Synthesis of benzodiazepine-containing polyheterocyclic compounds via C–H bond activation-initiated formal [5 + 2] annulation

Abstract

The development of innovative strategies for the synthesis of medium-sized N-heterocyclic compounds is an important yet challenging topic in organic synthesis. Presented herein is a novel synthesis of benzodiazepine-containing polyheterocyclic compounds bearing a synthetically valuable vinyl substituent via C–H bond activation-initiated formal [5 + 2] annulation of 2-(indolin-1-yl)-1H-benzo[d]imidazoles with vinyl-1,3-dioxolan-2-one. Mechanistically, the formation of the product proceeds through an intriguing pathway involving indoline C7–H bond activation/metalation, vinyl insertion, β-oxygen elimination, and decarboxylation, followed by another sequence of vinyl insertion and β-oxygen elimination. In general, this reaction is compatible with a broad range of substrates bearing different kinds of functional groups and features excellent atom- and step-economy. Moreover, the value of this novel protocol was showcased by gram-scale preparation and versatile functional group interconversions.