Catalysis of Sulfonate Ester Hydrolysis by Intramolecular Amide Group Assistance.

Article abstract of DOI:10.1021/jo00218a019

Kinetics of the alkaline hydrolysis of aryl 2-(acylamino)benzenesulfonates (1, X=OAr) obey the equation k_obs=(K_a+k_b->/(1++>/K_o).Hammett equations correlate the parameters k_a, k_b, and K_a for variation in both amido and leaving phenolate substituents.The values and sign of the ρ values together with entropy of activation data, reactivity trapping, and oxygen-18 incorporation are consistent with the formation of an intermediate benzoxathiazine S,S-dioxide (2).The k_a term involves intramolecular attack of the amido anion.The k_b term is consistent with a specific anion effect on k_a.Regular bimolecular B_Ac2 mechanisms for k_a and k_b are not consistent with the high observed reactivity of these parameters.