Ionic Liquid, Surrogate Hydrogen Bromide Reagent for Ring Opening of Cyclopropyl Ketones

Ionic liquid reagents created by addition of 1 equiv of either CF₃CO₂H or CF₃SO₃H to N-pentylpyridinium bromide exhibit excellent chemical reactivities as surrogate HBr reagents in ring-opening reactions of cyclopropyl ketones as well as of 2,2-difluorocyclopropyl ketones to form the respective 3-bromopropyl or 3-bromo-2,2-difluoropropyl ketones in good to excellent yields.