Synthesis of Benzofused N-Heterocycles via Rh(III)-Catalyzed Direct Benzannulation with 1,3-Dienes

Abstract

Benzofused nitrogen heterocycles are prevalent as key core structural motifs in functional molecules. Major syntheses of benzofused nitrogen heterocycles focus on construction of the heterocyclic ring starting from (poly)substituted benzene derivatives. Given that polysubstituted benzene derivatives are not always easily available, the flexibility of these methods may be problematic. The direct benzannulation reactions of simple N-heterocycles thus provide a complementary and valuable strategy. However, this approach has been far less explored, especially when nonprefunctionalized N-heterocycles are used as starting materials. In recent years, the metal-catalyzed direct functionalization of an inert C–H bond has become a powerful tool to construct (hetero)aromatics. In the C–H benzannulation reactions, alkynes, activated alkenes, enaldiazo compounds, and biaryl compounds were previously utilized as efficient coupling partners. Reported herein is a de novo synthesis of a benzene ring through the rhodium-ca...