A Rh-Catalyzed Cycloisomerization/Diels-Alder Cascade Reaction of 1,5-Bisallenes for the Synthesis of Polycyclic Heterocycles.

A novel methodology to transform bisallenes into a variety of polycyclic derivatives employing rhodium(I) catalysis has been developed. This transformation encompasses an intramolecular Rh-catalyzed cycloisomerization of bisallenes 1 to deliver a reactive cycloheptadiene, which concomitantly undergoes a regioselective [4 + 2] cycloaddition with alkenes. A complete mechanistic study of this transformation has been undertaken including DFT calculations. Overall, the methodology presented here constitutes a new and straightforward entry to polycyclic dihydroazepine and dihydrooxepine derivatives employing catalytic methods.