One-pot synthesis of 6H-benzo[c]chromene and 6,7-dihydrodibenzo[b,d]oxepine through dearomatization and dienone–phenol rearrangement

Abstract

Herein, a one-pot synthetic strategy using PIFA- and Ga(OTf)₃-promoted spirocyclization and ring expansion reactions for the construction of 6H-benzo[c]chromene and 6,7-dihydrodibenzo[b,d]oxepine scaffolds is reported. Didehydroconicol, a natural product with a core tricyclic skeleton, is successfully synthesized via this methodology. The DFT calculations reveal that the formation of the 2-hydroxyl products involves a three membered ring transition state via a phenyl migration process, which is kinetically more favorable than the O atom migration pathway.