The halogen-free Brnsted acidic ionic liquid methylimidazolium hydrogen sulfate ([Hmim] + HSO 4 -) acts as a very efficient catalyst for the one-pot, two-component Baeyer condensation of a variety of aromatic aldehydes with dimethyl or diethyl aniline at room temperature. This green reagent behaves as both catalyst and solvent; that is, it exhibits dual-reagent catalysis. The room-temperature acidic ionic liquid could be recycled several times with almost no loss in the yield of the reaction. This is the first report of the Baeyer synthesis with a halogen-free ionic liquid. © 2012 Taylor and Francis Group, LLC.