The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Tohru Fukuyama - One of the best experts on this subject based on the ideXlab platform.
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Total Syntheses of Lyconadins A–C
2016Co-Authors: Takuya Nishimura, Satoshi Yokoshima, Aditya K. Unni, Tohru FukuyamaAbstract:The total synthesis of the Lycopodium alkaloid lyconadin A was accomplished and it was applied to the total syntheses of the related congeners, lyconadins B and C. Lyconadin A has attracted attention as a challenging target for total synthesis due to the unprecedented pentacyclic skeleton. Our synthesis of lyconadin A features a facile construction of the highly fused tetracyclic skeleton through a combination of an aza-Prins reaction and an electrocyclic ring opening, followed by formation of a C–N bond. Transformation of the Bromoalkene moiety of the tetracycle to a key enone intermediate was extensively investigated, and three methods via sulfide, oxime, or azide intermediates were established. A pyridone ring was constructed from the key enone intermediate to complete the synthesis of lyconadin A. A dihydropyridone ring could also be formed from the same enone intermediate, leading to a synthesis of lyconadin B. Establishment of the conditions for an electrocyclic ring opening without formation of the C–N bond resulted in completion of the total synthesis of lyconadin C
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Total syntheses of lyconadins A-C.
Journal of the American Chemical Society, 2013Co-Authors: Takuya Nishimura, Aditya K. Unni, Satoshi Yokoshima, Tohru FukuyamaAbstract:The total synthesis of the Lycopodium alkaloid lyconadin A was accomplished and it was applied to the total syntheses of the related congeners, lyconadins B and C. Lyconadin A has attracted attention as a challenging target for total synthesis due to the unprecedented pentacyclic skeleton. Our synthesis of lyconadin A features a facile construction of the highly fused tetracyclic skeleton through a combination of an aza-Prins reaction and an electrocyclic ring opening, followed by formation of a C–N bond. Transformation of the Bromoalkene moiety of the tetracycle to a key enone intermediate was extensively investigated, and three methods via sulfide, oxime, or azide intermediates were established. A pyridone ring was constructed from the key enone intermediate to complete the synthesis of lyconadin A. A dihydropyridone ring could also be formed from the same enone intermediate, leading to a synthesis of lyconadin B. Establishment of the conditions for an electrocyclic ring opening without formation of the...
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Concise Total Synthesis of (+)-Lyconadin A
Journal of the American Chemical Society, 2010Co-Authors: Takuya Nishimura, Aditya K. Unni, Satoshi Yokoshima, Tohru FukuyamaAbstract:The total synthesis of lyconadin A from (R)-5-methylcyclohex-2-enone was accomplished. Our synthesis features the facile construction of a highly fused tetracyclic compound through a combination of an aza-Prins reaction and an electrocyclic ring opening. Transformation of the Bromoalkene moiety in the tetracycle could be achieved by either a vinylogous Pummerer rearrangement or the formation and subsequent isomerization of the nitrosoalkene to furnish an α,β-unsaturated ketone, from which the pyridone ring was constructed.
Takuya Nishimura - One of the best experts on this subject based on the ideXlab platform.
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Total Syntheses of Lyconadins A–C
2016Co-Authors: Takuya Nishimura, Satoshi Yokoshima, Aditya K. Unni, Tohru FukuyamaAbstract:The total synthesis of the Lycopodium alkaloid lyconadin A was accomplished and it was applied to the total syntheses of the related congeners, lyconadins B and C. Lyconadin A has attracted attention as a challenging target for total synthesis due to the unprecedented pentacyclic skeleton. Our synthesis of lyconadin A features a facile construction of the highly fused tetracyclic skeleton through a combination of an aza-Prins reaction and an electrocyclic ring opening, followed by formation of a C–N bond. Transformation of the Bromoalkene moiety of the tetracycle to a key enone intermediate was extensively investigated, and three methods via sulfide, oxime, or azide intermediates were established. A pyridone ring was constructed from the key enone intermediate to complete the synthesis of lyconadin A. A dihydropyridone ring could also be formed from the same enone intermediate, leading to a synthesis of lyconadin B. Establishment of the conditions for an electrocyclic ring opening without formation of the C–N bond resulted in completion of the total synthesis of lyconadin C
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Total syntheses of lyconadins A-C.
Journal of the American Chemical Society, 2013Co-Authors: Takuya Nishimura, Aditya K. Unni, Satoshi Yokoshima, Tohru FukuyamaAbstract:The total synthesis of the Lycopodium alkaloid lyconadin A was accomplished and it was applied to the total syntheses of the related congeners, lyconadins B and C. Lyconadin A has attracted attention as a challenging target for total synthesis due to the unprecedented pentacyclic skeleton. Our synthesis of lyconadin A features a facile construction of the highly fused tetracyclic skeleton through a combination of an aza-Prins reaction and an electrocyclic ring opening, followed by formation of a C–N bond. Transformation of the Bromoalkene moiety of the tetracycle to a key enone intermediate was extensively investigated, and three methods via sulfide, oxime, or azide intermediates were established. A pyridone ring was constructed from the key enone intermediate to complete the synthesis of lyconadin A. A dihydropyridone ring could also be formed from the same enone intermediate, leading to a synthesis of lyconadin B. Establishment of the conditions for an electrocyclic ring opening without formation of the...
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Concise Total Synthesis of (+)-Lyconadin A
Journal of the American Chemical Society, 2010Co-Authors: Takuya Nishimura, Aditya K. Unni, Satoshi Yokoshima, Tohru FukuyamaAbstract:The total synthesis of lyconadin A from (R)-5-methylcyclohex-2-enone was accomplished. Our synthesis features the facile construction of a highly fused tetracyclic compound through a combination of an aza-Prins reaction and an electrocyclic ring opening. Transformation of the Bromoalkene moiety in the tetracycle could be achieved by either a vinylogous Pummerer rearrangement or the formation and subsequent isomerization of the nitrosoalkene to furnish an α,β-unsaturated ketone, from which the pyridone ring was constructed.
Bernard Boutevin - One of the best experts on this subject based on the ideXlab platform.
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Radical Copolymerization of Vinylidene Fluoride with 8‐Bromo‐1H,1H,2H‐perfluorooct‐1‐ene: Microstructure, Crosslinking and Thermal Properties
Macromolecular Chemistry and Physics, 2007Co-Authors: L. Sauguet, Bruno Ameduri, Bernard BoutevinAbstract:An original synthesis of 8-bromo-1H,1H,2H-perfluorooct-1-ene (BDFO) and its radical copolymerization with vinylidene fluoride (VDF), initiated by 2,5-bis(tert-butylperoxy)-2, 5-dimethylhexane at 134°C, are presented. The fluorinated Bromoalkene was obtained by dehydrobromination of 1,8-dibromo-1H,1H,2H,2H-perfluorooctane in a satisfactory yield. Although BDFO did not homopolymerize under radical initiation, it did copolymerize with VDF. The compositions of the resulting random type copolymers were calculated by means of 19 F NMR spectroscopy and allowed the quantification of the respective amounts of both comonomers in the copolymers, showing good incorporation of the brominated monomer. Nevertheless, obtaining PVDF copolymers containing a high molar percentage of BDFO in good yields was difficult to achieve from initial molar ratios of BDFO higher than 9.2 mol-%. Radical terpolymerization of VDF, BDFO and hexafluoropropene (HFP) was also successfully achieved. BDFO contents in these co- or terpolymers ranged from 3.6 to 12.2 mol-%. The Bromoalkene acted as a cure site monomer and the resulting poly(VDF-co-BDFO) copolymers were crosslinked via the bromine atom in the presence of a triallyl isocyanurate/peroxide system. The materials obtained led to more thermally stable copolymers than the uncured ones and their thermostabilities were compared to those of commercially available poly(VDF-co-HFP) copolymers crosslinked using diamines.
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Radical Copolymerization of Vinylidene Fluoride with 8-Bromo-1H,1H,2Hperfluorooct- 1-ene: Microstructure, Crosslinking and Thermal Properties
Macromolecular Chemistry and Physics, 2007Co-Authors: Bruno Ameduri, L. Sauguet, Bernard BoutevinAbstract:An original synthesis of 8-bromo-1H,1H,2H-perfluorooct-1-ene (BDFO) and its radical copolymerization with vinylidene fluoride (VDF), initiated by 2,5-bis(tert-butylperoxy)-2, 5-dimethylhexane at 134 8C, are presented. The fluorinated Bromoalkene was obtained by dehydrobromination of 1,8-dibromo-1H,1H,2H,2H-perfluorooctane in a satisfactory yield. Although BDFO did not homopolymerize under radical initiation, it did copolymerize with VDF. The compositions of the resulting random type copolymers were calculated by means of 19F NMR spectroscopy and allowed the quantification of the respective amounts of both comonomers in the copolymers, showing good incorporation of the brominated monomer. Nevertheless, obtaining PVDF copolymers containing a high molar percentage of BDFO in good yields was difficult to achieve from initial molar ratios of BDFO higher than 9.2 mol-%. Radical terpolymerization of VDF, BDFO and hexafluoropropene (HFP) was also successfully achieved. BDFO contents in these co- or terpolymers ranged from 3.6 to 12.2 mol-%. The Bromoalkene acted as a cure site monomer and the resulting poly(VDF-co-BDFO) copolymers were crosslinked via the bromine atom in the presence of a triallyl isocyanurate/peroxide system. The materials obtained led to more thermally stable copolymers than the uncured ones and their thermostabilities were compared to those of commercially available poly(VDFco- HFP) copolymers crosslinked using diamines.
Hirokazu Urabe - One of the best experts on this subject based on the ideXlab platform.
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facile preparation of indoles and 1 2 benzothiazine 1 1 dioxides nucleophilic addition of sulfonamides to bromoacetylenes and subsequent palladium catalyzed cyclization
Angewandte Chemie, 2012Co-Authors: Masahito Yamagishi, Ken Nishigai, Azusa Ishii, Takeshi Hata, Hirokazu UrabeAbstract:Bromine as a double agent: The bromine atom in 1-bromo-1-alkynes works as an electron-withdrawing group to effect the nucleophilic addition of sulfonamides. It again plays a pivotal role in the palladium-catalyzed cyclization of the resultant (Z)-2-(sulfonylamino)-1-Bromoalkenes into nitrogen heterocycles (see scheme).
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Facile Preparation of Indoles and 1,2‐Benzothiazine 1,1‐Dioxides: Nucleophilic Addition of Sulfonamides to Bromoacetylenes and Subsequent Palladium‐Catalyzed Cyclization
Angewandte Chemie (International ed. in English), 2012Co-Authors: Masahito Yamagishi, Ken Nishigai, Azusa Ishii, Takeshi Hata, Hirokazu UrabeAbstract:Bromine as a double agent: The bromine atom in 1-bromo-1-alkynes works as an electron-withdrawing group to effect the nucleophilic addition of sulfonamides. It again plays a pivotal role in the palladium-catalyzed cyclization of the resultant (Z)-2-(sulfonylamino)-1-Bromoalkenes into nitrogen heterocycles (see scheme).
Dorota Gryko - One of the best experts on this subject based on the ideXlab platform.
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Vitamin B12-Catalyzed Dicarbofunctionalization of Bromoalkenes Under Visible Light Irradiation
Synthesis, 2020Co-Authors: Sabina Smoleń, Aleksandra Wincenciuk, Olga Drapała, Dorota GrykoAbstract:Vitamin B12 plays a crucial role in enzymatic transformations. This natural compound proved also useful as a catalyst in numerous organic reactions. Commercial availability and lower cost than precious metal complexes, make cobalamin an attractive candidate for a broader use as a benign Co-catalyst. Herein, the vitamin B12-catalyzed dicarbofuntionalization of Bromoalkenes with electrophilic olefins is reported leading to substituted pyrrolidines and piperidines in decent yields after only 15 minutes under light irradiation.
