Stereoselective Synthesis of Highly Substituted γ-Lactams by the [3+2] Annulation of α-Siloxy Allylic Silanes with Chlorosulfonyl Isocyanate

A stereoselective synthesis of γ-lactams by the [3+2] annulation of α-siloxy allylic silanes with N-chlorosulfonyl isocyanate (ClSO2NCO) was developed. The use of these allylic silanes allowed for further diastereoselective substitution of the resultant N,O-acetal to give highly substituted γ-lactams. Oxidation of the silyl group afforded access to complex β-hydroxy-γ-lactams.