Synthesis and Characterization of Cucurbit[6]uril Supported Copper Oxide Nanoparticles, CuO@CB[6]: Application as Nanocatalyst for the Synthesis of 2H‐indazoles.

Fine nanoparticles of CuO, generated in‐situ by the chemical reduction method, were immobilized on cucurbit[6]uril support to afford nanocomposite CuO@CB[6] as an air‐stable green powder. The nanocomposite was fully characterized by various physicochemical techniques, such as FTIR, PXRD, XPS, FESEM, EDX, Elemental mapping, HRTEM, TGA, and ICP‐AES. It has been found to be an efficient heterogeneous nanocatalyst for the synthesis of a series of 2H‐indazoles from aldehyde, amine, and azide, under base‐ and ligand‐free conditions, at a low concentration of the metal (0.2 mole %). The augmented catalytic activity of the CuO NPs is attributed to the fine size of the nanoparticles. The nanocatalyst was retrieved from the reaction mixture by simple filtration and reused up to five times with insignificant deprivation in its catalytic activity. All synthesized 2H‐indazoles were isolated in good to excellent yield (55‐96%) and characterized by 1H and 13C NMR studies. Three new indazoles are additionally characterized by DEPT 135 spectroscopy and HRMS spectra. [ABSTRACT FROM AUTHOR]