Novel One-Step Synthesis Process from Cyclohexanone to Caprolactam in Trifluoroacetic Acid

This paper presents a novel direct conversion of cyclohexanone to caprolactam catalyzed by trifluoroacetic acid. High conversion of cyclohexanone (100%) and high selectivity to caprolactam (above 99%) have been observed using acetonitrile as the additive. In addition, the effects of solvent, temperature, and catalyst composition on the reaction rate and selectivity to caprolactam were investigated. It is found that water could greatly decrease the reaction rate, whereas HCl could increase the reaction rate. On the basis of the results, the possible reaction route has been provided. This is the first example of an organocatalyzed one-step transformation of ketoxime into the corresponding amide, which may lead to the synthesis of caprolactam via a shorter and more environmentally friendly route.