Stereoselective synthesis of highly substituted gamma-lactams by the [3+2] annulation of alpha-siloxy allylic silanes with chlorosulfonyl isocyanate.

[reaction: see text] A stereoselective synthesis of gamma-lactams by the [3+2] annulation of alpha-siloxy allylic silanes with N-chlorosulfonyl isocyanate (ClSO(2)NCO) was developed. The use of these allylic silanes allowed for further diastereoselective substitution of the resultant N,O-acetal to give highly substituted gamma-lactams. Oxidation of the silyl group afforded access to complex beta-hydroxy-gamma-lactams.