Preparation of glycerol monoester using triphenylphosphine and halogenating reagents

Abstract

The preparation of glycerol monoester by esterification of carboxylic acids with 1,2-O-isopropylideneglycerol using triphenylphosphine and halogenating agents was studied. The effects of type of halogenating agents, amount of reagents, amount of PPh3, amount of 1,2-O-isopropylideneglycerol, solvent system and reaction time were investigated to optimize the reaction conditions. Ethyl trichloroacetate as a combination with triphenylphosphine was a good reagent for the preparation of (2,2-dimethyl-1,3-dioxolan-4-yl)methyl benzoate from benzoic acid and 1,2-O-isopropylideneglycerol in dichloromethane at reflux temperature within 5 hours, the product yield is 84%. This reaction worked well for all selected carboxylic acids: i.e. saturated carboxylic acid, unsaturated carboxylic acid and aromatic carboxylic acid. The deprotection of (2,2-dimethyl-1,3-dioxolan-4-yl)methyl benzoate using hydrochloric acid to transform to 2,3-dihydroxypropyl-1-benzoate was accomplished, the product yield is 94%. This new methodology to prepare the glycerol monoester gave high product yield under mild and acid free condition.