Novel Catalytic and Stoichiometric Approaches to Azetidine-2,4-diones from -Lactams Using Rhodium and Cobalt Complexes, Respectively.

Although α-lactams are regiospecifically converted to azetidine-2,4-diones in fine yields with use of rhodium(I) [e.g., [Rh(CO)2Cl]2] and cobalt(0) [e.g., Co2(CO)8] complexes, the two processes are significantly different: the rhodium reaction occurs under carbon monoxide and is catalytic; the cobalt reaction is inhibited by carbon monoxide and is not catalytic.