Pd(0)-Catalyzed Dearomative Diarylation of Indoles

Abstract

We have developed a protocol for a Pd(0)-catalyzed dearomative syn 1,2-diarylation of indoles using readily available boroxines (dehydrated boronic acids) as coupling partners. This reaction proceeds efficiently using PtBu3 as the ligand to divergently access to fused indolines while minimizing the extent of direct Suzuki coupling. The scope of the reaction is remarkably broad and all products are obtained as single diastereomers in moderate to excellent yields. We have also compiled data which parallels the steric and electronic properties of both substrate and boroxine with the propensity to undergo the desired dearomative process over direct Suzuki coupling.

Keywords: C−C coupling; diastereoselectivity; heterocycles; homogeneous catalysis; palladium.