Palladium-Catalyzed C3-Carbaldehyde Directed Regioselective C2-Thioarylation of Indoles

Abstract

Palladium-catalyzed thioarylation of indoles by diaryl disulfides in the presence of phenyliododiacetate is reported. The directing potential of weakly coordinating aldehyde group present at 3-position of indole was exploited for regioselective C2-H thioarylation over the possible C4-H functionalization. Mechanistic studies reveal that the process involves initial generation of thioaryl radical followed by sequential C-H activation, thiolate transfer, and reductive elimination.

Keywords: Carbaldehyde directing group; Indole; Pd-catalysis; Selective C2-H functionalization; diaryl disulfides.