Design and Development of Carbene-Catalyzed Intramolecular Vinylogous Stetter Reaction to Access Phenanthrol Derivatives

The present study reveals the design and development of an N-heterocyclic carbene (NHC)-catalyzed intramolecular vinylogous Stetter reaction. This protocol enabled the synthesis of diverse phenanthrol derivatives and naphthol-fused heterocycles in very good to excellent yields. The success of the title reaction relies on the design of biaryl aldehydes bearing <i>p</i>-quinone methide (<i>p</i>-QM) moiety that acts as a vinylogous Stetter (1,6-conjugate) acceptor while the aldehyde functional group serves as an acyl anion equivalent, generated in situ from NHC-catalyzed umpolung. Salient features of the presented protocol include atom efficiency, operational simplicity, broad substrate scope, large-scale synthesis, and postsynthetic modifications.