Nucleophilic Catalysis of Hydrolysis of a Schiff Base by Amines. Intramolecular Catalysis of Transimination

Article abstract of DOI:10.1021/jo00359a025

Certain groups of amines were found to catalyze hydrolysis of N-(o-methoxybenzylidene)-2-methoxyethylamine through transimination.The rate-determining transimination was followed by rapid hydrolysis of an intermediate Schiff base.Rate constants for the transimination with simple, but less basic, amines change sigmoidally with pH and are buffer-dependent in accord with a mechanism involving a trapping of the incipient tetrahedral intermediate T⁺₁ by a proton transfer to acids or bases.Morpholine behaved similarly.In the reaction with bifunctional amines carrying an internal amino group, rates are independent of both pH and buffer concentrations.Initial nucleophilic attack of these amines is rate determining in the whole pH range examined because of the rapid trapping of T⁺₁ by an intramolecular proton transfer.