Redox-Neutral Assembly of Diheteroarylalkanes via Transient Directing Group-Enabled C-H Methylenation

Abstract

We report transition-metal-free homocoupling of quinolines and cross-coupling between quinolines and indoles via regioselective C(sp²)–H methylenation using Eschenmoser’s salt, providing direct access to two classes of diheteroarylalkanes. Mechanistic studies unveil an electronically modulated transient directing role of the tert-butyl group, enabling a dearomatization-addition-rearomatization cascade. This strategy features broad substrate scope, redox-neutral conditions, and high step economy, establishing the first general application of Eschenmoser’s salt for heteroarene C–H functionalization.