Solvent-Free A3 and KA2 Coupling Reactions with mol ppm Level Loadings of a Polymer-Supported Copper(II)–Bipyridine Complex for Green Synthesis of Propargylamines

Abstract

A copper(II)–bipyridine complex immobilized on amphiphilic polystyrene–poly(ethylene glycol) (PS–PEG) resin (PS–PEG-BPy–CuBr2) has been developed. The immobilized copper(II)–bipyridine complex at a mol ppm level of loading efficiently catalyzed the three-component coupling of aldehydes or ketones, amines, and alkynes (A3 or KA2 coupling) under solvent-free conditions to give the corresponding propargylamines in good-to-excellent yields. Moreover, 10 g-scale green syntheses of propargylamines proceeded with excellent atom economy (E factor ≥ 0.38) through a solvent-free A3 coupling using 5 mol ppm of PS–PEG-BPy–CuBr2. The total turnover number and turnover frequency of the catalyst reached as high as 178 800 and 7450 h–1, respectively.