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 SO 3 H‐functionalized ionic liquids, 3‐methyl‐1‐(4‐sulfonic acid)butylimi‐ dazolium hydrogen sulfate [MIM(CH 2 ) 4 SO 3 H][HSO 4 ] and 1‐(4‐sulfonic acid)butylpyridinium hydrogen sulfate [PY(CH 2 ) 4 SO 3 H][HSO 4 ], 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.