Kinetics and mechanism of hydroxy compound cinnamoylation in acetonitrile catalyzed by N-methylimidazole and 4-dimethylaminopyridine.

The kinetics of reaction of the acylating agents trans-cinnamic anhydride and trans-cinnamoyl chloride with the hydroxy compounds n-propyl alcohol and water in the presence of N-methylimidazole and 4-dimethylaminopyridine were studied spectrophotometrically in acetonitrile solution at 25 degrees. The acid chloride reacted via the intermediate formation of the N-acyl catalyst, which underwent general base-catalyzed reaction with the hydroxy compound. The anhydride did not form the N-acyl intermediate, but instead underwent direct general base catalysis. In the presence of water, all systems formed the N-acyl intermediate. The mechanistic route followed by the system was determined by the nucleophilicity of the catalyst, the ability of the leaving group, and the polarity of the solvent.