Cu(II)-Catalyzed direct and site-selective arylation of indoles under mild conditions

We have developed a new site-selective Cu(II)-catalyzed C-H bond funtionalization process that can selectively arlate indoles at either the C3 or C2 position under miled conditions. The scope of arylation process is broad and tolerates broad functionality on both indole and aryl unit, which makes it amenable to further elaboartion. The mechanism of the arylation reaction is proposed to proceed via a Cu(III)-aryl that undergoes intial addition at the C3 position of the indole motif. We speculate that site of indole arylation arises through a migration of the Cu(III)-aryl group of C3 to C2, and this can be controlled by the nature of the group on the nitrogen atm; free (NH)-and N-alkylindoles deliver the C3-arylated product, whereas N-acytylindoles affored the C2 isomer, both with excellent yield and selectivity.