Synthesis of 2-Halogenated Quinolines by Halide-Mediated Intramolecular Cyclization of o-Alkynylaryl Isocyanides

When o-alkynylaryl isocyanides 1 are treated with triethylamine in chloroform, intramolecular chlorinating cyclization of the isocyanides takes place, affording the corresponding 2-chlorinated quinoline derivatives 2 in good to excellent yields, selectively. Bromoform can be also used for the brominating cyclization of 1. Furthermore, fluorinating and iodinating cyclization of o-alkynylaryl isocyanides has been attained by the selection of fluoride and iodide (ion) sources.