Copper(I) chloride catalysed room temperature C-sp-C-sp homocoupling of terminal alkynes mediated by visible light

We developed a technique mediated by visible light for the aerobic homocoupling of terminal alkynes to synthesize 1,3-conjugated diynes using a copper(I) chloride catalyst at room temperature. Compared with previously reported thermal processes, this photochemical method is simple, uses only mild reaction conditions, produces high yields and works well for substrates with electron-withdrawing groups without the need for bases/ligands, oxidants or palladium catalysts.