Synthesis of N-alkylimidazolium salts and their utility as solvents in the Beckmann rearrangement

Six different room temperature ionic liquids (RTILs) based on N-methyl or N-isopropyl imidazolium cations with counteranions, such as BF4-, PF6-, and OTf−, have been synthesized by exchanging the counteranions of the corresponding N-methyl or N-isopropylimidazolium bromides using appropriate salts such as NH4BF4, KPF6, and AgOTf. Catalytic amounts of these ionic liquids (ILs) have been used as the reaction medium for the Beckmann rearrangement of oximes to amides in the presence of PCl5. A moderate to good conversion of oximes to amides in all the six ILs was observed.