On Water Direct and Site-Selective Pd-Catalysed C-H Arylation of (NH)-Indoles

This communication describes the development of a versatile catalytic system based on palladium(II) acetate/bis(diphenylphosphino) methane [Pd(OAc)(2)/dppm] that works on water giving site-selective C-H arylation of (NH)-indoles without protecting or directing groups. Remarkably, the control of regioselectivity was achieved by small changes in the extra-catalytic base/halide partners. These innovative methodologies allow a high-yielding access to both C2 and C3-arylindoles, as well as 2,3-diarylindoles, and display high chemo/regioselectivities and structural versatility with regard to either indole or aryl moieties.