Synthesis of 3-Halo-7-azaindoles through a 5-endo-dig Electrophilic Cyclization Reaction

Biologically useful 7-azaindoles were synthesized by electrophilic cyclization of 3-alkynyl- N , N -dimethylpyridine-2-amines with molecular iodine. By this simple atom-economical approach under ambient reaction conditions, a library of interesting 3-iodo-7-azaindoles were synthesized in high yields. To synthesize the corresponding 3-bromo- and 3-chloro-7-azaindoles, an environmentally benign copper-mediated cyclization was employed, with inexpensive, nontoxic, and noncorrosive sodium chloride and sodium bromide as the sources of chlorine and bromine, respectively.