Synthesis of [Zn()BHPPDAH] as New Heterogeneous Catalyst without Being Immobilized on Any Support and Applied for Mannich Reaction

In this paper, a novel heterogeneous complex of zinc with N,N-bis(2-hydroxyphenyl)pyridine-2,6-dicarboxamide(BHPPDAH) was synthesized. The catalyst was found to be a highly effective catalyst for the three-component coupling reactions of aldehydes, alkynes, and amines (A3 coupling) via C-H activation. The reactions could be applied to both aromatic and aliphatic aldehydes and alkynes. Nearly quantitative yields of the desired products were obtained in most cases. The reaction proceeds without any cocatalyst or activator, and water is the only byproduct. The catalyst was quantitatively recovered from the reaction by a simple filtration and reused for five cycles with almost consistent activity.