Intramolecular catalysis of phosphate triester hydrolysis. Nucleophilic catalysis by the neighbouring carboxyl group of the hydrolysis of dialkyl 2-carboxyphenyl phosphates

Abstract

The hydrolysis of dialkyl 2-carboxyphenyl phosphates is subject to highly efficient intramolecular catalysis by the carboxy-group. The anions are hydrolysed a few times faster than the acids but both ionic forms are hydrolysed some 10⁷ times faster than the corresponding compounds with no carboxy-group. The anions are hydrolysed to salicylic acid and the dialkyl phosphate, but the major products from hydrolysis of the acids are the monoalkyl 2-carboxyphenyl phosphates. Intramolecular nucleophilic catalysis appears to be involved in both cases. This behaviour, for the anion, is strikingly different from that of carboxylic esters of salicylic acid, and the explanation brings out an important quantitative difference between (carboxylic) acyl and phosphoryl transfer reactions.