Importance of acyl rearrangement in the acid-catalyzed reaction of ε-caprolactam with carboxylic acids

Reactions of Carboxylic, Phosphoric and Sulfonic Acids and their Derivatives

“…Scheme 12 experimental evidence, in this case, pointed to a B Ac 2 mechanism (Scheme 13), involving initial formation of anion (36), which either progressed stepwise to a tetrahedral intermediate (37) and thence, with expulsion of phenate, to the product (35) or formed product concertedly via transition state (38). 53 The pyridinolysis of S-methyl chlorothioformate, MeSC(O)Cl, showed a biphasic Brønsted-type plot, in agreement with a stepwise mechanism and a change in the rate-limiting step, from formation of a zwitterionic tetrahedral intermediate (T ± ) at high pK a to its breakdown at low pK a .…”