Cupric Halide-Mediated Intramolecular Halocyclization of N-Electron-Withdrawing Group-Substituted 2-Alkynylanilines for the Synthesis of 3-Haloindoles

A convenient and efficient method for the synthesis of 3-haloindoles has been developed. Both 3-chloro- and 3-bromoindole derivatives can be obtained in high yields by the reaction of N-electron-withdrawing group-substituted 2-alkynylanilines with cupric halide in dimethyl sulfoxide (DMSO) within a short period of time. Investigation of the reaction mechanism reveals that two equivalents of cupric halide are necessary.