Gold-Catalyzed Synthesis of Furo[3,4-c]-azepines

Significance

Reported is a new approach to ­furo[3,4-c]azepines from acyclic precursors using gold catalysis. The reaction has been optimized with respect to catalyst and solvent, with other combinations affording lower yields. The yields are mostly good and the substrate scope was well studied. Interestingly, in most cases only a single diastereomer is obtained. As to the mechanism, the reason for formation of the 5,7-fused hetero­bicyclic structure rather than the expected 5,5-fused one is not clear.