Asymmetric Aldol Additions: Use of Titanium Tetrachloride and (−)-Sparteine for the Soft Enolization of <i>N-</i>Acyl Oxazolidinones, Oxazolidinethiones, and Thiazolidinethiones
作者:Michael T. Crimmins、Bryan W. King、Elie A. Tabet、Kleem Chaudhary
DOI:10.1021/jo001387r
日期:2001.2.1
N-methyl-2-pyrrolidinone, selectivities of 97:3 to > 99:1 were obtained for the Evans syn aldol products using N-propionyl oxazolidinones, oxazolidinethiones, and thiazolidinethiones. The non-Evans syn aldol adducts are available with the oxazolidinethione and thiazolidinethiones by altering the Lewisacid/aminebase ratios. The change in facial selectivity in the aldoladditions is proposed to be a result of