Highly Selective Generation and Application of (E)- and (Z)-Silyl Ketene Acetals from α-Hydroxy Esters

Article abstract of DOI:10.1021/jo00072a005

A method for the stereoselective synthesis of silyl ketene acetals from α-hydroxy esters is described.Internal quench with excess TMSCl of the lithium enolate at -100 deg C, which is generated using a hindered base, LTMP, leads to the selective formation of (E)-silyl ketene acetal.In contrast, the deprotonation t -100 deg C using LHMDS in THF-HMPA (4:1), followed by treatment with tert-butyldimethylsilyl chloride affords the (Z)-silyl ketene acetal selectively.The method can be applied to the stereoselective reaction of the Ireland ester enolate Claisen rearrangement and aldol synthesis.