Stereoselective Synthesis of Trisubstituted (Z)-Alkenes from Ketones via the Julia-Kocienski Olefination Using 1-Methyl- and 1-tert-Butyl-1H-tetrazol-5-yl Alkyl Sulfones

1-Methyl-1H-tetrazol-5-yl (MT) alkyl sulfones 1b, 3b, and 7b react with various unsymmetrical ketones in the presence of LiHMDS in THF at low temperature to give trisubstituted (Z)-alkenes in good yields stereoselectively (Z/E = 91:9 to 99:1). For sterically less demanding ketones, olefination using t-Bu reagents 1d and 3d generated (Z)-alkenes with higher stereoselectivity (93:7-99:1).