Cu(II)–Hydromagnesite Catalyzed Synthesis of Tetrasubstituted Propargylamines and Pyrrolo[1,2-a]quinolines via KA2, A3 Couplings and Their Decarboxylative Versions

A novel copper supported on hydromagnesite (Cu/HM) nanomaterial was prepared by a simple impregnation method at room temperature and characterized by PXRD, SEM, TEM, EDAX, XPS, ICP-AES and FT-IR techniques. The EDAX and XPS results revealed the presence of 8.82 wt % of copper in (+2) oxidation state. Three-component coupling of ketone and amine with alkyne to afford tetrasubstituted propargylamine is known as KA2 coupling, whereas the three-component reaction of aldehydes and amine with alkyne to give propargylamine is considered as an A3-coupling reaction. The Cu/HM was found to be an efficient heterogeneous catalyst for KA2 coupling reaction under solvent free condition, and A3 coupling strategy to afford the pyrrolo[1,2-a]quinolines in DEG as a green solvent. The high catalytic activity of Cu/HM in the A3 coupling strategy to afford propargylamine intermediate is due to the synergistic effect of both Cu2+ and Mg2+ active sites. The versatility of Cu/HM catalyst was also studied for the decarboxylative ...