Reagents and Synthetic Methods 15. Phenyl Dichlorophos-Phate-Dimethylfurmamide Complex. A Modified One-Pot Procedure for Esterification of Carboxylic Acids

The most frequently used reagents for the one-pot conversion of carboxylic acids into esters have recently reviewed1. A considerable number of organophosphorus compounds have been used extensively as coupling agents. H-J. Liu et al2 described a reagent phenyl dichlorophosphate to activate the carboxy group for synthesis of esters. During our studies directed towards ester synthesis, we became interested in this reagent. We have found that this reagent reacts rapidly with car boxylic acids in the presence of organic tertiary base but the possible intermediate mixed anhydride 5 undergoes a rapid disproportion such as in the case of the phthaloylglycine and 3,5-dinitrobenzoic acid.