Under mild conditions and without any additional organic solvents, Beckmann rearrangement of ketoximes was performed in a novel task-specific ionic liquid consisting sulfonyl chloride. Especially for the conversion of cyclohexanone oxime to e-caprolactam, e-caprolactam has good solubility in water while the task-specific ionic liquid is immiscible with water, therefore, e-caprolactam could be easily separated from the reaction system by water extraction.

★★★★☆ J. Gui et al. / Tetrahedron Letters 45 (2004) 2681–2683.