Diastereoselective Chelation-Controlled Additions to β-Silyloxy Aldehydes

A general diastereoselective method for the addition of dialkylzincs and (<i>E</i>)-di- and (<i>E</i>)-trisubstituted vinylzinc reagents to β-silyloxy aldehydes is presented. This method employs alkyl zinc triflate and nonaflate Lewis acids and affords chelation-controlled products (6:1 to > 20:1 dr)