Palladium‐catalyzed sequential Heck/Suzuki coupling reaction and the synthesis of diarylmethanes in aqueous media using indole‐based N‐heterocyclic carbene precursors

Abstract

This study introduced a versatile class of indole‐based benzimidazolium salts, offering distinct advantages: (1) the utilization of affordable and easily accessible starting materials; (2) a straightforward and uncomplicated synthesis process; (3) the diversity of the salt should provide fine‐tunability of steric and electronic properties. These salts, employed as N‐heterocyclic carbene (NHC) precursors, were effectively utilized in the Pd‐catalyzed C–C bond formation reactions involving aryl or benzyl halide. The catalytic system, arising from the in situ generation of Pd(OAc)2 and indole‐based benzimidazolium salts, demonstrated remarkable efficiency. It accomplished the synthesis of diarylmethanes via the Suzuki coupling of benzyl chlorides and arylboronic acids in aqueous media with a Pd loading of 0.5 mol%. Furthermore, it successfully achieved the one‐pot sequential Heck/Suzuki coupling reactions with a Pd loading of as low as 0.25 mol%.