Remarkable improvement of epoxide ring-opening reaction efficiency and selectivity with water as a green regulator

Abstract

Glycidyl esters are synthesized through the epoxide ring-opening reactions, and the reaction efficiency must be greatly improved for green and efficient production. In this work, the structure of the side product that caused the decline of selectivity was confirmed by GC-MS and ¹H NMR. The formation mechanism of the side product was unraveled, indicating that the relative rates of the parallel competing reactions towards the conversion of an intermediate was a key factor in selectivity. It was found that water as a proton transfer carrier can effectively facilitate the conversion of the intermediate to the target product, thus successfully suppressing the side reactions. The water content of 8–10 wt% in the reaction system was proved to be the optimized range. Relying on the function of water, the ring-opening reaction can be performed at 100 °C instead of 70 °C, and epichlorohydrin (ECH) could be directly fed in the reaction system once instead of dripping for 1 hour. Thus, the reaction time could be reduced from 6 hours to 1 hour, and the product selectivity could be maintained higher than 98%. The industrial production process further proved the effectiveness of this strategy in terms of broadening the temperature range for the highly selective synthesis of glycidyl esters and reducing the scale-up effect.