Katsumi Nishimura

The conjugate addition-aldol tandem reaction of α,β-unsaturated esters catalyzed by lithium benzenethiolate

Abstract Reactions of α,β-unsaturated esters with aldehydes were catalyzed by 0.2 equiv of lithium benzenethiolate in the presence of phenyl trimethylsilyl sulfide to afford the conjugate addition-aldol tandem reaction products in the anti stereoselectivity and good to high yields.

Total synthesis of (-)-lycorine and (-)-2-epi-lycorine by asymmetric conjugate addition cascade.

Total syntheses of (-)-lycorine and (-)-2-epi-lycorine were accomplished using chiral ligand-controlled asymmetric cascade conjugate addition methodology, which enables the formation of two C-C bonds and three stereogenic centers in one pot to give synthetically useful chiral cyclohexane derivatives.

Catalytic Enantioselective Protonation of Lithium Ester Enolates Generated by Conjugate Addition of Arylthiolate to Enoates

A chiral ligand, a catalytic amount of lithium cation, and no chiral proton source: These are features of the present asymmetric addition-protonation of propenoates with 2-trimethylsilylbenzenethiol. The reaction is catalyzed by a combination of lithium 2-trimethylsilylbenzenethiolate and the chiral ligand 1. Desulfurization of the product affords 2-substituted propanoates with high ee values and without racemization. Furthermore, 1 can be recovered quantitatively for reuse.

Efficient cyclization of ω-oxo-α,β-unsaturated esters using lithium thiolate-initiated Michael-aldol tandem reaction

Abstract The reaction of ω-oxo-α,β-unsaturated esters with lithium thiolates afforded the Michael-aldol tandem cyclization products in good to perfect stereoselectivity depending on the nature of thiolates.

Structural requirements of a chiral ligand for the catalytic asymmetric addition of thiophenol to α,β-unsaturated esters

The tridentate amino ether ligands 1 and 14 were developed through systematic structural modification of the bidentate diether ligand 2. The reaction of thiophenol with methyl crotonate was catalyzed by 14 and lithium thiophenolate to afford (S)-methyl 3-phenylthiobutanoate in 75% ee and 95% yield.

Chiral ligand-controlled catalytic asymmetric epoxidation of α,β-unsaturated carbonyl compounds with peroxide

Abstract Asymmetric epoxidation reaction of α,β-unsaturated carbonyl compounds with alkylperoxide was catalyzed by an external chiral tridentate aminodiether–lithium peroxide giving epoxides with good enantiomeric excess. Slow addition of alkylhydroperoxide was beneficial for a catalytic asymmetric reaction. Lone pair electron-differentiating coordination of a carbonyl oxygen to lithium is another critical factor for high enantioselectivity.

Asymmetric Michael–aldol tandem cyclization of ω-oxo-α,β-unsaturated esters with 10-mercaptoisoborneol methyl ether

Abstract The asymmetric reaction of ω-oxo-α,β-unsaturated esters with lithium chiral thiolates afforded the Michael–aldol tandem cyclization products in high yield and good stereoselectivity. Reductive desulfurization gave the corresponding optically pure 2-hydroxycycloalkanecarboxylates.