Au(III) catalyst supported on a thermoresponsive hydrogel and its application to the A-3 coupling reaction in water

Poly(NIPAM-co-4-VP), synthesized from N-isopropylacrylamide and 4-vinylpyridine with a 1:1 monomer ratio, exhibits a temperature-dependent phase transition in water with a low critical solution temperature (LCST) of 47 degrees C. Coordination of Au(III) with the polymer results in material with metal catalytic activity combined with the inverse solubility phenomenon of the polymer, which catalyzes the three-component coupling reaction of aldehydes, amines, and alkynes in water with excellent yields. The polymer not only functions as a supporter for Au(III) but also accelerates the catalysis by undergoing a coil-to-globule phase transition above the LCST. The catalyst is efficient, is stable in air, and tolerates a variety of substrates. Moreover, the recyclability of the catalyst makes it eco-friendly and economical to use. (C) 2014 Elsevier Inc. All rights reserved.