and efficient approach for medium-sized and bridged nitrogen heterocyclic molecules.Graphical abstractGraphical abstract for this article
       
  • From acylethynylpyrroles to pyrrole-pyrone ensembles in a one step
    • Abstract: Publication date: Available online 6 September 2019Source: Tetrahedron LettersAuthor(s): Maxim D. Gotsko, Ivan V. Saliy, Lyubov' N. Sobenina, Igor A. Ushakov, Boris A. Trofimov Functionalized pyrrole-pyrone ensembles have been synthesized in up to 87% yields by KOH/MeCN [4+2]-cyclization of available acylethynylpyrroles with methylene active esters. The synthesized compounds, due to their potential rich chemistry, are rewarding building blocks for novel pyrrole-integrated complex molecules and promising precursors of medicine targeted compounds.Graphical abstractGraphical abstract for this article
       
  • Visible-light-promoted organic dye catalyzed perfluoroalkylation of
           hydrazones under mild conditions
    • Abstract: Publication date: Available online 6 September 2019Source: Tetrahedron LettersAuthor(s): Ming-Dong Zhou, Zhen Peng, Lei Li, He Wang A general and facile visible-light-promoted organic dye catalyzed perfluoroalkylation of hydrazones has been developed using inexpensive and non-toxic Eosin Y as the photoredox catalyst under mild conditions. This reaction protocol exhibits synthetic simplicity, broad scope of substrates, and excellent functional group compatibility. A gram scale synthesis can be also facilitated with a satisfactory yield, which opens up the possibility of practical applications.Graphical abstractGraphical abstract for this article
       
  • Regioselective single-step synthesis of 2-aminoimidazole derivatives
    • Abstract: Publication date: Available online 6 September 2019Source: Tetrahedron LettersAuthor(s): Erfei Li, Yifan Lin, Xin Wu, Xi Mao, Honglan Kang, Yihang Wen, Yihui Bai, Xiaoxia Wang, Xin Lv A convenient single-step strategy for the regioselective assembly of 2-aminoimidazole derivatives is herein described. Through a transition metal-free domino addition/cyclization process, the reactions of unsymmetrical carbodiimides with propargylic amines mediated by Cs2CO3 selectively afforded the corresponding polysubstituted 2-aminoimidazoles in moderate to good yields under very mild conditions. The regioselectivity was reversed in the presence of TEA at a higher temperature. The obtained 2-(o-iodoaryl)amino imidazoles could be easily converted to 2-(2-biphenyl)amino imidazole, 2-(o-alkynylphenyl)amino imidazole, benzoimidazo[1,2-a]imidazole and N-(imidazol-2-yl)indole derivatives.Graphical abstractGraphical abstract for this article
       
  • Diastereoselective synthesis of
           3-tert-butyl-3,4-dihydropyrazolo[5,1-c][1,2,4]triazine-3,4-diyl
           dicarboxylates
    • Abstract: Publication date: Available online 6 September 2019Source: Tetrahedron LettersAuthor(s): Sergey M. Ivanov, Andrey S. Dmitrenok, Konstantin A. Lyssenko The reactions of 3-tert-butyl-7-R1-8-R2-pyrazolo[5,1-c][1,2,4]triazines (R1 = H, Br; R2 = Me, n-Bu) with N-bromosuccinimide in the presence of R3CO2H (R3 = Me, t-Bu, Ph) afforded novel diastereomerically pure 3-tert-butyl-7-R1-8-R2-3,4-dihydropyrazolo[5,1-c][1,2,4]triazine-3,4-diyl dicarboxylates. The structures of the isolated products were established on the basis of IR, 1H, 13C, 2D NOESY NMR, high resolution mass spectrometry and X-ray single-crystal analysis. The steric and mechanistic origins of the observed regio- and stereoselectivity were also discussed.Graphical abstractGraphical abstract for this article
       
  • A novel approach to biologically relevant
           oxazolo[5,4-d]pyrimidine-5,7-diones via readily available diazobarbituric
           acid derivatives
    • Abstract: Publication date: Available online 6 September 2019Source: Tetrahedron LettersAuthor(s): Martha Gecht, Grigory Kantin, Dmitry Dar'in, Mikhail Krasavin An alternative route from 1,3-disubstituted barbituric acids to biologically relevant oxazolo[5,4-d]pyrimidine-5,7-diones was developed that features sulfonyl-azide-free (SAFE) diazo transfer and Rh2(esp)2-catalyzed cycloaddition of the resulting 5-diazobarbituric acids with aliphatic and aromatic nitriles. Besides being shorter compared to the previously described approaches, the method allows introduction of alkyl substituents at the 1,3-oxazole ring of the fused heterocyclic system.Graphical abstractGraphical abstract for this article
       
  • Irreversible aldolization of ketones with bisdicyclohexylboron enediolates
    • Abstract: Publication date: Available online 5 September 2019Source: Tetrahedron LettersAuthor(s): P. Veeraraghavan Ramachandran, Barnabas Otoo Unlike the reported reversible addition of ketone enolborinates to ketones, the aldolization of ketones with bisboron enediolates derived from carboxylic acids proceeds without difficulty. A variety of α,β,β-trisubstituted-β-hydroxy acids have been thus synthesized in good to excellent yields and diastereoselectivities.Graphical abstractGraphical abstract for this article
       
  • Total synthesis of Violaceimides A-E and consideration of the reported
           stereochemistry
    • Abstract: Publication date: Available online 4 September 2019Source: Tetrahedron LettersAuthor(s): Charles K. Perry, Mark G. Fulton, Craig W. Lindsley Here we report the first total synthesis of violaceimides A-E, a family of sulfur-containing metabolites from Aspergillus violaceus, a sponge-associated fungus. A concise, convergent and enantioselective synthesis was developed for all five family members, from a common advanced intermediate. However, while the NMR spectral data matched that of the reported natural products, the optical rotations were of opposite sign. This result prompted the enantioselective synthesis of all four diastereomeric pairs of violaceimide E, and suggests that the stereochemistry might have been misassigned.Graphical abstractGraphical abstract for this article
       
  • Synthesis of Isoindolinones : Intramolecular [4+2] Cycloaddition / Retro
           [4+2] of Pyridone Propiolamides
    • Abstract: Publication date: Available online 4 September 2019Source: Tetrahedron LettersAuthor(s): Jonathan E. Wilson, Joshua Garvey, Kennedy M. Taveras A new synthesis of isoindolinones was discovered during a screening campaign aimed at the development of novel methods for the synthesis of pyridone-EZH2 inhibitor analogues. The reaction proceeds via an intramolecular [4+2] cycloaddition of a pyridone with a tethered propiolamide moiety followed by extrusion of isocyanic acid. The discovery, optimization, and scope of the methodology are described.Graphical abstractGraphical abstract for this article
       
  • Convenient entry to N-pyridinylureas with pharmaceutically privileged
           oxadiazole substituents via the acid-catalyzed C–H activation of
           N-oxides
    • Abstract: Publication date: Available online 4 September 2019Source: Tetrahedron LettersAuthor(s): Kirill Geyl, Sergey Baykov, Marina Tarasenko, Lev E. Zelenkov, Vladislava Matveevskaya, Vadim P. Boyarskiy Pyridine-N-oxides bearing a pharmacophoric oxadiazole moiety could be C–H functionalized via the acid-catalyzed reaction with dialkylcyanamides, providing access to hitherto undescribed pyridine-2-yl substituted ureas, which have potential as “lead-like” scaffolds for medicinal chemistry. Atom-economy, environmental friendliness (no halide-containing or toxic reagents), simple work-up, as well as scalability are the main advantages of the employed procedure.Graphical abstractGraphical abstract for this article
       
  • A general, enantioselective synthesis of 2-substituted thiomorpholines and
           thiomorpholine 1,1-dioxides
    • Abstract: Publication date: Available online 3 September 2019Source: Tetrahedron LettersAuthor(s): Carson W. Reed, Craig W. Lindsley In the course of our drug discovery programs, we had need to access chiral, 2-substituted thiomorpholines and their oxidized congeners, thiomorpholine 1,1-dioxides. Here, we disclose a high-yielding, general protocol for the enantioselective synthesis of C2-functionlized thiomorpholines and thiomorpholine 1,1-dioxides.Graphical abstractGraphical abstract for this article
       
  • Efficient Synthesis of N- and O-linked Glycopeptides using Acid-Labile Boc
           Groups for the Protection of Carbohydrate Moieties
    • Abstract: Publication date: Available online 3 September 2019Source: Tetrahedron LettersAuthor(s): Tomohiro Tanaka, Mika Shiraishi, Akio Matsuda, Mamoru Mizuno Development of a synthetic method for the preparation of homogeneous glycopeptides and glycoproteins is important for the elucidation of their structures and functions. Here, we report on the concise and facile synthesis of glycopeptides using Boc groups for the protection of carbohydrate hydroxyl groups. This method enables us to remove the protecting groups from peptide and carbohydrate moieties in a single-step process without undesirable any side reaction.Graphical abstractGraphical abstract for this article
       
  • Synthesis of dialkoxydiphenylsilanes via the rhodium-catalyzed
           hydrosilylation of aldehydes
    • Abstract: Publication date: Available online 31 August 2019Source: Tetrahedron LettersAuthor(s): Christophe Nogues, Gilles Argouarch The commercially available rhodium(I) complex [RhCl(CO)2]2 (1) was shown to be an effective catalyst for the reduction of carbonyls with organosilanes under mild conditions. This study focusses on the hydrosilylation of aldehydes with diphenylsilane leading to the isolation of a series of dialkoxydiphenylsilanes with low catalytic loading of complex 1.Graphical abstractGraphical abstract for this article
       
  • Ru(II)-catalyzed α-sulfonamidation of cyclic β-ketoesters with
           sulfonyl azides
    • Abstract: Publication date: Available online 31 August 2019Source: Tetrahedron LettersAuthor(s): M.V. Krishna Rao, K. Nagarjuna Reddy, B. Sridhar, B.V. Subba Reddy α-Sulfonamidation of β-ketoesters with sulfonyl azide has been developed for the first time using a catalytic amount of Ru(II) complex to produce the 1-oxo-2-(sulfonamido)-2,3-dihydro-1H-indene-2-carboxylate and 1-oxo-2-(sulfonamido)-1,2,3,4-tetrahydronaphthalene-2-carboxylate derivatives in good yields. This method also works well with α-iodotetralones to afford the N-(1,4-dioxo-1,4-dihydronaphthalen-2-yl)sulphonamide derivatives under similar conditions.Graphical abstractGraphical abstract for this article
       
  • Divergent synthesis of (quinoxalin-2-yl)-1,3-oxazines and
           pyrimido[1,6-a]quinoxalines via the cycloaddition reaction of
           acyl(quinoxalinyl)ketenes
    • Abstract: Publication date: Available online 29 August 2019Source: Tetrahedron LettersAuthor(s): Svetlana Kasatkina, Ekaterina Stepanova, Maksim Dmitriev, Ivan Mokrushin, Andrey Maslivets A facile synthetic approach towards two distinct quinoxaline-based heterocyclic scaffolds has been developed from the cycloaddition of acyl(quinoxalinyl)ketenes with carbodiimides. The described reaction represents the first example of a divergent synthesis based on acyl(quinoxalinyl)ketenes providing (quinoxalin-2-yl)-1,3-oxazines or pyrimido[1,6-a]quinoxalines depending on the type of the acyl substituent in the ketenes. The key reactants, acyl(quinoxalinyl)ketenes, are generated in situ via the thermal decarbonylation of readily available pyrroloquinoxaline oxo-derivatives. The proposed diversity-oriented synthesis provides facile access to a library of skeletally diverse pharmaceutically interesting quinoxaline-based heterocycles from inexpensive reagents.Graphical abstractGraphical abstract for this article
       
  • Cascade reactions for constructing heterocycles containing a
           pyrimidino-pyrazino-pyrimidine core using 1,2,4-triazole scaffolds
    • Abstract: Publication date: Available online 28 August 2019Source: Tetrahedron LettersAuthor(s): Dmytro M. Khomenko, Roman O. Doroshchuk, Ilona V. Raspertova, Jesús García López, Fernando López Ortiz, Sergiu Shova, Oleg A. Iegorov, Rostyslav D. Lampeka The regioselective cyclocondensation of aminoethyl-1,2,4-triazoles and glyoxal provides pentacyclic heterocycles in which two 7,8-dihydro-5H-6λ2-[1,2,4]triazolo[1,5-c]pyrimidine systems are connected through CH(OH) bridges generating a central piperazine-2,5-diol ring. The structure of the new compounds was elucidated based on 1H, 13C and 15N NMR spectroscopic methods. The molecular structure of the parent compound generated from aminoethyl-1,2,4-triazole was established by single crystal X-ray diffraction.Graphical abstractGraphical abstract for this article
       
  • One-pot approach to access 2H-pyran-2-ones bearing an amino group via the
           Pd-catalyzed Sonogashira coupling of (Z)-3-iodovinylic esters followed by
           intramolecular iodocyclization
    • Abstract: Publication date: Available online 28 August 2019Source: Tetrahedron LettersAuthor(s): Atef Mayooufi, Moufida Romdhani-Younes, Johan Jacquemin, Jérôme Thibonnet A one‐pot sequence of Sonogashira coupling and iodocyclization afforded novel amino-containing trisubstituted 2H-pyran-2-ones in good yields. This transformation proceeds via 1) synthesis of an ynenoic ester intermediate by a Sonogashira coupling reaction with an N-substituted (Z)-3-iodovinylic ester; 2) intramolecular iodocyclization of the latter intermediate under mildly basic conditions. The flexibility of this strategy enables the efficient syntheses of a variety of substituted 2H-pyran-2-ones.Graphical abstractGraphical abstract for this article
       
  • Novel protection of 1,2-diol for trans-dihydroxycyclopentene ring
           construction by the C–H insertion of alkylidene carbene: formal total
           synthesis of (+)-trehazolin
    • Abstract: Publication date: Available online 27 August 2019Source: Tetrahedron LettersAuthor(s): Susumu Ohira, Atsuhito Kuboki, Yoshimi Takimoto, Kyosuke Matsuda, Saori Itasaki, Yuki Urushibata, Yoshiyuki Takano, Yuuki Nakamura The chiral vicinal diol was protected as 6-methylene-1,4-dioxepane to construct a cyclopentene ring by the C–H insertion of alkylidene carbene. The removal of the protecting group was achieved in a few steps, affording the corresponding diol in a reasonable yield. Using these reactions, the known synthetic intermediate for (+)-trehazolin was synthesized from D-diethyl tartrate. In addition, a short route to the intermediate from a D-mannitol derivative was described.Graphical abstractGraphical abstract for this article
       
  • Ruthenium-catalyzed selective hydrosilylation reaction of
           allyl-functionalized PEG derivatives
    • Abstract: Publication date: Available online 27 August 2019Source: Tetrahedron LettersAuthor(s): Koya Inomata, Yuki Naganawa, Haiqing Guo, Kazuhiko Sato, Yumiko Nakajima Reactions of allyl-functionalized poly(ethylene glycol) (PEG) derivatives with alkoxysilanes proceeded efficiently to furnish the corresponding hydrosilylated products in good to excellent yields using a ruthenium catalyst, [RuCl2(nbd)]n. A preliminary mechanistic study supported the pivotal role of the PEG moiety, which coordinated to the ruthenium atom during the reaction to achieve high reaction selectivity. This method may be applicable to the synthesis of various PEGs with a silyl terminus, which is useful as biocompatible and low toxic silane coupling agents..Graphical abstractGraphical abstract for this article
       
  • A simple synthesis of ketone from carboxylic acid using tosyl chloride as
           an activator
    • Abstract: Publication date: Available online 27 August 2019Source: Tetrahedron LettersAuthor(s): Debasis Sahoo, Sohini Sarkar, Samaresh Jana An effective process for the conversion of carboxylic acid to ketone has been discovered. In this process, carboxylic acid has been activated using p-toluene sulphonyl group. Under the optimized condition, aromatic, aliphatic heteroaromatic carboxylic acids have been proved to be good substrates for this methodology. The byproduct of this reaction can be removed very easily during work up process. Also, one equivalent of organometallic reagent is sufficient to complete this transformation.Graphical abstractGraphical abstract for this article
       
  • Iridium-catalyzed Intramolecular C–N and C–O/S Cross-Coupling
           Reactions: Preparation of Benzoazole Derivatives
    • Abstract: Publication date: Available online 26 August 2019Source: Tetrahedron LettersAuthor(s): Yajie Shi, Qifan Zhou, Fangyu Du, Yang Fu, Yang Du, Ting Fang, Guoliang Chen The irdium-catalyzed intramolecular arylcarbon-hetero cross-coupling reactions with o-haloarylamides or o-haloarylamidine have been effectively achieved using KOAc and just 1 mol % catalyst. The [Ir(cod)Cl]2 was proved to be more potential for smoothly assembling functional structures benzimidazoles, benzoxazoles and benzothiazoles, which was superior to Cu- and Pd-catalyzed systems. Simultaneously, a concise and efficient synthesis of tafamidis was developed in 5-gram scale.Graphical abstractGraphical abstract for this article
       
  • Photochemical Reaction of Anthracene with Dioxygen Catalyzed by
           Platinum(II) Porphyrin
    • Abstract: Publication date: Available online 24 August 2019Source: Tetrahedron LettersAuthor(s): Ken-ichi Yamashita, Ken-ichi Sugiura Visible light irradiation of anthracene in the presence of platinum(II) porphyrin (PtPor) and dioxygen affords anthraquinone as the main product. This reaction involves two steps: the [4+2]cycloaddition of anthracene with singlet oxygen to afford anthracene-9,10-endoperoxide and the degradation of endoperoxide. PtPor catalyzes both reactions.Graphical abstractGraphical abstract for this article
       
  • Unexpected photochemical transformation of imidazole derivatives
           containing the 5-hydroxy-2-methyl-4H-pyran-4-one moiety. Environmentally
           friendly method for the synthesis of substituted
           imidazo[1,5-a]pyridine-5,8-diones
    • Abstract: Publication date: Available online 24 August 2019Source: Tetrahedron LettersAuthor(s): Valeriya G. Melekhina, Andrey N. Komogortsev, Boris V. Lichitsky, Vitaly S. Mityanov, Artem N. Fakhrutdinov, Arkadii A. Dudinov, Vasily A. Migulin, Yulia V. Nelyubina, Elizaveta K. Melnikova, Michail M. Krayushkin An unexpected photochemical transformation of imidazole derivatives containing the 5-hydroxy-2-methyl-4H-pyran-4-one moiety was discovered, which led to the synthesis of previously unknown imidazo[1,5-a]pyridine-5,8-dione derivatives. The structures of imidazole and imidazo[1,5-a]pyridine-5,8-dione derivatives were unambiguously determined by X-ray diffraction analysis.Graphical abstractGraphical abstract for this article
       
  • One-pot synthesis of new iso-DPP derivatives from terminal
           alkynes and isocyanates
    • Abstract: Publication date: Available online 24 August 2019Source: Tetrahedron LettersAuthor(s): Jonathan Guild, Michael J. Morris, Craig C. Robertson, Alexander W.H. Speed The reaction of phenyl acetylide anion with aryl isocyanates followed by quenching with water is shown to produce pyrrolopyrrole (iso-DPP) derivatives in addition to the isomeric cyclopentadienone imines previously reported. If the reaction is quenched with dilute HCl, 5-ylidenepyrrol-2(5H)-ones, formed by a Meyer-Schuster rearrangement, can be isolated instead. A possible mechanism for this reaction is suggested.Graphical abstractGraphical abstract for this article
       
  • Synthesis and NMR spectroscopic assignment of chlorinated
           benzimidazole-2-thione derivatives
    • Abstract: Publication date: Available online 23 August 2019Source: Tetrahedron LettersAuthor(s): Matic Proj, Izidor Sosič, Stanislav Gobec The benzimidazole-2-thione scaffold is present in many drugs encompassing various therapeutic areas. Due to the broad spectrum of bioactivities it also represents an important starting point in drug discovery campaigns, especially those based on fragment-based design. Despite simple structures the tautomerism and regioisomerism of substituted benzimidazole-2-thiones makes unambiguous structural analysis difficult. Tautomeric duplicates are present in commercial libraries resulting in two tautomers being sold as different products. To showcase an example of appropriate structural determination, we synthesized and characterized a set of benzimidazole-2-thiones with different positions of a chlorine atom on the ring. Using NOESY and 13C NMR spectroscopy, we determined that the thione tautomer predominates in the thione-thiol equilibrium. Furthermore, NOESY and HMBC experiments confirmed the position of the substituents on the benzimidazole-2-thione ring.Graphical abstractGraphical abstract for this article
       
  • Palladium-catalyzed Intramolecular C–H Acylation of Indoles with
           Thioester
    • Abstract: Publication date: Available online 23 August 2019Source: Tetrahedron LettersAuthor(s): Min Liu, Yu-Wen Liu, Hui Xu, Hui-Xiong Dai A palladium-catalyzed intramolecular C–H acylation of indole with thioester is described, providing a direct and effective approach for the synthesis of the biologically active indole-indolone scaffolds. The method obviates the need for the prefunctionalized starting materials including organometallic reagents, alkyl halides, and NHP esters in previous metal-catalyzed cross-coupling reaction with thioester. Substrates bearing sensitive halo groups are compatible in the reaction, leaving a functional handle for further structural elaborations.Graphical abstractGraphical abstract for this article
       
  • Base promoted peroxide systems for the efficient synthesis of nitroarenes
           and benzamides
    • Abstract: Publication date: Available online 22 August 2019Source: Tetrahedron LettersAuthor(s): Sampa Gupta, Alisha Ansari, Koneni V. Sashidhara A useful and efficient approach for the synthesis of nitroarenes from several aromatic amines (including heterocycles) using peroxide and base has been developed. This oxidative reaction is very easy to handle and afforded the products in good yields. Formation of benzamides from benzylamine was also successfully carried out with this metal-free catalytic system in good to excellent yields.Graphical abstractGraphical abstract for this article
       
  • Benzothiazole-based heterodipodal chemosensor for Cu2+ and CN- ions in
           aqueous media
    • Abstract: Publication date: Available online 22 August 2019Source: Tetrahedron LettersAuthor(s): Won Sik Na, Pushap Raj, Narinder Singh, Doo Ok Jang A simple and selective chemosensor, A, was developed for recognizing Cu2+. The emission spectra of receptor A showed a fluorescence quenching response upon addition of Cu2+ with a low detection limit of 4.51 nM, significantly less than the WHO recommended guideline for drinking water. In addition, the formed A∙Cu2+ complex was examined for secondary sensing of anions. The A∙Cu2+ complex showed selectivity for CN- via a recovering emission profile of A.Graphical abstractGraphical abstract for this article
       
  • Copper-Catalyzed Remote C-H Monofluoromethylation of 8-Aminoquinolines
           with Dimethyl Phosphonate as Reductant
    • Abstract: Publication date: Available online 22 August 2019Source: Tetrahedron LettersAuthor(s): Shuaijun Han, Qingsong Wu, Lucas Mele, Licheng Ding, Jingya Li, Dapeng Zou, Yusheng Wu, Yangjie Wu A simple and efficient copper-catalyzed monofluoromethylation of 8-aminoquinolines with 2-bromo-2-fluoroacetate has been described with HPO(OMe)2 (dimethyl phosphonate) as reductant. The reaction tolerates a variety of quinoline amides and monofluoroalkyl bromides. Significant advantages of this protocol include synthetic convenience and high reaction efficiency.Graphical abstractGraphical abstract for this article
       
  • A highly efficient and stereoselective cycloaddition of nitrones to
           N-arylitaconimides
    • Abstract: Publication date: Available online 21 August 2019Source: Tetrahedron LettersAuthor(s): Polina S. Teterina, Mariia M. Efremova, Ekaterina V. Sirotkina, Alexander S. Novikov, Olesya V. Khoroshilova, Alexander P. Molchanov The 1,3-dipolar cycloaddition of keto- and aldonitrones with N-arylitaconimides proceeds regioselectively giving only 5-spiroisoxazolidines. In the case of aldonitrones the reaction proceeds with high diastereoselectivity. A range of the obtained adducts were subjected to reductive cleavage of the NO bond using zinc powder in acetic acid to give the corresponding spirolactones and 1,3-amino alcohols.Graphical abstractGraphical abstract for this article
       
  • Recent advances in Gomberg-Backmann biaryl synthesis
    • Abstract: Publication date: Available online 20 August 2019Source: Tetrahedron LettersAuthor(s): Toru Amaya, Yuqing Jin, Mamoru Tobisu The Gomberg-Bachmann reaction is an intermolecular aryl-aryl cross-coupling reaction using an arenediazonium salt and an arene. This digest review surveys recent advances in the Gomberg-Bachmann reaction. More specifically, it focuses on reaction systems that include 1) transition-metal-induced systems, 2) organic promoter-induced systems, 3) electrolytic systems, 4) photoredox systems, and 5) hybrid systems that involve photoredox and transition-metal catalysts.Graphical abstractGraphical abstract for this article
       
  • Influence of microwave irradiation on DNA hybridization and polymerase
           reactions
    • Abstract: Publication date: Available online 19 August 2019Source: Tetrahedron LettersAuthor(s): Jinyu Sun, Jesse Vanloon, Hongbin Yan We report herein that exposure of DNA to microwave irradiation at constant temperature leads to faster strand exchange, as compared with same experiments carried out in a water bath at the same temperature. Furthermore, polymerase chain reactions carried out under microwave irradiation were faster than those in a water bath at the same temperature as well. While the causes of these differences are unclear at this time, this research suggests that microwave irradiation can lead to subtle changes in DNA structural dynamics and functions.Graphical abstractGraphical abstract for this article
       
  • A Practical Method for Preparation of Phenols from Arylboronic Acids
           Catalyzed by Iodopovidone in Aqueous Medium
    • Abstract: Publication date: Available online 12 June 2019Source: Tetrahedron LettersAuthor(s): Guangying Lu, Yaoyao Ren, Bin Dong, Bin Zhou, Jiangmeng Ren, Yanxiong Ke, Bu-Bing Zeng A novel and efficient strategy for the ipso-hydroxylation of arylboronic acids to phenols has been developed using inexpensive, readily available, air-stable water-soluble povidone iodine as catalyst and aqueous hydrogen peroxide as oxidizing agent. The reactions were performed at room temperature under metal-, ligand- and base-free condition in a short reaction time. The corresponding substituted phenols were obtained in moderate to good yields by oxidative hydroxylation of arylboronic acids in aqueous medium.Graphical abstractGraphical abstract for this article
       
  • Catalytic Removal of tert-Butyldimethylsilyl (TBS) ether by PVP-I
    • Abstract: Publication date: Available online 29 May 2019Source: Tetrahedron LettersAuthor(s): Guangying Lu, Di Wang, Jiangmeng Ren, Yanxiong Ke, Bu-Bing Zeng A mild, efficient and rapid protocol the deprotection of alcoholic TBDMS ethers using PVP-1 as catalyst in methanol, the procedure of deprotection of various TBDMS ethers were found to be very convenient, easy work-up, high yielding.Graphical abstractGraphical abstract for this article
       
  • A novel metal-free synthesis of thiazole-substituted α-hydroxy carbonyl
           compounds and 2-alkenylthiazoles from thiazole N-oxides and olefins
    • Abstract: Publication date: Available online 28 May 2019Source: Tetrahedron LettersAuthor(s): Hui Li, Juan Zhang, Yanqiu Zhang, Jiayi Wang, Gonghua Song A metal-free and highly atom-economic synthesis of thiazole-substituted α-hydroxy carbonyl compounds has been developed. Catalyzed by 5 mol% of p-toluenesulfonic acid (TsOH), a variety of thiazole-substituted α-hydroxy carbonyl compounds were obtained in moderate to good yields via 1,3-dipolar cycloaddition of thiazole N-oxides with olefins, followed by a ring-opening reaction. Furthermore, the corresponding 2-alkenylthiazoles could be produced in excellent yields from synthesized α-hydroxy carbonyl compounds through a one-pot, two-step dehydration process.Graphical abstractA metal-free and highly atom-economic synthesis of thiazole-substituted α-hydroxy carbonyl compounds has been developed. Catalyzed by 5 mol% of p-toluenesulfonic acid (TsOH), a variety of thiazole-substituted α-hydroxy carbonyl compounds were obtained in moderate to good yields via 1,3-dipolar cycloaddition of thiazole N-oxides with olefins, followed by a ring-opening reaction. Furthermore, the corresponding 2-alkenylthiazoles could be produced in excellent yields from synthesized α-hydroxy carbonyl compounds through a one-pot, two-step dehydration process.Graphical abstract for this article
       
  • Triphenylamine or carbazole-based benzothiadiazole luminophors with
           remarkable solvatochromism and different mechanofluorochromic behaviors
    • Abstract: Publication date: Available online 22 July 2019Source: Tetrahedron LettersAuthor(s): Hai-feng He, Xuan-tao Shao, Li-li Deng, Jia-xin Zhou, Yuan-yuan Zhu, Hong-ying Xia, Liang Shen, Feng Zhao Two triphenylamine or carbazole-based benzothiadiazole luminophors have been successfully synthesized and characterized. Interestingly, both the donor-acceptor-donor (D-A-D) type compounds 1 and 2 exhibited remarkable solvatochromism behavior. In addition, luminogen 1 showed reversible mechanochromism phenomenon involving red-shifted fluorescent color transformation from yellow to red. However, luminogen 2 showed switchable mechanochromism behavior involving blue-shifted fluorescent color change from yellow to yellow-green.Graphical abstractGraphical abstract for this article
       
  • Unique protonation behavior of cationic free-base porphyrins in the
           interlayer space of transparent solid films comprising layered
           α-zirconium phosphate
    • Abstract: Publication date: Available online 3 July 2019Source: Tetrahedron LettersAuthor(s): Yu-hei Aoyama, Takuya Fujimura, Ryo Sasai The protonation behavior of α,β,γ,δ-tetrakis(1-methylpyridinium-4-yl)porphyrin (H2TMPyP) in the interlayer space of transparent solid films comprising layered α-zirconium phosphate was investigated. It was found that the exposure of H2TMPyP-impregnated films to aqueous HCl resulted in pyrrole group protonation and induced a color change from yellow to greenish yellow. The two pKa values of H2TMPyP, determined as 2.4 and 2.6, exceeded those determined in aqueous solution (0.80 and 2.06), which was attributed to the condensation of H+ in the interlayer space caused by the cation exchange reaction between H+ in the aqueous solution and n-butylamine intercalated in the interlayer space.Graphical abstractGraphical abstract for this article
       
 
 
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