One-pot catalytic conversion of carbohydrates into alkyl lactates with Lewis acids in alcohols

With the wide application of lactic acid/alkyl lactates in food, cosmetic, chemical, and biodegradable plastic, much attention has been paid to efficiently convert carbohydrates to lactic acid/alkyl lactates. In this study, an efficient and one-pot Lewis acid-catalyzed conversion of carbohydrates to alkyl lactate in alcohols was proposed. Zn(II) gave the highest yield of ethyl lactates, 47.7% for glucose, 51.7% for fructose and 47.5% for sucrose, respectively, which are the best yields so far. The presence of a small amount of water (about 3%) improved the yield of alkyl lactate and the counter anion had a great effect on the yields of alkyl lactates. According to the intermediates detected and the coordination of Zn(II) with various substrates proved by infrared spectroscopy, the reaction mechanism was proposed and the activation energies were calculated step by step.