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Hiroyuki Ishibashi - One of the best experts on this subject based on the ideXlab platform.
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8-ENDO-SELECTIVE ARYL Radical Cyclization LEADING TO
2016Co-Authors: Tsuyoshi Taniguchi, Hisaaki Zaimoku, Hiroyuki IshibashiAbstract:Abstract – Bu3SnH-mediated Radical Cyclization of N-acyl-3-(2-bromophenyl)-N-ethenypropylamines (14) occurred in an endo-selective manner to give the 3-benzazocine derivatives (15) in good yields
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is an iodine atom almighty as a leaving group for bu3snh mediated Radical Cyclization the effect of a halogen atom on the 5 endo trig Radical Cyclization of n vinyl α halo amides
Journal of Organic Chemistry, 2002Co-Authors: Osamu Tamura, Yoshifumi Takeda, Hana Matsukida, Atsushi Toyao, Hiroyuki IshibashiAbstract:The effect of a halogen atom as a leaving group on Bu(3)SnH-mediated 5-endo-trig Radical Cyclization of N-(cyclohex-1-enyl) alpha-halo amides was examined. The Cyclization of alpha-chloro amides occurred with a high degree of efficiency, whereas the corresponding alpha-iodo congeners gave only limited quantities of Cyclization products. A detailed study revealed that these phenomena could be attributed to the initial conformations of alpha-halo amides. The cyclizing ability of alpha-iodo amides can be restored with Bu(3)SnCl or Bu(3)SnF as an additive. The Cyclization of an alpha-iodo amide in the presence of Bu(3)SnF could be applied to a short-step synthesis of lycoranes featuring sequential 5-endo-trig and 6-endo-trig Radical Cyclizations.
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synthesis of a model compound of mappicine ketone based on sulfur directed 5 exo selective aryl Radical Cyclization onto enamides
ChemInform, 2001Co-Authors: Hiroyuki Ishibashi, Issei Kato, Yoshifumi Takeda, Osamu TamuraAbstract:Enamides 10, upon treatment with Bu3SnH–AIBN, gave 5-exo aryl Radical Cyclization products 11, which were partially desulfurized to give 1-substituted dihydroisoindoles 7 and 12. This method was applied to the synthesis of a model compound 4 of mappicine ketone (1).
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regiochemistry in aryl Radical Cyclization onto methylenecycloalkanes
Journal of Organic Chemistry, 2000Co-Authors: Hiroyuki Ishibashi, Tetsuya Kobayashi, Sayaka Nakashima, Osamu TamuraAbstract:Bu(3)SnH-mediated aryl Radical Cyclization onto methylenecycloalkanes having a phenylthio, an ester, or a nitrile group at the terminus of the alkenic bond provides exclusively exo Cyclization products. The results are in sharp contrast to those reported for nonsubstituted methylenecycloalkanes, which give exclusively endo Cyclization products. Formation of endo Cyclization products has been suggested to be a result of a consecutive 5-exo Cyclization of an aryl Radical and neophyl rearrangement. The exo-selective aryl Radical Cyclization offers a new method for synthesizing fused aromatic compounds containing a benzylic quaternary carbon atom.
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a new efficient route to physostigmine and physovenine by means of 5 exo selective aryl Radical Cyclization of o bromo n acryloylanilides
Tetrahedron, 2000Co-Authors: Hiroyuki Ishibashi, Tetsuya Kobayashi, Noriko Machida, Osamu TamuraAbstract:Abstract Bu3SnH-mediated aryl Radical Cyclization of o-bromo-N-acryloylanilides 16 and 17 proceeded in a 5-exo manner exclusively to give, in high yields, oxindoles 3 and 4, the key intermediates for the synthesis of (±)-physostigmine and (±)-physovenine, respectively.
Osamu Tamura - One of the best experts on this subject based on the ideXlab platform.
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is an iodine atom almighty as a leaving group for bu3snh mediated Radical Cyclization the effect of a halogen atom on the 5 endo trig Radical Cyclization of n vinyl α halo amides
Journal of Organic Chemistry, 2002Co-Authors: Osamu Tamura, Yoshifumi Takeda, Hana Matsukida, Atsushi Toyao, Hiroyuki IshibashiAbstract:The effect of a halogen atom as a leaving group on Bu(3)SnH-mediated 5-endo-trig Radical Cyclization of N-(cyclohex-1-enyl) alpha-halo amides was examined. The Cyclization of alpha-chloro amides occurred with a high degree of efficiency, whereas the corresponding alpha-iodo congeners gave only limited quantities of Cyclization products. A detailed study revealed that these phenomena could be attributed to the initial conformations of alpha-halo amides. The cyclizing ability of alpha-iodo amides can be restored with Bu(3)SnCl or Bu(3)SnF as an additive. The Cyclization of an alpha-iodo amide in the presence of Bu(3)SnF could be applied to a short-step synthesis of lycoranes featuring sequential 5-endo-trig and 6-endo-trig Radical Cyclizations.
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synthesis of a model compound of mappicine ketone based on sulfur directed 5 exo selective aryl Radical Cyclization onto enamides
ChemInform, 2001Co-Authors: Hiroyuki Ishibashi, Issei Kato, Yoshifumi Takeda, Osamu TamuraAbstract:Enamides 10, upon treatment with Bu3SnH–AIBN, gave 5-exo aryl Radical Cyclization products 11, which were partially desulfurized to give 1-substituted dihydroisoindoles 7 and 12. This method was applied to the synthesis of a model compound 4 of mappicine ketone (1).
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regiochemistry in aryl Radical Cyclization onto methylenecycloalkanes
Journal of Organic Chemistry, 2000Co-Authors: Hiroyuki Ishibashi, Tetsuya Kobayashi, Sayaka Nakashima, Osamu TamuraAbstract:Bu(3)SnH-mediated aryl Radical Cyclization onto methylenecycloalkanes having a phenylthio, an ester, or a nitrile group at the terminus of the alkenic bond provides exclusively exo Cyclization products. The results are in sharp contrast to those reported for nonsubstituted methylenecycloalkanes, which give exclusively endo Cyclization products. Formation of endo Cyclization products has been suggested to be a result of a consecutive 5-exo Cyclization of an aryl Radical and neophyl rearrangement. The exo-selective aryl Radical Cyclization offers a new method for synthesizing fused aromatic compounds containing a benzylic quaternary carbon atom.
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a new efficient route to physostigmine and physovenine by means of 5 exo selective aryl Radical Cyclization of o bromo n acryloylanilides
Tetrahedron, 2000Co-Authors: Hiroyuki Ishibashi, Tetsuya Kobayashi, Noriko Machida, Osamu TamuraAbstract:Abstract Bu3SnH-mediated aryl Radical Cyclization of o-bromo-N-acryloylanilides 16 and 17 proceeded in a 5-exo manner exclusively to give, in high yields, oxindoles 3 and 4, the key intermediates for the synthesis of (±)-physostigmine and (±)-physovenine, respectively.
Debankan Ghosh - One of the best experts on this subject based on the ideXlab platform.
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Thiophenol mediated Radical Cyclization: an expedient approach to 2H-pyrrolo[3,2-d]pyrimidines (9-deazaxanthine analogs)
Tetrahedron Letters, 2010Co-Authors: Krishna C. Majumdar, Shovan Mondal, Debankan GhoshAbstract:A new efficient route for the synthesis of substituted 2H-pyrrolopyrimidines (9-deazaxanthine analogs) via thiophenol mediated Radical Cyclization has been achieved. The stereochemistry of the newly synthesised compounds has been settled from NOE data.
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An easy access to pyrimidine-fused azocine derivatives by thiophenol-mediated Radical Cyclization via 8-endo-trig mode
Tetrahedron Letters, 2010Co-Authors: Krishna C. Majumdar, Shovan Mondal, Debankan GhoshAbstract:Abstract An efficient route for the synthesis of eight-membered nitrogen heterocycles has been developed via a thiophenol-mediated intramolecular 8-endo-trig Radical Cyclization. The Radical precursors were prepared using BF3·Et2O-catalyzed aza-Claisen rearrangement followed by the reaction with propargyl bromide. The alkenyl Radicals are generated from thiophenol initiated by the benzoyl peroxide instead of commonly used AIBN for easy and facile isolation of the pure products.
Chengjian Zhu - One of the best experts on this subject based on the ideXlab platform.
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copper catalyzed cascade phosphorylation initiated Radical Cyclization access to 2 phosphorylated pyrrolo 1 2 a indole
Journal of Organic Chemistry, 2017Co-Authors: Honglin Zhang, Chengjian ZhuAbstract:A copper-catalyzed tandem Radical Cyclization of 1-(3-phenylprop-2-yn-1-yl)-1H-indole with diphenylphosphine oxides was developed. C–P bond formation was achieved coupled with C(sp2)–H functionalization. It provided an access to construct the pyrrolo[1,2-a]indole motif and a series of 2-phosphinoyl-9H-pyrrolo[1,2-a]indoles.
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a novel visible light mediated Radical Cyclization of enol lactones a concise method for fluorinated polycyclic lactone scaffolds
Chemical Communications, 2015Co-Authors: Yixiang Cheng, Chengjian ZhuAbstract:A novel visible light mediated Radical Cyclization of enol lactones with difluoroacyl arenes is presented. The reaction experienced a tandem Radical Cyclization and tolerated a wide range of substrates, resulting in fluorinated γ-butyrolactones in good chemical yield and with excellent diastereoselectivity.
Hua Wang - One of the best experts on this subject based on the ideXlab platform.
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silver mediated Radical Cyclization of alkynoates and α keto acids leading to coumarins via cascade double c c bond formation
Journal of Organic Chemistry, 2015Co-Authors: Daoshan Yang, Fen Wang, Yuanyuan Shuai, Qiannan Li, Hua WangAbstract:A novel and convenient silver-mediated Radical Cyclization method for the synthesis of coumarin derivatives via the direct difunctionalization of alkynoates with α-keto acids through double C–C bond formation under mild conditions has been developed. This new method is highly efficient and practical, and the starting materials are readily prepared. The present method should provide a useful strategy for the construction of coumarin motifs.
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metal free n et4nbr catalyzed Radical Cyclization of disulfides and alkynes leading to benzothiophenes under mild conditions
RSC Advances, 2014Co-Authors: Daoshan Yang, Laijin Tian, Qinghe Li, Hua WangAbstract:A novel n-Et4NBr-catalyzed method for the synthesis of benzothiophene derivatives via cascade reactions of substituted disulfides with alkynes through S–S bond cleavage and alkenyl Radical Cyclization reactions has been developed. The reaction has a high functional-group tolerance. The new method is environmental and practical, and the starting materials are readily available. These advantages, relative to previous methods, provide an opportunity for the construction of diverse and useful benzothiophene motifs.
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metal free n et4nbr catalyzed Radical Cyclization of disulfides and alkynes leading to benzothiophenes under mild conditions
RSC Advances, 2014Co-Authors: Daoshan Yang, Laijin Tian, Qinghe Li, Hua WangAbstract:A novel n-Et4NBr-catalyzed method for the synthesis of benzothiophene derivatives via cascade reactions of substituted disulfides with alkynes through S–S bond cleavage and alkenyl Radical Cyclization reactions has been developed. The reaction has a high functional-group tolerance. The new method is environmental and practical, and the starting materials are readily available. These advantages, relative to previous methods, provide an opportunity for the construction of diverse and useful benzothiophene motifs.