A highly efficient and sustainable catalyst system for terminal epoxy-carboxylic acid ring opening reactions

The nucleophilic ring opening of epoxides by carboxylic acids is an indispensable transformation for materials science and coating technologies. Due to this industrial significance, improvements in operational energy consumption and catalyst sustainability are highly desirable for this transformation. Herein, an efficient, environmentally benign and non-toxic halide free cooperative catalyst system based on an iron(III) benzoate complex and guanidinium carbonate is reported. The novel catalyst system shows improved activity over onium halide catalysts under neat conditions and in several solvents, including anisole and ⁿBuOAc. Detailed mechanistic studies using FeCl₃/DMAP as a catalyst revealed the importance of a carboxylate bridged cationic trinuclear μ₃-oxo iron cluster and guanidinium carbonate or DMAP as a carboxylate reservoir due to its superior activity.