Palladium-Catalyzed Regioselective Synthesis of 1,2-Fused Indole-Diazepines via [5+2] Annulation of o-Indoloanilines with Alkynes

Abstract

An efficient and regioselective palladium(II)-catalyzed [5+2] annulation of unprotected o-indoloanilines with internal alkynes under microwave irradiation has been explored. The diverse imine-containing 1,2-fused indole[1,7-a]diazepines are constructed in moderate to excellent yields. The mechanistic pathway shows pivalic acid and molecular oxygen to play crucial roles for the regeneration of highly active electrophilic palladium species in the catalytic cycle.