Electrochemical functionalization of indoles represents an efficient and green strategy for the synthesis of indole derivatives. Herein, we report for the first time an electrochemical C3 acyloxylation reaction of 2-arylindoles. This radical acyloxylation reaction uses tetrabutylammonium carboxylates as both the acyloxy sources and the electrolytes, affording acyloxylated indoles as products in moderate to excellent yields under catalyst- and oxidant-free conditions. Mechanistic studies disclose that this reaction proceeds via anodic oxidation of the indole to form a radical cation, followed by direct coupling with a carboxylate anion and subsequent deprotonation. The transformation features mild conditions, broad substrate scope, and scale-up applicability, which provides a new and green strategy for the synthesis of 3-acyloxyindoles.

Key words: 2-arylindoles, acyloxylation, electrochemical reaction, radical reaction, tetrabutylammonium acetate