Efficient construction of indole rings from 2-ethynylaniline derivatives catalyzed by copper(II) salts and its application to the tandem cyclization reactions

The efficient cyclization reactions of the N-methanesulfonyl or N-ethoxycarbonyl derivatives of 2-ethynylanilines, functionalized on the benzene ring and/or the acetylene terminal into indoles catalyzed by either Cu(OTf)2 or Cu(OAc)2 are accomplished. The application of this reaction to the tandem cyclization reaction is also described.