Exceptionally Mild Palladium(II)-Catalyzed Dehydrogenative C–H/C–H Arylation of Indolines at the C-7 Position under Air

Abstract

An improved method for the dehydrogenative C-H/C-H cross-coupling at the C-7 position of indolines containing a urea as a directing group is reported. The new protocol is a rare example of an aerobic palladium(II)-catalyzed cross dehydrogenative coupling (CDC) reaction that proceeds at low temperature. The use of either Cu(OAc)2 in an open flask or dioxygen (balloon) at 50 °C tolerates indolines not substituted at C-2 and C-3, thereby extending the scope of the previous method that suffers from indoline-to-indole oxidation.