Polystyrene supported N-phenylpiperazine–Cu(II) complex: an efficient and reusable catalyst for KA2-coupling reactions under solvent-free conditions

A new polystyrene supported N-phenylpiperazine–Cu(II) complex 4c was found to be an efficient, simple, versatile catalyst for the selective multicomponent reaction of terminal alkynes, ketones, and secondary amines to give the corresponding propargylamines. The coupled products were formed in excellent yields at low catalyst loadings (0.2 mol% of metal) under solvent free conditions at 110 °C. Further, this heterogeneous catalyst showed excellent recyclability without any significant loss in its activity for up to five times of cycling.