Inversion of stereochemistry in the Co2(CO)8-catalyzed carbonylation of aziridines to β-lactams. The first synthesis of highly strained trans-bicyclic β-lactams
β-Lactams were synthesized by the carbonylative ring expansion of aziridines catalyzed by dicobalt octacarbonyl under CO pressure. The active catalyst, cobalt tetracarbonyl anion, induces nucleophilic ring opening of the heterocycle, resulting in inversio