Results obtained in the reactions of Et 2 AlCN with exocyclic, endocyclic, and acyclic α-ptolylsulfinyl ketimines are reported. Good conversions and satisfactory stereochemical results are obtained exclusively from cyclic ketimines. Imine-enamine equilibrium accounts for the incomplete conversions and low reactivities observed for acyclic amines. Configurational assignments and mechanistic proposals are based on the conformational analysis of substrates and products.