Kinetics and mechanism of reversible, base-catalyzed ring closure of 3-(methoxycarbonyl)propionanilide and O-(methoxycarbonylmethyl)-N-phenylcarbamate

Abstract

The rate constants of reversible, base-catalyzed ring closure of 3-(methoxycarbonyl)propionanilide (I) and O-(methoxycarbonylmethyl)-N-phenylcarbamate (II) to 1-phenyl-2,5-pyrrolidinedione (III) and 3-phenyl-2,4-oxazolidinedione (IV), respectively, and the rates of solvolyses of the cyclization products III and IV in water and methanol have been measured. In both cases, an equilibrium is established between the starting ester and the cyclization product in methoxide solutions which is strongly shifted in favour of the starting ester. In the case of ester II in methoxide solutions, the cyclization is followed by a much slower splitting of the cyclization product to give glycolic acid anilide. The effects of the group X = NH, CH2, O, S in the esters RNHCOXCH2.COOCH3 on the rates of the cyclization and solvolysis of the cyclization products is discussed.