Direct Synthesis of Benzo[<i>c</i>]carbazoles by Pd-Catalyzed C–H [4 + 2] Annulation of 3-Arylindoles with External 1,3-Dienes

Abstract

Herein, we present a regioselective Pd-catalyzed C-H [4 + 2] benzannulation of <i>N</i>-unprotected 3-arylindoles with external readily available 1,3-dienes via an original sequence involving a Pd-catalyzed domino carbopalladation of 1,3-dienes/direct C₂-H allylation of an indole ring followed by an oxidation or reduction step. Depending on the nature of the solvent, DCE or CH₃CN, two consecutive approaches, oxidative or reductive, have been validated and applied to the design of a novel library of C₆-alkyl or (<i>E</i>)-C₆-styryl-benzo[<i>c</i>]carbazoles in moderate to good yields.