Silica-grafted DBU-supported NiCl2: a sustainable heterogeneous catalyst for A3 coupling

Silica-grafted DBU-supported NiCl2 complex, 1-(3-((3-(silica-trioxysilyl) propyl) amino) propyl) azepan-2-one nickel chloride (SiO2@DBU-NiCl2), has been designed and synthesized by multistep approach and characterized by FT-IR, XRD, EDS, FE-SEM, TGA and XPS. Catalytic activity of SiO2@DBU-NiCl2 has been explored for A(3) coupling of terminal alkynes, aldehydes and secondary amines resulting in excellent yields (up to 97%). Special features of present protocol are high TONs (625-1212) and TOFs (52-404), low catalyst loading (0.08 mol %), solvent-free conditions, facile recyclability and reusability of the catalyst (up to 5 times).

Automated summary

A silica-grafted DBU-supported NiCl2 complex, SiO2@DBU-NiCl2, was synthesized and characterized. The catalytic activity of SiO2@DBU-NiCl2 was explored for A(3) coupling of terminal alkynes, aldehydes, and secondary amines, resulting in high yields (up to 97%). The protocol exhibited high TONs (625-1212) and TOFs (52-404), low catalyst loading (0.08 mol%), solvent-free conditions, and facile recyclability and reusability of the catalyst (up to 5 times).