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Naoya Kumagai - One of the best experts on this subject based on the ideXlab platform.
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direct catalytic asymmetric aldol reaction of thioamide with an α vinyl appendage
Chemistry: A European Journal, 2018Co-Authors: Jin Cui, Akimichi Ohtsuki, Takumi Watanabe, Naoya KumagaiAbstract:The direct catalytic asymmetric aldol reaction is an emerging catalytic methodology that provides atom-economical access to functionalized chiral building blocks. Thioamides are useful aldol donors due to their high-fidelity chemoselective enolization and divergent post-aldol transformations. Herein we describe the incorporation of an α-vinyl appendage on a thioamide, which expands the utility of aldol adducts for natural product synthesis. This vinylated thioamide was not accommodated under the previously identified catalyst settings, but the newly developed catalytic conditions furnished aldol products containing the pendant vinyl group.
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Direct Catalytic Asymmetric Conjugate Addition of Saturated and Unsaturated Thioamides.
ChemInform, 2015Co-Authors: Nilanjana Majumdar, Akira Saito, Liang Yin, Naoya KumagaiAbstract:It is found that the thioamide moiety is crucial to promote both the efficient enolization of thiolactam pronucleophiles and the subsequent stereoselective conjugate addition to α,β-unsaturated Thioamides.
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Direct Catalytic Asymmetric Conjugate Addition of Saturated and Unsaturated Thioamides
Organic Letters, 2015Co-Authors: Nilanjana Majumdar, Akira Saito, Liang Yin, Naoya KumagaiAbstract:Direct catalytic asymmetric conjugate addition of thiolactams to α,β-unsaturated Thioamides was efficiently promoted by a soft Lewis acid/hard Bronsted base cooperative catalyst in a highly stereocontrolled manner. Thioamide functionality was crucial to promote both the efficient enolization of thiolactam pronucleophiles and the subsequent stereoselective conjugate addition to α,β-unsaturated Thioamides. Differential manipulation of the two thioamide functionalities of the product highlights the synthetic utility of the present catalytic system.
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intermediate as catalyst catalytic asymmetric conjugate addition of nitroalkanes to α β unsaturated Thioamides
Organic Letters, 2012Co-Authors: Takanori Ogawa, Ryo Yazaki, Naoya Kumagai, Shinsuke Mouri, Masakatsu ShibasakiAbstract:Catalytic asymmetric conjugate addition of nitroalkanes to α,β-unsaturated Thioamides is promoted by a mesitylcopper/(R)-DTBM-Segphos precatalyst, affording γ-nitroThioamides in moderate to high syn-selectivity and excellent enantioselectivity. The intermediate Cu-thioamide enolate functions as a soft Lewis acid/hard Bronsted base cooperative catalyst to drive the catalytic cycle efficiently under proton transfer conditions.
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cooperative activation of alkyne and thioamide functionalities direct catalytic asymmetric conjugate addition of terminal alkynes to α β unsaturated Thioamides
ChemInform, 2011Co-Authors: Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:Key feature of the title conjugate addition reaction is the cooperative activation of both the alkyne and the thioamide by a combined soft Lewis acid—hard Broensted base catalyst system.
Masakatsu Shibasaki - One of the best experts on this subject based on the ideXlab platform.
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intermediate as catalyst catalytic asymmetric conjugate addition of nitroalkanes to α β unsaturated Thioamides
Organic Letters, 2012Co-Authors: Takanori Ogawa, Ryo Yazaki, Naoya Kumagai, Shinsuke Mouri, Masakatsu ShibasakiAbstract:Catalytic asymmetric conjugate addition of nitroalkanes to α,β-unsaturated Thioamides is promoted by a mesitylcopper/(R)-DTBM-Segphos precatalyst, affording γ-nitroThioamides in moderate to high syn-selectivity and excellent enantioselectivity. The intermediate Cu-thioamide enolate functions as a soft Lewis acid/hard Bronsted base cooperative catalyst to drive the catalytic cycle efficiently under proton transfer conditions.
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cooperative activation of alkyne and thioamide functionalities direct catalytic asymmetric conjugate addition of terminal alkynes to α β unsaturated Thioamides
ChemInform, 2011Co-Authors: Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:Key feature of the title conjugate addition reaction is the cooperative activation of both the alkyne and the thioamide by a combined soft Lewis acid—hard Broensted base catalyst system.
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a simplified catalytic system for direct catalytic asymmetric aldol reaction of Thioamides application to an enantioselective synthesis of atorvastatin
Tetrahedron, 2011Co-Authors: Yuji Kawato, Ryo Yazaki, Naoya Kumagai, Mitsutaka Iwata, Masakatsu ShibasakiAbstract:Abstract A new catalytic system was developed for the direct catalytic asymmetric aldol reaction of Thioamides. The new lithium-free Cu catalyst (second-generation catalyst) exhibited enhanced catalytic efficiency over the previously developed catalyst comprising [Cu(CH 3 CN) 4 ]PF 6 /Ph-BPE/LiOAr (first-generation catalyst), which required a tedious catalyst preparation process. In the reaction with the second-generation catalyst, the intermediate Cu-aldolate functioned as a Bronsted base to generate thioamide enolate, efficiently driving the catalytic cycle. The present aldol methodology culminated in a concise asymmetric synthesis of atorvastatin (Lipitor ® : atorvastatin calcium), a widely prescribed HMG-CoA reductase inhibitor for lowering low-density lipoprotein cholesterol.
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cooperative activation of alkyne and thioamide functionalities direct catalytic asymmetric conjugate addition of terminal alkynes to α β unsaturated Thioamides
Chemistry-an Asian Journal, 2011Co-Authors: Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:A detailed study of the direct catalytic asymmetric conjugate addition of terminal alkynes to α,β-unsaturated Thioamides is described. A soft Lewis acid/hard Bronsted base cooperative catalyst, comprising [Cu(CH(3)CN)(4)]PF(6), bisphosphine ligand, and Li(OC(6)H(4)-p-OMe) simultaneously activated both substrates to compensate for the low reactivity of copper alkynylide. A series of control experiments revealed that the intermediate copper-thioamide enolate functioned as a Bronsted base to generate copper alkynylide from the terminal alkyne, thus driving the catalytic cycle through an efficient proton transfer between substrates. These findings led to the identification of a more convenient catalyst using potassium hexamethyldisilazane (KHMDS) as the Bronsted base, which was particularly effective for the reaction of silylacetylenes. Divergent transformation of the thioamide functionality and a concise enantioselective synthesis of a GPR40 receptor agonist AMG-837 highlighted the synthetic utility of the present catalysis.
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direct catalytic enantio and diastereoselective aldol reaction of Thioamides
Journal of the American Chemical Society, 2011Co-Authors: Mitsutaka Iwata, Naoya Kumagai, Ryo Yazaki, Ihon Chen, Devarajulu Sureshkumar, Masakatsu ShibasakiAbstract:A direct catalytic asymmetric aldol reaction of Thioamides using a soft Lewis acid/hard Bronsted base cooperative catalyst comprising (R,R)-Ph-BPE/[Cu(CH3CN)4]PF6/LiOAr is described. Exclusive enolate generation from thioacetamides through a soft−soft interaction with the soft Lewis acid allowed for a direct aldol reaction to α-nonbranched aliphatic aldehydes, which are usually susceptible to self-condensation under conventional basic conditions. A hard Lewis basic phosphine oxide has emerged as an effective additive to constitute a highly active ternary soft Lewis acid/hard Bronsted base/hard Lewis base cooperative catalyst, enabling a direct enantio- and diastereoselective aldol reaction of thiopropionamides. Strict control of the amount of the hard Lewis base was essential to drive the catalytic cycle efficiently with a minimized retro-aldol pathway, affording syn-aldol products with high stereoselectivity. Divergent transformation of the thioamide functionality is an obvious merit of the present aldol...
Toshiaki Murai - One of the best experts on this subject based on the ideXlab platform.
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direct c h bond arylation of thienyl Thioamides catalyzed by pd phenanthroline complexes
Organic Letters, 2015Co-Authors: Takayuki Yamauchi, Fumitoshi Shibahara, Toshiaki MuraiAbstract:A direct C–H bond arylation method for thienyl Thioamides catalyzed by [Pd(phen)2](PF6)2 was developed. This reaction selectively afforded 2-monoarylated products, while the corresponding amide thiophene derivatives furnished 2,5-diarylated products. Mechanistic studies revealed that a Pd(II)–bisthioamide complex should be the active species for the reaction of thienyl Thioamides in the presence of catalytic amounts of [Pd(phen)2](PF6)2. Similar to the reaction with amides, the reaction with Thioamides selectively generated the 2,5-diarylated products when a preformed Pd(phen)PhI complex was used.
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intramolecular cyclization of in situ generated adducts formed between thioamide dianions and thioformamides leading to generation of 5 amino 2 thiazolines and 5 aminothiazoles and their fluorescence properties
Organic Letters, 2011Co-Authors: Toshiaki Murai, Fumihiko Hori, Toshifumi MaruyamaAbstract:Reactions of thioamide dianions, derived from secondary N-arylmethyl Thioamides using BuLi, with thioformamides followed by the addition of iodine to yield 5-amino-2-thiazolines are described. Treatment of the 5-amino-2-thiazolines with iodine leads to a highly efficient production of 5-aminothiazoles. When N,N-diarylthioformamides are employed in this process, fluorescent 5-N,N-diarylthiazoles are obtained.
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thioamide dianions derived from n arylmethyl Thioamides generation and application as carbon nucleophiles adjacent to the nitrogen atom
Pure and Applied Chemistry, 2010Co-Authors: Toshiaki MuraiAbstract:This review illustrates the ready availability of thioamide dianions and their versa- tility as carbon nucleophiles adjacent to the nitrogen atom. The products derived from the ad- dition of thioamide dianions to a range of electrophiles can participate in a cyclization reac- tion to form nitrogen-containing heterocycles. The electronic properties of thioamide dianions are also considered.
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n thioacyl 1 3 amino alcohols synthesis via ring opening of oxiranes with thioamide dianions and applications as key intermediates leading to stereochemically defined 5 6 dihydro 4h 1 3 oxazines and 1 3 amino alcohols
Journal of Organic Chemistry, 2005Co-Authors: Toshiaki Murai, Hideo Aso, Hiroaki Sano, Hiroyasu Kawai, Fumitoshi ShibaharaAbstract:N-Thioacyl 1,3-amino alcohols were synthesized via the ring-opening of oxiranes with thioamide dianions generated from N-benzyl Thioamides and BuLi in a highly regio- and stereoselective manner. The diastereomers of N-thioacyl 1,3-amino alcohols were readily separated by column chromatography to give stereochemically defined N-thioacyl 1,3-amino alcohols. They underwent intramolecular cyclization with Bu4F and EtI to give 5,6-dihydro-4H-1,3-oxazines. The reaction was specific with anti-N-thioacyl 1,3-amino alcohols, and cis-5,6-dihydro-4H-1,3-oxazines were obtained with high efficiency, whereas the reaction of a syn-alcohol gave a thioimidate as a major product. The reduction of N-thioacyl 1,3-amino alcohols with LiAlH4gave N-alkyl 1,3-amino alcohols in high yields. The use of optically active propylene oxide as a starting material gave the corresponding oxazine and alcohols in optically pure forms.
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iodo cyclization of n homoallyl Thioamides leading to 2 4 diaryl 5 6 dihydro 4h 1 3 thiazines
Chemistry Letters, 2004Co-Authors: Toshiaki Murai, Hisayuki Niwa, Tsutomu Kimura, Fumitoshi ShibaharaAbstract:Iodo-cyclization of N-homoallyl Thioamides was carried out in the presence of Et3N to form 2,4-diaryl-5,6-dihydro-4H-1,3-thiazines in good to high yields. The reaction of Thioamides bearing 1-napht...
Ryo Yazaki - One of the best experts on this subject based on the ideXlab platform.
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intermediate as catalyst catalytic asymmetric conjugate addition of nitroalkanes to α β unsaturated Thioamides
Organic Letters, 2012Co-Authors: Takanori Ogawa, Ryo Yazaki, Naoya Kumagai, Shinsuke Mouri, Masakatsu ShibasakiAbstract:Catalytic asymmetric conjugate addition of nitroalkanes to α,β-unsaturated Thioamides is promoted by a mesitylcopper/(R)-DTBM-Segphos precatalyst, affording γ-nitroThioamides in moderate to high syn-selectivity and excellent enantioselectivity. The intermediate Cu-thioamide enolate functions as a soft Lewis acid/hard Bronsted base cooperative catalyst to drive the catalytic cycle efficiently under proton transfer conditions.
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cooperative activation of alkyne and thioamide functionalities direct catalytic asymmetric conjugate addition of terminal alkynes to α β unsaturated Thioamides
ChemInform, 2011Co-Authors: Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:Key feature of the title conjugate addition reaction is the cooperative activation of both the alkyne and the thioamide by a combined soft Lewis acid—hard Broensted base catalyst system.
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a simplified catalytic system for direct catalytic asymmetric aldol reaction of Thioamides application to an enantioselective synthesis of atorvastatin
Tetrahedron, 2011Co-Authors: Yuji Kawato, Ryo Yazaki, Naoya Kumagai, Mitsutaka Iwata, Masakatsu ShibasakiAbstract:Abstract A new catalytic system was developed for the direct catalytic asymmetric aldol reaction of Thioamides. The new lithium-free Cu catalyst (second-generation catalyst) exhibited enhanced catalytic efficiency over the previously developed catalyst comprising [Cu(CH 3 CN) 4 ]PF 6 /Ph-BPE/LiOAr (first-generation catalyst), which required a tedious catalyst preparation process. In the reaction with the second-generation catalyst, the intermediate Cu-aldolate functioned as a Bronsted base to generate thioamide enolate, efficiently driving the catalytic cycle. The present aldol methodology culminated in a concise asymmetric synthesis of atorvastatin (Lipitor ® : atorvastatin calcium), a widely prescribed HMG-CoA reductase inhibitor for lowering low-density lipoprotein cholesterol.
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cooperative activation of alkyne and thioamide functionalities direct catalytic asymmetric conjugate addition of terminal alkynes to α β unsaturated Thioamides
Chemistry-an Asian Journal, 2011Co-Authors: Ryo Yazaki, Naoya Kumagai, Masakatsu ShibasakiAbstract:A detailed study of the direct catalytic asymmetric conjugate addition of terminal alkynes to α,β-unsaturated Thioamides is described. A soft Lewis acid/hard Bronsted base cooperative catalyst, comprising [Cu(CH(3)CN)(4)]PF(6), bisphosphine ligand, and Li(OC(6)H(4)-p-OMe) simultaneously activated both substrates to compensate for the low reactivity of copper alkynylide. A series of control experiments revealed that the intermediate copper-thioamide enolate functioned as a Bronsted base to generate copper alkynylide from the terminal alkyne, thus driving the catalytic cycle through an efficient proton transfer between substrates. These findings led to the identification of a more convenient catalyst using potassium hexamethyldisilazane (KHMDS) as the Bronsted base, which was particularly effective for the reaction of silylacetylenes. Divergent transformation of the thioamide functionality and a concise enantioselective synthesis of a GPR40 receptor agonist AMG-837 highlighted the synthetic utility of the present catalysis.
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direct catalytic enantio and diastereoselective aldol reaction of Thioamides
Journal of the American Chemical Society, 2011Co-Authors: Mitsutaka Iwata, Naoya Kumagai, Ryo Yazaki, Ihon Chen, Devarajulu Sureshkumar, Masakatsu ShibasakiAbstract:A direct catalytic asymmetric aldol reaction of Thioamides using a soft Lewis acid/hard Bronsted base cooperative catalyst comprising (R,R)-Ph-BPE/[Cu(CH3CN)4]PF6/LiOAr is described. Exclusive enolate generation from thioacetamides through a soft−soft interaction with the soft Lewis acid allowed for a direct aldol reaction to α-nonbranched aliphatic aldehydes, which are usually susceptible to self-condensation under conventional basic conditions. A hard Lewis basic phosphine oxide has emerged as an effective additive to constitute a highly active ternary soft Lewis acid/hard Bronsted base/hard Lewis base cooperative catalyst, enabling a direct enantio- and diastereoselective aldol reaction of thiopropionamides. Strict control of the amount of the hard Lewis base was essential to drive the catalytic cycle efficiently with a minimized retro-aldol pathway, affording syn-aldol products with high stereoselectivity. Divergent transformation of the thioamide functionality is an obvious merit of the present aldol...
Fumitoshi Shibahara - One of the best experts on this subject based on the ideXlab platform.
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direct c h bond arylation of thienyl Thioamides catalyzed by pd phenanthroline complexes
Organic Letters, 2015Co-Authors: Takayuki Yamauchi, Fumitoshi Shibahara, Toshiaki MuraiAbstract:A direct C–H bond arylation method for thienyl Thioamides catalyzed by [Pd(phen)2](PF6)2 was developed. This reaction selectively afforded 2-monoarylated products, while the corresponding amide thiophene derivatives furnished 2,5-diarylated products. Mechanistic studies revealed that a Pd(II)–bisthioamide complex should be the active species for the reaction of thienyl Thioamides in the presence of catalytic amounts of [Pd(phen)2](PF6)2. Similar to the reaction with amides, the reaction with Thioamides selectively generated the 2,5-diarylated products when a preformed Pd(phen)PhI complex was used.
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n thioacyl 1 3 amino alcohols synthesis via ring opening of oxiranes with thioamide dianions and applications as key intermediates leading to stereochemically defined 5 6 dihydro 4h 1 3 oxazines and 1 3 amino alcohols
Journal of Organic Chemistry, 2005Co-Authors: Toshiaki Murai, Hideo Aso, Hiroaki Sano, Hiroyasu Kawai, Fumitoshi ShibaharaAbstract:N-Thioacyl 1,3-amino alcohols were synthesized via the ring-opening of oxiranes with thioamide dianions generated from N-benzyl Thioamides and BuLi in a highly regio- and stereoselective manner. The diastereomers of N-thioacyl 1,3-amino alcohols were readily separated by column chromatography to give stereochemically defined N-thioacyl 1,3-amino alcohols. They underwent intramolecular cyclization with Bu4F and EtI to give 5,6-dihydro-4H-1,3-oxazines. The reaction was specific with anti-N-thioacyl 1,3-amino alcohols, and cis-5,6-dihydro-4H-1,3-oxazines were obtained with high efficiency, whereas the reaction of a syn-alcohol gave a thioimidate as a major product. The reduction of N-thioacyl 1,3-amino alcohols with LiAlH4gave N-alkyl 1,3-amino alcohols in high yields. The use of optically active propylene oxide as a starting material gave the corresponding oxazine and alcohols in optically pure forms.
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iodo cyclization of n homoallyl Thioamides leading to 2 4 diaryl 5 6 dihydro 4h 1 3 thiazines
Chemistry Letters, 2004Co-Authors: Toshiaki Murai, Hisayuki Niwa, Tsutomu Kimura, Fumitoshi ShibaharaAbstract:Iodo-cyclization of N-homoallyl Thioamides was carried out in the presence of Et3N to form 2,4-diaryl-5,6-dihydro-4H-1,3-thiazines in good to high yields. The reaction of Thioamides bearing 1-napht...
