Efficient conversion of carbon dioxide at atmospheric pressure to 2-oxazolidinones promoted by bifunctional Cu(ii)-substituted polyoxometalate-based ionic liquids

Abstract

Copper(II) substituted polyoxometalate-based ionic liquids e.g. [(ⁿC₇H₁₅)₄N]₆[α-SiW₁₁O₃₉Cu] were successfully developed as halogen-free bifunctional catalysts for the carboxylative cyclization of propargylic amines with CO₂. Such a CO₂ fixation protocol proceeded smoothly at atmospheric pressure under solvent-free conditions, in an environmentally benign and low energy-input manner. Notably, various propargylic amines could react smoothly to afford 2-oxazolidinones as the target products in high to quantitative yields. Furthermore, the dual activation of both propargylic amine and CO₂ by [(ⁿC₇H₁₅)₄N]₆[α-SiW₁₁O₃₉Cu] was studied using NMR techniques and control experiments.