SO3H-Functionalized Ionic Liquids: Green, Efficient and Reusable Catalysts for the Facile Dehydration of Aldoximes into Nitriles

Easily synthesized aldoximes have been converted to the corresponding nitriles under very mild conditions by a simple reaction using two halogen-free SO3H-functionalized ionic liquids, 3-methyl-1-(4-sulfonic acid)butylimidazolium hydrogen sulfate [MIM(CH2)(4)SO3H][HSO4] and 1-(4-sulfonic acid) butylpyridinium hydrogen sulfate [PY(CH2)(4)SO3H][HSO4], as catalyst and reaction medium without any additional organic solvent. The method was equally effective for aromatic aldoximes bearing electron-donating and electron-withdrawing substituents. Taking into account environmental and economical consideration, the protocol presented here has the merits of environmentally friendly, simple operation, easy work-up and very good yields. The catalysts could be recycled and reused for several times without noticeably decreasing in their catalytic activities.