A Top‐Down Approach to Synthesis of pH‐Controlled Cu NPs: Their Catalytic Activity toward the One‐Pot Preparation of α‐Aminonitriles and 5‐Substituted 1H‐Tetrazoles from Aldehydes.

A new approach for the preparation of copper nanoparticles has been developed by the chemical decomposition of bulk‐waste copper wire using HNO3/ DMSO/ NaOCl (HDN) reagent. This is a two‐steps synthesis via a top‐down approach for the preparation of NPs. A mixture of Cu NPs was obtained in high basic pHs (>12) including CuO, Cu(OH)2 and Cu2(OH)3Cl NPs. The Cu NPs demonstrated high dependent on pH, which each of copper NPs were selectively prepared with pH control. Selective preparation of copper NPs lead to pure Botallackite Cu2(OH)3Cl, Cu(OH)2, and Tenorite CuO structures at pH =7, pH<7, and pH=11 respectively. The mixture and pure copper NPs were thoroughly characterized by various analytical techniques including XPS, EDX, XRD, DLS, FTIR, FE‐SEM, TEM, BET, and ICP methods. The resultant Cu NPs were used as an efficient heterogeneous, recyclable nanocatalyst for the preparation of α‐aminonitriles and 5‐substituted 1H‐tetrazoles with a synergistic effect. The nanocatalyst not only demonstrated high to excellent yields for the aminonitriles and tetrazoles under mild conditions, but also it can be recovered and reused for several times without considerable loss in activity. Kinetics for the preparation of α‐aminonitrile and 5‐substituted 1H‐tetrazole was studied and chemoselectivity of the method was evaluated by various combinations. [ABSTRACT FROM AUTHOR]