The effects of amines on oxidative homo-coupling of terminal alkynes promoted by copper salts

Abstract

The effects of all kinds of amines on homo-couplings (Glaser reactions) of terminal alkynes promoted by copper salts and the Sonogashira coupling reactions were studied systematically. Diethylamine (2° amine) can serve as an excellent solvent, base and coordination ligand in the oxidative homo-coupling of terminal alkynes and several modified Glaser coupling procedures have been developed which are based on a catalytic amount of cuprous salts (CuI, CuBr or CuCl) with diethylamine systems. Homo-coupling of terminal acetylenes in the Sonogashira reaction could be inhibited by using triethylamine (3° amine) as reaction medium, and the cross-coupling products were formed as the exclusive products.