New diimine-copper complexes: An efficient and simple catalyst system for buchwald N-arylation of indole

Abstract

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. © 2008 American Chemical Society.