Rhodium(I)-Catalyzed Coupling-Cyclization of C═O Bonds with α-Diazoketones.

An unprecedented intermolecular nucleophilic attack of C═X bonds (X = O and S) on the rhodium(I)-carbenes has been developed. This transformation allows for the coupling-cyclization of aroylamides with α-diazoketones and provides concise access to 2,4,5-trisubstituted 1,3-oxazoles and 1,3-thiazoles with a broad tolerance of functional groups.