New Diimine−Copper Complexes: An Efficient and Simple Catalyst System for Buchwald N-Arylation of Indole

A new method of N -arylation of indole with (±)- trans -2,3-diarylpiperazines/copper(I) halide and aryl halides is described. Whereas electron-donating substituents in the phenyl group enhance the reactivity, the yields are lower with electron-withdrawing substituents. Oxidative cleavage of piperazines in the presence of oxygen to diimines has been observed under these reaction conditions. On the basis of this observation, a new catalyst system using diimines and CuI was also developed for the N -arylation of indole.