Chiral Sulfur Compounds. XV. Diastereoselective Additions of Lithiated S-Benzyl-N-t-butyldiphenylsilyl-S-methyl-sulfoximine to Imines and Aldehydes

Abstract

The lithium salt of racemic S-benzyl-N-t- butyldiphenylsilyl-S-methylsulfoximine (2) undergoes 1,2-addition to imines that have been activated by precomplexation with boron trifluoride diethyl etherate (BF₃.Et₂O), and aldehydes , with high diastereoselectivity. The relative lS*,2S.*,S*s stereochemistry of the major diastereomeric adducts of (2) and EtCH = NPh and PrⁱCH = NPh , and the relative lS *,2S*,S*s stereochemistry of the major diastereomeric adduct of (2) and propanal were unequivocally determined by single-crystal X-ray structure analysis. An open transition state has been proposed to account for the stereochemical outcome of these reactions.