The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Yujiro Hayashi - One of the best experts on this subject based on the ideXlab platform.
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amphiphilic immobilized diphenylprolinol alkyl Ether catalyst on ps peg resin
Bulletin of the Chemical Society of Japan, 2021Co-Authors: Seitaro Koshino, Shusuke Hattori, Shota Hasegawa, Naoki Haraguchi, Takeshi Yamamoto, Michinori Suginome, Yasuhiro Uozumi, Yujiro HayashiAbstract:Diphenylprolinol Silyl Ether is a widely used organocatalyst, and its immobilization on a solid support was investigated for the easy recycling and reuse of this catalyst. Because a Silyl Ether bon...
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asymmetric michael reaction of α cf3 thioester and α β unsaturated aldehyde catalyzed by diphenylprolinol Silyl Ether
Organic Letters, 2019Co-Authors: Yujiro Hayashi, Tomoaki Yamada, Misaki Sato, Shoya Watanabe, Eunsang Kwon, Kotaro Iwasaki, Shigenobu UmemiyaAbstract:Asymmetric Michael reaction of α-CF3 thioester and α,β-unsaturated aldehyde is catalyzed by diphenylprolinol Silyl Ether to afford the trifluoromethyl substituted Michael product with excellent enantioselectivity. Although the Michael products were generated as a mixture of syn- and anti-isomers, they can be transformed to single isomers of other useful compounds, such as lactone, lactam, piperidine, dihydropyran containing trifluoromethyl groups, or fluoro substituents.
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one pot synthesis of s baclofen via aldol condensation of acetaldehyde with diphenylprolinol Silyl Ether mediated asymmetric michael reaction as a key step
Organic Letters, 2016Co-Authors: Yujiro Hayashi, Daisuke Sakamoto, Daichi OkamuraAbstract:An efficient asymmetric total synthesis of (S)-baclofen was accomplished via a one-pot operation from commercially available materials using sequential reactions, such as aldol condensation of acetaldehyde, diphenylprolinol Silyl Ether mediated asymmetric Michael reaction of nitromethane, Kraus–Pinnick oxidation, and Raney Ni reduction. Highly enantioenriched baclofen was obtained in one pot with a good yield over four reactions.
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two reaction mechanisms via iminium ion intermediates the different reactivities of diphenylprolinol Silyl Ether and trifluoromethyl substituted diarylprolinol Silyl Ether
ChemInform, 2015Co-Authors: Hiroaki Gotoh, Tadafumi Uchimaru, Yujiro HayashiAbstract:The reaction of cinnamaldehyde with cyclopentadiene in the presence of DPPL as catalyst leads to substituted cyclopentadiene Michael-type adducts (III) and (IV), whilst the reaction with DTFP catalyst affords Diels—Alder adducts (V) and (VI).
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asymmetric aldol reaction of α α disubstituted acetaldehydes catalyzed by diphenylprolinol Silyl Ether for the construction of quaternary stereogenic centers
ChemInform, 2015Co-Authors: Yujiro Hayashi, Hiroki Shomura, Martin J Lear, Itaru SatoAbstract:The asymmetric cross-aldol reaction of α,α-disubstituted acetaldehydes with commercial ethyl glyoxylate polymer was successfully catalyzed by diphenylprolinol Silyl Ether 3 to generate all-carbon quaternary stereogenic centers with good enantioselectivity.
Jian Wang - One of the best experts on this subject based on the ideXlab platform.
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amine catalyzed enantioselective 1 3 dipolar cycloadditions of aldehydes to c n cyclic azomethine imines
ChemInform, 2014Co-Authors: Jian Wang, Wenjun Li, Zhiyun Du, Kun ZhangAbstract:The reactions between diversely substituted C,N-cyclic azomethine imines and aldehydes proceed smoothly in the presence of a chiral prolinol Silyl Ether catalyst, providing the C-1 substituted tetrahydroisoquinolines in a highly stereoselective fashion.
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amine catalyzed enantioselective 1 3 dipolar cycloadditions of aldehydes to c n cyclic azomethine imines
Chemistry: A European Journal, 2014Co-Authors: Jian Wang, Wenjun Li, Zhiyun Du, Kun ZhangAbstract:: Amine-catalyzed enantioselective 1,3-dipolar cycloadditions of aldehydes to C,N-cyclic azomethine imines were developed. The reactions between diversely substituted C,N-cyclic azomethine imines and aldehydes proceeded smoothly in the presence of chiral prolinol Silyl Ether catalyst and gave the C-1-substituted tetrahydroisoquinolines in a highly stereoselective manner. These tetrahydroisoquinolines could be efficiently transformed to several other useful polycyclic frameworks.
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highly enantioselective aldehyde nitroolefin michael addition reactions catalyzed by recyclable fluorous s diphenylpyrrolinol Silyl Ether
ChemInform, 2006Co-Authors: Jian Wang, Wei WangAbstract:A recyclable and reusable (S) diphenylpyrrolinol Silyl Ether I organocatalyst bearing a n-C8F17 fluorous tag has been demonstrated for promoting the asymmetric Michael addition reactions of a wide range of aldehydes with both aryl and alkyl-substituted nitroolefins and excellent levels of enantio- and diastereoselectivities are achieved. The catalyst I can be conveniently recovered by fluorous solid-phase extraction and subsequently reused (up to eight cycles) without significant loss of its catalytic activity and stereoselectivity for the process.
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enantioselective organocatalytic tandem michael aldol reactions one pot synthesis of chiral thiochromenes
Journal of the American Chemical Society, 2006Co-Authors: Wei Wang, Jian WangAbstract:A highly enantioselective (S) diphenylpyrrolinol Silyl Ether promoted tandem Michael−aldol reaction of α,β-unsaturated aldehydes with 2-mercaptobenzaldehydes has been developed. The method affords ...
Fumin Zhang - One of the best experts on this subject based on the ideXlab platform.
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efficient oxa diels alder semipinacol rearrangement aldol cascade reaction short approach to polycyclic architectures
ChemInform, 2015Co-Authors: Jinbao Peng, Yue Qi, Zeran Jing, Shaohua Wang, Yongqiang Tu, Fumin ZhangAbstract:A novel carbon electrophile induced intermolecular oxa-Diels—Alder/semipinacol rearrangement/aldol cascade reaction of allylic Silyl Ether with β,γ-unsaturated α-ketoester is developed under the promotion of SnCl4.
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efficient oxa diels alder semipinacol rearrangement aldol cascade reaction short approach to polycyclic architectures
Organic Letters, 2015Co-Authors: Jinbao Peng, Yue Qi, Zeran Jing, Shaohua Wang, Yongqiang Tu, Fumin ZhangAbstract:A novel carbon electrophile induced intermolecular oxa-Diels–Alder/semipinacol rearrangement/aldol cascade reaction of allylic Silyl Ether with β,γ-unsaturated α-ketoester has been developed under the promotion of SnCl4. This highly efficient transformation enables the quick construction of polycyclic architectures with up to five contiguous stereogenic centers in a single operation with moderate to good yields as well as high diastereoselectivity and would provide versatile short approaches to frameworks and/or analogues of numerous biologically important polycyclic natural products.
Hayato Ishikawa - One of the best experts on this subject based on the ideXlab platform.
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one pot synthesis of oseltamivir and mechanistic insights into the organocatalyzed michael reaction
Chemistry: A European Journal, 2013Co-Authors: Yujiro Hayashi, Hayato Ishikawa, Takasuke Mukaiyama, Hiroyuki KoshinoAbstract:The one-pot sequential synthesis of (−)-oseltamivir has been achieved without evaporation or solvent exchange in 36 % yield over seven reactions. The key step was the asymmetric Michael reaction of pentan-3-yloxyacetaldehyde with (Z)-N-2-nitroethenylacetamide, catalyzed by a diphenylprolinol Silyl Ether. The use of a bulky O-Silyl-substituted diphenylprolinol catalyst, chlorobenzene as a solvent, and HCO2H as an acid additive, were key to produce the first Michael adduct in both excellent yield and excellent diastereo- and enantioselectivity. Investigation into the effect of acid demonstrated that an acid additive accelerates not only the E–Z isomerization of the enamines derived from pentan-3-yloxyacetaldehyde with diphenylprolinol Silyl Ether, but also ring opening of the cyclobutane intermediate and the addition reaction of the enamine to (Z)-N-2-nitroethenylacetamide. The transition-state model for the Michael reaction of pentan-3-yloxyacetaldehyde with (Z)-N-2-nitroethenylacetamide was proposed by consideration of the absolute configuration of the major and minor isomers of the Michael product with the results of the Michael reaction of pentan-3-yloxyacetaldehyde with phenylmaleimide and naphthoquinone.
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organocatalyst mediated dehydrogenation of aldehydes to α β unsaturated aldehydes and oxidative and enantioselective reaction of aldehydes and nitromethane catalyzed by diphenylprolinol Silyl Ether
Advanced Synthesis & Catalysis, 2013Co-Authors: Yujiro Hayashi, Hayato Ishikawa, Takahiko ItohAbstract:A one-pot transformation of aldehydes into α,β-unsaturated aldehydes was developed using both N-benzyl-N-methylamine and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as catalysts and MnO2 as a terminal oxidant. An oxidative and enantioselective reaction of aldehydes and nitromethane was established using both diphenylprolinol Silyl Ether and DDQ as a catalyst with MnO2 as a terminal oxidant, in which synthetically important β-substituted γ-nitro aldehydes were obtained with excellent enantioselectivity.
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organocatalytic enantioselective intramolecular 6 2 cycloaddition reaction for the formation of tricyclopentanoids and insight on its mechanism from a computational study
Journal of the American Chemical Society, 2011Co-Authors: Yujiro Hayashi, Hiroaki Gotoh, Hayato Ishikawa, Seiji Tsuzuki, Masakazu Honma, Kuppusamy Sankar, Indresh Kumar, Kohzo Konno, Hiroharu Yui, Tadafumi UchimaruAbstract:Diphenylprolinol Silyl Ether was found to be an effective organocatalyst for promoting the asymmetric, catalytic, intramolecular [6 + 2] cycloaddition reactions of fulvenes substituted at the exocyclic 6-position with a δ-formylalkyl group to afford synthetically useful linear triquinane derivatives in good yields and excellent enantioselectivities. The cis-fused triquinane derivatives were obtained exclusively; the trans-fused isomers were not detected among the reaction products. The intramolecular [6 + 2] cycloaddition occurs between the fulvene functionality (6π) and the enamine double bond (2π) generated from the formyl group in the substrates and the diphenylprolinol Silyl Ether. The absolute configuration of the reaction products was determined by vibrational circular dichroism. The reaction mechanism was investigated using molecular orbital calculations, B3LYP and MP2 geometry optimizations, and subsequent single-point energy evaluations on model reaction sequences. These calculations revealed the...
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enantio and diastereoselective synthesis of piperidines by coupling of four components in a one pot sequence involving diphenylprolinol Silyl Ether mediated michael reaction
Organic Letters, 2010Co-Authors: Tatsuya Urushima, Daisuke Sakamoto, Hayato Ishikawa, Yujiro HayashiAbstract:An efficient, asymmetric, four-component, one-pot synthesis of highly substituted piperidines with excellent diastereo- and enantioselectivity was established through the diphenylprolinol Silyl Ether mediated Michael reaction of aldehyde and nitroalkene, followed by the domino aza-Henry reaction/hemiaminalization reaction and a Lewis acid mediated allylation or cyanation reaction. All carbons of the piperidine ring are substituted with different groups, and its five contiguous stereocenters are completely controlled in both relative and absolute senses.
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one pot synthesis of chiral bicyclo 3 3 0 octatrienes using diphenylprolinol Silyl Ether mediated ene type reaction
Tetrahedron, 2010Co-Authors: Hiroaki Gotoh, Hayato Ishikawa, Hiroshi Ogino, Yujiro HayashiAbstract:Chiral bicyclo[3.3.0]octatrienes with excellent enantioselectivity were synthesized from the simple starting materials of α,β-unsaturated aldehyde and cyclopentadiene via one-pot operation, which consisted of a diphenylprolinol Silyl Ether-mediated ene-type reaction, intramolecular addition reaction of cyclopentadiene moiety with aldehyde and dehydration reaction.
Tadafumi Uchimaru - One of the best experts on this subject based on the ideXlab platform.
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two reaction mechanisms via iminium ion intermediates the different reactivities of diphenylprolinol Silyl Ether and trifluoromethyl substituted diarylprolinol Silyl Ether
ChemInform, 2015Co-Authors: Hiroaki Gotoh, Tadafumi Uchimaru, Yujiro HayashiAbstract:The reaction of cinnamaldehyde with cyclopentadiene in the presence of DPPL as catalyst leads to substituted cyclopentadiene Michael-type adducts (III) and (IV), whilst the reaction with DTFP catalyst affords Diels—Alder adducts (V) and (VI).
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asymmetric nitrocyclopropanation of α substituted α β enals catalyzed by diphenylprolinol Silyl Ether for the construction of all carbon quaternary stereogenic centers
European Journal of Organic Chemistry, 2015Co-Authors: Yujiro Hayashi, Tatsuya Yamazaki, Yuki Nakanishi, Tsuyoshi Ono, Tohru Taniguchi, Kenji Monde, Tadafumi UchimaruAbstract:The diphenylprolinol Silyl Ether mediated asymmetric nitrocyclopropanation of α-substituted α,β-unsaturated aldehydes with bromonitromethane, followed by base-promoted isomerization was found to afford trans-nitrocyclopropanecarbaldehydes with all-carbon quaternary stereogenic centers with excellent diastereo- and enantioselectivities. DFT calculations indicated that the s-trans conformer of the iminium ion intermediate is more stable than the s-cis conformer. In addition, nucleophilic attack of the bromonitromethane anion to the iminium ion intermediate was calculated to occur preferentially from the opposite side of the bulky substituents of the pyrrolidine iminium intermediate.
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Two Reaction Mechanisms via Iminium Ion Intermediates: The Different Reactivities of Diphenylprolinol Silyl Ether and Trifluoromethyl-Substituted Diarylprolinol Silyl Ether.
Chemistry (Weinheim an der Bergstrasse Germany), 2015Co-Authors: Hiroaki Gotoh, Tadafumi Uchimaru, Yujiro HayashiAbstract:The reactions of α,β-unsaturated aldehydes with cyclopentadiene in the presence of diarylprolinol Silyl Ethers as catalyst proceed via iminium cations as intermediates, and can be divided into two types; one involving a Michael-type reaction (type A) and one involving a cycloaddition (type B). Diphenylprolinol Silyl Ethers and trifluoromethyl-substituted diarylprolinol Silyl Ethers, which are widely used proline-type organocatalysts, have been investigated in this study. As the LUMO of the iminium ion derived from trifluoromethyl-substituted diarylprolinol Silyl Ether is lower in energy than that derived from diphenylprolinol Silyl Ether, as supported by ab initio calculations, the trifluoromethyl-substituted catalyst is more reactive in a type B reaction. The iminium ion from an α,β-unsaturated aldehyde is generated more quickly with diphenylprolinol Silyl Ether than with the trifluoromethyl-substituted diarylprolinol Silyl Ether. When the generation of the iminium ion is the rate-determining step, the diphenylprolinol Silyl Ether catalyst is the more reactive. Because acid accelerates the generation of iminium ions and reduces the generation of anionic nucleophiles in the Michael-type reaction (type A), it is necessary to select the appropriate acid for specific reactions. In general, diphenylprolinol Silyl Ether is a superior catalyst for type A reactions, whereas the trifluoromethyl-substituted diarylprolinol Silyl Ether catalyst is preferred for type B reactions.
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a theoretical and experimental study of the effects of Silyl substituents in enantioselective reactions catalyzed by diphenylprolinol Silyl Ether
Chemistry: A European Journal, 2014Co-Authors: Hiroaki Gotoh, Tadafumi Uchimaru, Yujiro Hayashi, Daichi Okamura, Tatsuya Yamazaki, Yasuto Ameda, Seiji Tsuzuki, Dieter SeebachAbstract:The effect of Silyl substituents in diphenylprolinol Silyl Ether catalysts was investigated. Mechanistically, reactions catalyzed by diphenylprolinol Silyl Ether can be categorized into three types: two that involve an iminium ion intermediate, such as for the Michael-type reaction (type A) and the cycloaddition reaction (type B), and one that proceeds via an enamine intermediate (type C). In the Michael-type reaction via iminium ions (type A), excellent enantioselectivity is realized when the catalyst with a bulky Silyl moiety is employed, in which efficient shielding of a diastereotopic face of the iminium ion is directed by the bulky Silyl moiety. In the cycloaddition reaction of iminium ions (type B) and reactions via enamines (type C), excellent enantioselectivity is obtained even when the Silyl group is less bulky and, in this case, too much bulk reduces the reaction rate. In other cases, the yield increases when diphenylprolinol Silyl Ethers with bulky substituents are employed, presumably by suppressing side reactions between the nucleophilic catalyst and the reagent. The conformational behaviors of the iminium and enamine species have been determined by theoretical calculations. These data explain the effect of the bulkiness of the Silyl substituent on the enantioselectivity and reactivity of the catalysts.
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organocatalytic enantioselective intramolecular 6 2 cycloaddition reaction for the formation of tricyclopentanoids and insight on its mechanism from a computational study
Journal of the American Chemical Society, 2011Co-Authors: Yujiro Hayashi, Hiroaki Gotoh, Hayato Ishikawa, Seiji Tsuzuki, Masakazu Honma, Kuppusamy Sankar, Indresh Kumar, Kohzo Konno, Hiroharu Yui, Tadafumi UchimaruAbstract:Diphenylprolinol Silyl Ether was found to be an effective organocatalyst for promoting the asymmetric, catalytic, intramolecular [6 + 2] cycloaddition reactions of fulvenes substituted at the exocyclic 6-position with a δ-formylalkyl group to afford synthetically useful linear triquinane derivatives in good yields and excellent enantioselectivities. The cis-fused triquinane derivatives were obtained exclusively; the trans-fused isomers were not detected among the reaction products. The intramolecular [6 + 2] cycloaddition occurs between the fulvene functionality (6π) and the enamine double bond (2π) generated from the formyl group in the substrates and the diphenylprolinol Silyl Ether. The absolute configuration of the reaction products was determined by vibrational circular dichroism. The reaction mechanism was investigated using molecular orbital calculations, B3LYP and MP2 geometry optimizations, and subsequent single-point energy evaluations on model reaction sequences. These calculations revealed the...