A highly active Zn(salphen) catalyst for production of organic carbonates in a green CO2 medium

Zn(salphen), in combination with Bu4NI, was studied as a binary catalyst system for CO2-fixation in the context of organic carbonate formation. The catalytic potential of this binary catalyst system was considerably improved by working in a solvent-free, CO2-rich environment, thereby increasing the overall contact between the reagents and catalyst. Under these green conditions, excellent conversion and selectivity towards the cyclic carbonate product were obtained with epoxides that are generally less prone to undergo cycloaddition with carbon dioxide. The effect of the reaction conditions and the type of co-catalyst employed together with Zn(salphen) were systematically investigated and optimised.