Efficient three-component coupling catalysed by mesoporous copper-aluminum based nanocomposites

Traditional synthesis methods for propargylamines have several drawbacks. A recently developed alternative route is the so-called "A(3) coupling" in which an alkyne, an aldehyde, and an amine are coupled together. Typically, these reactions are catalysed by homogeneous gold salts, organogold complexes or silver salts. But these homogeneous catalysts are expensive and their separation is difficult. Here we report the discovery that solid Cu/Al/oxide mesoporous "sponges" are excellent A(3) coupling catalysts. These materials are robust, inexpensive, and easy to make. They give good to excellent yields (87-97%) for a wide range of substrates. Being heterogeneous, these catalysts are also easy to handle and separate from the reaction mixture, and can be recycled with no loss of activity.