Scalable Rhodaelectro-Catalyzed Expedient Access to Seven-Membered Azepino[3,2,1-hi]indoles via [5 + 2] C–H/N–H Annulation

Abstract

We report the establishment of a rhodaelectro-catalyzed [5 + 2] N–H/C–H oxidative annulation of alkynes by 7-arylindoles, enabling the synthesis of seven-membered azepino[3,2,1-hi]indoles using electricity as the sole oxidant. The reaction could be scaled up to gram-scale by flow-electrocatalysis. Two key rhodium(III) intermediates were isolated and fully characterized. Cyclovoltammetric analysis, X-ray photoelectron spectroscopy studies, and density functional theory calculations are suggestive of a rhodium(III–IV–II–III) manifold.