Silica-supported silver nanoparticles as an efficient catalyst for aromatic C–H alkylation and fluoroalkylation

Abstract

The efficient catalysis of oxidative alkylation and fluoroalkylation of aromatic C–H bonds is of paramount importance in the pharmaceutical and agrochemical industries, and requires the development of convenient Ag⁰-based nano-architectures with high catalytic activity and recyclability. We prepared Ag-doped silica nanoparticles (Ag^0/+@SiO₂) with a specific nano-architecture, where ultra-small sized silver cores are immersed in silica spheres, 40 nm in size. The nano-architecture provides an efficient electrochemical oxidation of Ag⁺@SiO₂ without any external oxidant. In turn, Ag⁺@SiO₂ 5 mol% results in 100% conversion of arenes into their alkylated and fluoroalkylated derivatives in a single step at room temperature under nanoheterogeneous electrochemical conditions. Negligible oxidative leaching of silver from Ag^0/+@SiO₂ is recorded during the catalytic coupling of arenes with acetic, difluoroacetic and trifluoroacetic acids, which enables the good recyclability of the catalytic function of the Ag^0/+@SiO₂ nanostructure. The catalyst can be easily separated from the reaction mixture and reused a minimum of five times upon electrochemical regeneration. The use of the developed Ag⁰@SiO₂ nano-architecture as a heterogeneous catalyst facilitates aromatic C–H bond substitution by alkyl and fluoroalkyl groups, which are privileged structural motifs in pharmaceuticals and agrochemicals.