Background: Mannich reaction is one of the most important carbon-carbon bond formation reactions
in organic synthesis. Traditional methods require a large amount of ungreen catalysts or much longer
reaction time, which limits the scope of their application. So, a recyclable catalyst with high activity
and selectivity is highly appreciated, and the highly shortened reaction time is also very appealing.
Methods: An efficient and facile process to prepare a series of β-amino carbonyl compounds was found via Mannich reactions
catalyzed by caprolactam-based Brønsted acidic ionic liquids under ultrasonic irradiation.
Results: [Capl][BF4] was the most effective catalyst in the Mannich reaction, and good yields was gained within 2-6 h.
The activity and stability of the catalyst was maintained very well even after five times, and ultrasound can effectively
shorten the reaction time and enhance the yield at ambient condition.
Conclusion: A convenient procedure for Mannich reaction using acidic ILs catalyst under ultrasonic irradiation has been
designed with many superiorities, such as simple manipulation, less reaction time and high yields. The Mannich reaction
takes place in no presence of organic solvents such as toluene or ethanol, etc. The new synthetic method reported in this
paper would make appreciable contribution to the subject of environmental friendly chemistry and it is available for industrial