Practical Oxidative Homo- and Heterocoupling of Terminal Alkynes Catalyzed by Immobilized Copper in MCM-41

A practical oxidative homo- and heterocoupling of terminal alkynes was achieved in CH2Cl2 at 25 degrees C by using a 3-(2-aminoethylamino)propyl-functionalized MCM-41-immobilized copper(I) complex (MCM-412N-CuI, 1 mol-%) as the catalyst, piperidine (0.1 or 3 equiv.) as the base, and air as the environmentally friendly co-oxidant, yielding a variety of symmetrical and unsymmetrical 1,4-disubstituted 1,3-diynes in good to excellent yields. This heterogeneous copper catalyst showed a higher catalytic activity than CuI and can be recovered and recycled by a simple filtration of the reaction mixture and used for at least 10 consecutive runs without any decrease in activity.