“On Water” Direct and Site‐Selective Pd‐Catalysed CH 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.