An efficient protocol for the preparation of pyridinium and imidazolium salts based on the Mitsunobu reaction

We report herein that, in the absence of any nucleophilic counterions, tertiary nitrogen nucleophiles such as pyridines and imidazoles can be alkylated with alcohols, by simply using their ammonium form as the acidic component of the Mitsunobu reaction. This led to efficient preparation of ionic liquids under mild conditions, avoiding the usual anion exchange step.