Regiospecific synthesis of aza-.beta.-lactams from diaziridines

1,3-Diazetidinones are obtained by bis(dibenzylideneacetone)palladium(0)-catalyzed carbonylation of diaziridines having one substituent attached to the ring carbon atom. This regiospecific insertion into the nitrogen-nitrogen bond also occurs for 3,3-disubstituted diaziridines, provided one uses stoichiometric quantities of cobalt carbonyl.