Organocatalyzed Beckmann rearrangement of cyclohexanone oxime by trifluoroacetic acid in aprotic solvent

The Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam catalyzed by trifluoroacetic acid in aprotic solvents such as toluene, 1,2-dichloroethane, acetonitrile, benzonitrile, nitromethane and their mixtures is described. High yield and selectivity in ε-caprolactam have been observed. Data relative to cyclohexanone oxime protonation equilibrium, interaction of ε-caprolactam with the acid, solvent effect on reaction kinetics and apparent activation energy are given together with some thoughts on the reaction mechanism.