Palladium nanoparticles supported on organofunctionalized kaolin as an efficient heterogeneous catalyst for directed C–H functionalization of arylpyrazoles

Abstract

A heterogeneous catalyst system based on the immobilization of Pd⁰ nanoparticles onto organofunctionalized kaolin is reported with a view to introducing new synthetic routes of directed C–H functionalization of arylpyrazoles. Various characterization techniques revealed that the functional groups, 3-aminopropyltriethoxysilane (APTES) and phenyltrimethoxysilane, become strongly attached to the kaolin surface through Si–O–Si bonds and 3–6 nm sized Pd⁰ nanoparticles are uniformly decorated and stabilized through the organic amine moieties. The nano-palladium catalyst is durable, undergoing five times reuse with moderate catalytic activity. The XPS analysis of the catalyst before and after reaction suggested that the reaction might be performed via a catalytic cycle that begins with Pd⁰.