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

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journal contribution
posted on 13.04.2016, 00:00 by U. Chinna Rajesh, Upasana Gulati, Diwan S. Rawat
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 A3 and KA2 coupling strategies. The present method offers several advantages such as simple procedure for the catalyst preparation, versatile catalytic applications, cheap precursors, higher yield of products in short reaction time, recovery and reusability of the catalyst.