N,N,N′,N′-Tetramethylethylene-diaminium-N,N′-disulfonic acid trifluoroacetate and pyridinium-N-sulfonic acid hydrogen sulfate as highly effective dual-functional catalysts for the preparation of N,N′-alkylidene bisamides

In this research, Bronsted-acidic ionic liquids N,N,N',N'-tetramethylethylene-diaminium-N,N'-disulfonic acid trifluoroacetate ([TMEDSA][TFA](2)) and pyridinium-N-sulfonic acid hydrogen sulfate ([Py-SO3H] [HSO4]) have been introduced as dual-functional catalysts for the green, simple and effective preparation of N,N'-alkylidene bisamides by the reaction of primary amides (2 eq.) with arylaldehydes (1 eq.) under solvent-free conditions. The reaction results and conditions of the catalysts have been compared with the previously reported ones. [TMEDSA][TFA](2) and [Py-SO3H][HSO4] were superior to the previously reported catalysts in terms of two or more of these factors: reaction times (10-45 min), yields (86-98%), temperature and the reaction conditions. Additionally, a plausible and attractive mechanism based on dual functionality of the catalysts has been proposed.