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Hidetoshi Tokuyama - One of the best experts on this subject based on the ideXlab platform.
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Total Synthesis of (-)-Lepadiformine A via Radical Translocation-Cyclization Reaction.
Organic Letters, 2020Co-Authors: Masashi Shimomura, Manabu Sato, Hiroki Azuma, Juri Sakata, Hidetoshi TokuyamaAbstract:Total synthesis of (−)-lepadiformine A featuring construction of the 1-azaspiro[4.5]decane skeleton by a highly diastereoselective radical translocation–Cyclization Reaction of a γ-lactam derivativ...
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total synthesis of histrionicotoxin through a stereoselective radical translocation Cyclization Reaction
Angewandte Chemie, 2017Co-Authors: Manabu Sato, Hiroki Azuma, Kentaro Okano, Kiyosei Takasu, Akihiro Daigaku, Sota Sato, Hidetoshi TokuyamaAbstract:Stereoselective total syntheses of (−)-histrionicotoxin and (−)-histrionicotoxin 235A are described. The 1-azaspiro[5.5]undecane skeleton was constructed diastereoselectively by a radical translocation–Cyclization Reaction involving a chiral cyclic acetal; the use of tris(trimethylsilyl)silane was crucial for the high diastereoselectivity. The Cyclization product was converted into (−)-histrionicotoxin 235A through a one-pot partial-reduction–allylation Reaction of a derivative containing an unprotected lactam. Finally, two terminal alkenes were transformed into enynes with the 1,3-amino alcohol protected as an oxathiazolidine oxide to complete the total synthesis of (−)-histrionicotoxin.
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Total Synthesis of (±)-LepadiformineA via Radical Translocation-Cyclization Reaction
Synlett, 2010Co-Authors: Manabu Fujitani, Masami Tsuchiya, Kentaro Okano, Kiyosei Takasu, Masataka Ihara, Hidetoshi TokuyamaAbstract:A total synthesis of (±)-lepadiformine A was accomplished through construction of the 1-azaspiro[4.5]decane skeleton by a sequential radical translocation-Cyclization Reaction.
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Total Synthesis of (−)-Lepadiformine A viaRadical Translocation–Cyclization Reaction
1Co-Authors: Masashi Shimomura, Manabu Sato, Hiroki Azuma, Juri Sakata, Hidetoshi TokuyamaAbstract:Total synthesis of (−)-lepadiformine A featuring construction of the 1-azaspiro[4.5]decane skeleton by a highly diastereoselective radical translocation–Cyclization Reaction of a γ-lactam derivative bearing a chiral butenolide moiety is described. The enantioselective construction of butenolide is conducted via Krische’s catalytic asymmetric allylation protocol. After the radical translocation–Cyclization Reaction, a hydroxymethyl group at the C-13 position was stereoselectively introduced by a one-pot partial reduction–allylation protocol of the unprotected lactam derivative. Finally, the total synthesis is completed by formation of a C ring.
Anil K. Saikia - One of the best experts on this subject based on the ideXlab platform.
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Ene Cyclization Reaction in heterocycle synthesis.
Organic & Biomolecular Chemistry, 2018Co-Authors: Pipas Saha, Anil K. SaikiaAbstract:The ene Cyclization has evolved to become an indispensable tool for the synthesis of various ring size heterocyclic compounds. In the past and recent years, many exciting reports have demonstrated the broad scope and synthetic utility of ene Cyclization and the versatility of oxonium ion, iminium ion and thionium ion intermediates. Moreover, the ease of regio- and stereoselectivity of ene Cyclization has led to the development of new types of heterocyclic compounds. This article aims at reviewing the utilities of ene Cyclization Reactions for the synthesis of various ring sizes of oxygen, nitrogen and sulfur heterocycles. It also covers some applications in natural product synthesis. The mechanism of the Reactions is discussed wherever necessary. The review article covers the time period from 1986 to 2017.
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diastereoselective synthesis of substituted tetrahydrothiophenes and thiopyrans via thia prins Cyclization Reaction
Journal of Organic Chemistry, 2015Co-Authors: Madhurjya Borah, Paramartha Gogoi, Kiran Indukuri, Anil K. SaikiaAbstract:Tetrahydrothiophenes and -thiopyrans have been efficiently synthesized from thioacrylates via thia-Prins Cyclization Reaction mediated by trimethylsilyltrifluoromethanesulfonate with good diastereoselectivity and in good to high yields.
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Stereoselective Synthesis of Tetrahydroquinolines Through an Imino-Ene Cyclization Reaction
European Journal of Organic Chemistry, 2013Co-Authors: Somasekhar Bondalapati, Kiran Indukuri, Priya Ghosh, Anil K. SaikiaAbstract:heterocycles by using the oxonium-ene and thionium-ene Cyclization Reaction, respectively. Herein, we report amethodology for the synthesis of tetrahydroquinolines. TheReaction between an aldehyde and α-allylic aniline proceedsthrough an imino-ene Cyclization that is mediated by borontrifluoride–diethyl ether.
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diastereoselective synthesis of substituted dihydropyrans via an oxonium ene Cyclization Reaction
Organic and Biomolecular Chemistry, 2012Co-Authors: Pipas Saha, Sabera Sultana, Priya Ghosh, Anil K. SaikiaAbstract:Substituted dihydropyrans can be efficiently synthesized in good yields with excellent diastereoselectivity from the Reaction of aldehydes or epoxides and ethyl 3-alkyl-3-hydroxy-5-methylhex-5-enoate via an oxonium–ene Cyclization Reaction catalyzed by trimethylsilyl trifluoromethanesulfonate (TMSOTf) under mild conditions.
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Diastereoselective synthesis of substituted dihydropyrans via an oxonium–ene Cyclization Reaction
Organic and Biomolecular Chemistry, 2012Co-Authors: Pipas Saha, Sabera Sultana, Priya Ghosh, Anil K. SaikiaAbstract:Substituted dihydropyrans can be efficiently synthesized in good yields with excellent diastereoselectivity from the Reaction of aldehydes or epoxides and ethyl 3-alkyl-3-hydroxy-5-methylhex-5-enoate via an oxonium–ene Cyclization Reaction catalyzed by trimethylsilyl trifluoromethanesulfonate (TMSOTf) under mild conditions.
Martin Pettersson - One of the best experts on this subject based on the ideXlab platform.
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synthesis of pyridopyrazine 1 6 diones from 6 hydroxypicolinic acids via a one pot coupling Cyclization Reaction
Organic Letters, 2013Co-Authors: Tuan P Tran, Christopher Am W Ende, Patrick B Mullins, Martin PetterssonAbstract:A facile one-pot synthesis of 3,4-dihydro-1H-pyrido[1,2-a]pyrazine-1,6(2H)-diones (pyridopyrazine-1,6-diones) has been developed which employs a sequential coupling/Cyclization Reaction of 6-hydroxypicolinic acids and β-hydroxylamines. The transformation proceeds in good yield under mild conditions using O-(7-aza-1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HATU) to both carry out the amide formation and activate the hydroxyl group for intramolecular alkylation.
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Synthesis of pyridopyrazine-1,6-diones from 6-hydroxypicolinic acids via a one-pot coupling/Cyclization Reaction.
Organic Letters, 2013Co-Authors: Tuan P Tran, Patrick B Mullins, Christopher William Am Ende, Martin PetterssonAbstract:A facile one-pot synthesis of 3,4-dihydro-1H-pyrido[1,2-a]pyrazine-1,6(2H)-diones (pyridopyrazine-1,6-diones) has been developed which employs a sequential coupling/Cyclization Reaction of 6-hydroxypicolinic acids and β-hydroxylamines. The transformation proceeds in good yield under mild conditions using O-(7-aza-1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HATU) to both carry out the amide formation and activate the hydroxyl group for intramolecular alkylation.
Dengyu Xu - One of the best experts on this subject based on the ideXlab platform.
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visible light promoted dual c c bond formations of alkynoates via a domino radical addition Cyclization Reaction a synthesis of coumarins
Organic Letters, 2016Co-Authors: Shangbiao Feng, Weiwei Zhang, Zhuliang Zhong, Dengyu XuAbstract:A visible-light-promoted, mild, and direct difunctionalization of alkynoates has been accomplished. This procedure provides a new strategy toward synthesis of the coumarin core structure by photoredox-mediated oxidation to generate the α-oxo radical, which supervenes a domino radical addition/Cyclization Reaction in moderate to good yields with high regioselectivity at ambient temperature.
Weicheng Yuan - One of the best experts on this subject based on the ideXlab platform.
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highly efficient and stereocontrolled construction of 3 3 pyrrolidonyl spirooxindoles via organocatalytic domino michael Cyclization Reaction
ChemInform, 2013Co-Authors: Xiaomei Zhang, Weicheng YuanAbstract:Structurally diverse 3,3′-thiopyrrolidonyl spirooxindoles bearing three contiguous stereogenic centers can be smoothly prepared via domino Michael/Cyclization Reaction using quinine as chiral catalyst.
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highly efficient and stereocontrolled construction of 3 3 pyrrolidonyl spirooxindoles via organocatalytic domino michael Cyclization Reaction
Organic Letters, 2013Co-Authors: Xiaomei Zhang, Weicheng YuanAbstract:A wide range of structurally diverse 3,3′-thiopyrrolidonyl spirooxindoles bearing three contiguous stereogenic centers can be smoothly obtained via a domino Michael/Cyclization Reaction between 3-isothiocyanato oxindoles and 3-methyl-4-nitro-5-alkenyl-isoxazoles with commercially available quinine as the catalyst under mild conditions. The protocol is significantly characterized by high reactivity, a low catalyst loading (1 mol %), and an excellent diastereo- and enantioselectivity (up to >99:1 dr and 98% ee).
