Gallium(III)-Promoted Halocyclizations of 1,6-Diynes

Cyclization of 1,6-diynes promoted by stoichiometric Ga­(III) halides produces vinyl halides in good to excellent yields. Under acidic conditions, initially formed iodocyclization products undergo in situ Friedel–Crafts cyclizations, giving access to iodoindenopyridines. Application of the vinyl halides in cross-coupling reactions has been explored, and mechanistic aspects of the cyclization are discussed.