An Efficient Catalytic Method for the Beckmann Rearrangement of Ketoximes to Lactams by Cyanuric Chloride and Phosphazene Catalysts

The Beckmann rearrangement of ketoximes to lactams was successfully achieved by a very small amount of cyanuric chloride and phosphazene by carrying out the reaction in a mixed solvent of trifluoroacetic acid and toluene under mild conditions. For instance, the Beckmann rearrangement of cyclohexanone oxime was completely performed under the influence of 0.5 mol % of cyanuric chloride (CNC) or phosphazene (1,3,5-triazo-2,4,6-triphosphorine-2,2,4,4,6,6-chloride: TAPC) in a 3:2 mixed solvent of trifluoroacetic acid and toluene at 70 °C for 4 h to give ϵ-caprolactam, which is an important monomer of 6-Nylon, in almost quantitative yield. The same strategy could be applied to laurolactam synthesis from cyclododecanone oxime.