Visible light thiocyanation of N-bearing aromatic and heteroaromatic compounds using Ag/TiO2 nanotube photocatalyst

Abstract

In this study, Ag/TiO₂ nanotubes (Ag/TNT) were synthesized via simple hydrothermal process, and this photocatalyst was successfully exploited in thiocyanation reactions at room temperature under visible light irradiation. Four classes of important heterocyclic compounds including indole, aniline, pyrrole and 2-amino thiazole derivatives via Ag/TNT treated with ammonium thiocyanate formed the corresponding thiocyano compounds in moderate to excellent yields. Plasmonic property and catalytic performance of Ag nanoparticles (which mainly deposited on the surface of TNT) in absorbing species containing sulfur atoms were key components for the reactions to proceed. This potent, simple and versatile protocol reported for the first time afforded thiocyanation reactions of aniline, pyrrole and 2-amino thiazole derivatives under visible light. The reactions proceeded through a radical pathway by applying air molecular oxygen as a low-cost and environmentally friendly terminal oxidant.