Regiocontrolled Annulation of Benzocyclobutenols with Alkynes.

A tandem reaction that involves an unprecedented Rh-catalyzed intramolecular annulation of benzocyclobutenols with alkynes and subsequent ZnCl2-promoted dehydration was developed, offering an efficient approach to 2H-furan-, pyran-, and oxepine-fused naphthalenes. Furthermore, the 2H-furan motif may undergo a ring-opening reaction through Fe-catalyzed reductive C-O bond cleavage. As a consequence, the formal intermolecular annulation of 2-hydroxybenzocyclobutenols with alkynes was realized with complete regioselectivity through a two-step protocol.

Skeleton Reorganization of Substituted Benzocyclobutenols through Rh-Catalyzed C-C Bond Cleavage Manipulated by Hydrogen Transfer.

Although transition-metal-catalyzed C-C bond activation has been investigated extensively, C-C bond cleavage manipulated by hydrogen transfer has been unexplored. In this work, we disclose a skeleton reorganization of alkene-tethered benzocyclobutenols through Rh-catalyzed C-C bond cleavage coupled with intra- and intermolecular hydrogen transfer. The reaction pathway was well-tuned by the catalytic systems. As a result, divergent benzofurans bearing 4-ß-hydroxy or 4-ß-keto moieties were synthesized under pH- and redox-neutral conditions.