Brønsted acid-surfactant-combined catalyst for the Mannich reaction in water

A series of Brønsted acid-surfactant-combined catalysts (BASCs) functionalised with different acids have been synthesized and applied to catalyze the three-component Mannich reaction with aldehyde, acetone and amine at 25 °C in water. The effects of cation tail length and ions of the ionic liquid and the recyclability of the catalysts and BASC acidity (H0) were investigated. The results demonstrated that the 3-(N,N-dimethyloctylammonium) propanesulfonic acid toluene sulfate ([DOPA][Tos]) provide the best catalytic activity because of the formation of emulsions during the reaction. The catalytic procedure was simple and the catalyst could be recycled 9 times by simple separating processes without noticeably decreasing the catalytic activity.