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

•Au(III) catalysts dispersed on poly(NIPAM-co-4-VP) hydrogel.•Heterogeneous Au(III) catalyst showed high catalytic activities for A3-coupling reaction in water.•The immobilized Au(III) catalyst showed an excellent recyclability and excellent yield.

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 °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.

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