<i>N</i>-Alkylation-Initiated Redox-Neutral [5 + 2] Annulation of 3-Alkylindoles with <i>o</i>-Aminobenzaldehydes: Access to Indole-1,2-Fused 1,4-Benzodiazepines

Abstract

Described herein is an unprecedented <i>N</i>-alkylation-initiated redox-neutral [5 + 2] annulation of 3-alkylindoles with <i>o</i>-aminobenzaldehydes via a cascade <i>N</i>-alkylation/dehydration/[1,5]-hydride transfer/Friedel-Crafts alkylation sequence. A series of indole-1,2-fused 1,4-benzodiazepines are facilely constructed in moderate to good yields in one step. This protocol features excellent regioselectivity, metal-free conditions, high step economy, and wide substrate scope.