Electrochemical Oxidative Dearomatization of Indole with Carboxylic Acid via 1,2-Acyloxy Migration for the Synthesis of C2-Quaternary Indolin-3-ones

Herein, we develop an efficient KBr-promoted electrochemical strategy that enables the oxidative dearomatization of indoles with carboxylic acids via 1,2-acyloxy migration, establishing a mechanistically different method to synthesize structurally diverse C2-quaternary indolin-3-ones using H2O as an oxygen atom source. This metal- and chemical-oxidant-free protocol proceeds in an undivided cell, exhibiting a broad substrate scope and good functional group tolerance. Mechanistic investigations, including control experiments and isotope-labeling studies, support a C-3 esterification/1,2-acyloxy migration cascade pathway.