Catalytic etherification of glycerol with short chain alkyl alcohols in the presence of Lewis acids

Abstract

Here we report the homogeneously-catalyzed etherification of glycerol with short chain alkyl alcohols. Among the large variety of Brønsted and Lewis acids tested, we show here that metal triflates are not only the most active but are also capable of catalyzing this reaction with an unprecedented selectivity. In particular, in the presence of Bi(OTf)₃, the targeted monoalkylglyceryl ethers were obtained with up to 70% yield. Although tested Brønsted acids were also capable of catalyzing the etherification of glycerol with alkyl alcohols, they were found however less active and less selective than Bi(OTf)₃. By means of counter experiments, we highlighted that the high activity and selectivity of Bi(OTf)₃ may rely on a synergistic effect between Bi(OTf)₃ and triflic acid, a Brønsted acid that can be released by in situ glycerolysis of Bi(OTf)₃. The scope of this methodology was also extended to other polyols and, in all cases, the monoalkylpolyol ethers were conveniently obtained with fair to good yields.