The Experts below are selected from a list of 147 Experts worldwide ranked by ideXlab platform
Yoo Tanabe - One of the best experts on this subject based on the ideXlab platform.
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Asymmetric Total Syntheses of Two 3-Acyl-5,6- dihydro-2H-pyrones: (R)-Podoblastin-S and (R)- Lachnelluloic Acid with Verification of the Absolute Configuration of (−)-Lachnelluloic Acid
Molecules (Basel Switzerland), 2017Co-Authors: Tetsuya Fujiwara, Takeshi Tsutsumi, Kohei Nakata, Hidefumi Nakatsuji, Yoo TanabeAbstract:Expedient asymmetric total syntheses of both (R)-podoblastin-S and (R)-lachnelluloic acid, representative of natural 3-acyl-5,6-dihydro-2H-pyran-2-ones, were performed. Compared with the reported total synthesis of (R)-podoblastin-S (14 steps, overall 5% yield), the present study was achieved in only five steps in an overall 40% yield and with 98% ee (HPLC analysis). In a similar strategy, the first asymmetric total synthesis of the relevant (R)-lachnelluloic acid was achieved in an overall 40% yield with 98% ee (HPLC analysis). The crucial step utilized readily accessible and reliable Soriente and Scettri’s Ti(OiPr)4/(S)-BINOL‒catalyzed asymmetric Mukaiyama Aldol Addition of 1,3-bis(trimethylsiloxy)diene, derived from ethyl acetoacetate with n-butanal for (R)- podoblastin-S and n-pentanal for (R)-lachnelluloic acid. With the comparison of the specific rotation values between the natural product and the synthetic specimen, the hitherto unknown absolute configuration at the C(6) position of (−)-lachnelluloic acid was unambiguously elucidated as 6R.
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catalytic tmscl promoted powerful Aldol Addition and claisen condensation mediated by ticl4 bu3n agent comparison and evaluation with the Mukaiyama Aldol Addition
Tetrahedron Letters, 1999Co-Authors: Yoshihiro Yoshida, Noriaki Matsumoto, Ryota Hamasaki, Yoo TanabeAbstract:Abstract MSCl catalyst (0.05 equiv) signifiantly promoted the TiCl 4 /Bu 3 N-mediated direct cross Aldol Additions of sterically crowded ketones and α-hetero substituted ketones, and also the direct Claisen condensation between methyl esters.
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Catalytic TMSCl promoted powerful Aldol Addition and Claisen condensation mediated by TiCl4/Bu3N agent: comparison and evaluation with the Mukaiyama Aldol Addition
Tetrahedron Letters, 1999Co-Authors: Yoshihiro Yoshida, Noriaki Matsumoto, Ryota Hamasaki, Yoo TanabeAbstract:Abstract MSCl catalyst (0.05 equiv) signifiantly promoted the TiCl 4 /Bu 3 N-mediated direct cross Aldol Additions of sterically crowded ketones and α-hetero substituted ketones, and also the direct Claisen condensation between methyl esters.
Grant J. Dixon - One of the best experts on this subject based on the ideXlab platform.
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One-pot enol silane formation-Mukaiyama Aldol reactions: Crossed aldehyde-aldehyde coupling, thioester substrates, and reactions in ester solvents
Tetrahedron Letters, 2019Co-Authors: C. Wade Downey, Anna Takashima, Grant J. Dixon, Jared A. Ingersoll, Claire N. Fuller, Kenneth W. Maccormac, Rohina SediquiAbstract:Abstract Trimethylsilyl trifluoromethanesulfonate (TMSOTf) and a trialkylamine base promote both in situ enol silane/silyl ketene acetal formation and Mukaiyama Aldol Addition reactions between a variety of reaction partners in a single reaction flask. Isolation of the required enol silane or silyl ketene acetal is not necessary. For example, crossed Aldol reactions between α-disubstituted aldehydes and non-enolizable aldehydes yield β-hydroxy aldehydes in good yield. In a related reaction, the common laboratory solvent ethyl acetate functions as both an enolate precursor and a green reaction solvent. When thioesters are employed as enolate precursors, high yields for Additions to non-enolizable aldehydes are routinely observed.
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Chalcone and cinnamate synthesis via one-pot enol silane formation-Mukaiyama Aldol reactions of ketones and acetate esters
Tetrahedron Letters, 2018Co-Authors: C. Wade Downey, Hadleigh M. Glist, Anna Takashima, Samuel R. Bottum, Grant J. DixonAbstract:Abstract Aryl alkyl ketones, acetate esters, and acetamides undergo facile one-pot enol silane formation, Mukaiyama Aldol Addition, and dehydrosilyloxylation in the presence of an amine base and excess trimethylsilyl trifluoromethanesulfonate. The chalcone and cinnamate products are generally recovered in high yield. The relative stoichiometry of the trimethylsilyl trifluoromethanesulfonate and amine base reagents determines whether the reaction yields the β-silyloxy carbonyl product or the α,β-unsaturated carbonyl.
Yoshihiro Yoshida - One of the best experts on this subject based on the ideXlab platform.
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catalytic tmscl promoted powerful Aldol Addition and claisen condensation mediated by ticl4 bu3n agent comparison and evaluation with the Mukaiyama Aldol Addition
Tetrahedron Letters, 1999Co-Authors: Yoshihiro Yoshida, Noriaki Matsumoto, Ryota Hamasaki, Yoo TanabeAbstract:Abstract MSCl catalyst (0.05 equiv) signifiantly promoted the TiCl 4 /Bu 3 N-mediated direct cross Aldol Additions of sterically crowded ketones and α-hetero substituted ketones, and also the direct Claisen condensation between methyl esters.
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Catalytic TMSCl promoted powerful Aldol Addition and Claisen condensation mediated by TiCl4/Bu3N agent: comparison and evaluation with the Mukaiyama Aldol Addition
Tetrahedron Letters, 1999Co-Authors: Yoshihiro Yoshida, Noriaki Matsumoto, Ryota Hamasaki, Yoo TanabeAbstract:Abstract MSCl catalyst (0.05 equiv) signifiantly promoted the TiCl 4 /Bu 3 N-mediated direct cross Aldol Additions of sterically crowded ketones and α-hetero substituted ketones, and also the direct Claisen condensation between methyl esters.
C. Wade Downey - One of the best experts on this subject based on the ideXlab platform.
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One-pot enol silane formation-Mukaiyama Aldol reactions: Crossed aldehyde-aldehyde coupling, thioester substrates, and reactions in ester solvents
Tetrahedron Letters, 2019Co-Authors: C. Wade Downey, Anna Takashima, Grant J. Dixon, Jared A. Ingersoll, Claire N. Fuller, Kenneth W. Maccormac, Rohina SediquiAbstract:Abstract Trimethylsilyl trifluoromethanesulfonate (TMSOTf) and a trialkylamine base promote both in situ enol silane/silyl ketene acetal formation and Mukaiyama Aldol Addition reactions between a variety of reaction partners in a single reaction flask. Isolation of the required enol silane or silyl ketene acetal is not necessary. For example, crossed Aldol reactions between α-disubstituted aldehydes and non-enolizable aldehydes yield β-hydroxy aldehydes in good yield. In a related reaction, the common laboratory solvent ethyl acetate functions as both an enolate precursor and a green reaction solvent. When thioesters are employed as enolate precursors, high yields for Additions to non-enolizable aldehydes are routinely observed.
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Chalcone and cinnamate synthesis via one-pot enol silane formation-Mukaiyama Aldol reactions of ketones and acetate esters
Tetrahedron Letters, 2018Co-Authors: C. Wade Downey, Hadleigh M. Glist, Anna Takashima, Samuel R. Bottum, Grant J. DixonAbstract:Abstract Aryl alkyl ketones, acetate esters, and acetamides undergo facile one-pot enol silane formation, Mukaiyama Aldol Addition, and dehydrosilyloxylation in the presence of an amine base and excess trimethylsilyl trifluoromethanesulfonate. The chalcone and cinnamate products are generally recovered in high yield. The relative stoichiometry of the trimethylsilyl trifluoromethanesulfonate and amine base reagents determines whether the reaction yields the β-silyloxy carbonyl product or the α,β-unsaturated carbonyl.
Roger Hunter - One of the best experts on this subject based on the ideXlab platform.
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4 5 erythro 5 6 threo stereoselectivity in vinylogous Mukaiyama Aldol Addition of a silyloxypyrrole to a threose derivative stereochemical rationalization and relevance to castanospermine synthesis
Tetrahedron Letters, 2007Co-Authors: Roger Hunter, Sophie C M ReesjonesAbstract:Vinylogous Mukaiyama Aldol Addition of N - p -methoxybenzyl-4-methoxy-2-trimethylsilyloxypyrrole 7 to bis-MOM threose 6 using SnCl 4 as promoter gave the 4,5- erythro /5,6- threo adduct 8 , with the correct absolute configurations for the castanospermine framework as determined by a single-crystal X-ray structure. A transition-state model is presented to rationalize the stereoselectivity.
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4,5- erythro /5,6- threo -Stereoselectivity in vinylogous Mukaiyama Aldol Addition of a silyloxypyrrole to a threose derivative: stereochemical rationalization and relevance to (+)-castanospermine synthesis
Tetrahedron Letters, 2007Co-Authors: Roger Hunter, Sophie C. M. Rees-jonesAbstract:Vinylogous Mukaiyama Aldol Addition of N - p -methoxybenzyl-4-methoxy-2-trimethylsilyloxypyrrole 7 to bis-MOM threose 6 using SnCl 4 as promoter gave the 4,5- erythro /5,6- threo adduct 8 , with the correct absolute configurations for the castanospermine framework as determined by a single-crystal X-ray structure. A transition-state model is presented to rationalize the stereoselectivity.