Unusual Regioselectivity in the Gold(I)-Catalyzed [3+2] Carbocycloaddition Reaction of Vinyldiazo Compounds and N-Allenamides

The reaction of N-allenamides with alkenyl diazo compounds in the presence of gold catalysts provided methylidenecyclopentene derivatives resulting from a formal intermolecular [3+2] carbocyclization, a rare process in the gold chemistry of allenes. The participation of the CC bond of the allenamide represents a very unusual regioselectivity in gold-catalyzed cycloaddition reactions of this type of allenic scaffolds. A stepwise mechanism involving initial activation of the diazo component has been proposed.