Beckmann Rearrangement. Ionic Liquid Research

In this dissertation Beckmann rearrangement of ketoxime in acidic ionic liquids was studied. Beckmann rearrangement of acetophenone oxime in acidic ionic liquid [Hmim]HSO₄ was achieved without the presence of any other catalyst. Under optimized conditions (120℃for 6h), 54.2% conversion of the substrate and 52.7% yield of the product were obtained. If P₂O₅ was added as a catalyst, the conversion of the substrate and the yield of the product increased to 98.9% and 98.5% respectively. When the reaction was carried out at 90℃for 6h with 6:5:1 ratio of [Hmim]HSO₄, acetophenone oxime and P₂O₅. Effects of other catalysts, including ZnCl₂, AlCl₃, PCol₃, etc, on the reaction were also examined, and results show that PCl₃ was the best catalyst for the reaction. The ionic liquid can be recovered through simple distillation and reused in the reaction. The optimized condition was then expanded to Beckmann rearrangement of other oximes including aromatic ketoximes, cyclic aliphatic ketoxime and open chain aliphatic ketoxime. It was found that the reactivity of the oximes according to the following order: aromatic ketoxime> cyclic aliphatic ketoxime > open chain aliphatic ketoxime.Beckmann rearrangement of acetophenone oxime and other ketoxime in more acidic ionic liquid [TEBSA]HSO₄ was also studied. Under optimized conditions(120℃for 2h), 89.6% conversion of the substrate and 85.1% yield of the product were obtained without the presence of any catalysts. This results show that ionic liquids with a sulfonic group such as [TEBSA]HSO₄ is a powerful solvent for Beckmann rearrangement of ketoxime. In the literature, we did not found any example of carrying out Beckmann rearrangement in ionic liquids without the presence of any other catalysts.