Aromatic Compounds Mannich Reaction Using Economical Acidic Ionic Liquids Based on Morpholinium Salts as Dual Solvent-Catalysts

Abstract

Economical acidic ionic liquids containing an alkanesulfonic acid group in a morpholinium cation were found to be effective catalysts for the Mannich reactions of various kinds of aromatic aldehydes, acetophenone and aromatic amines at mild reaction conditions. The satisfactory results were obtained with short reaction time, good yields of the Mannich bases and simplicity in the experimental procedure. These ionic liquids could be recycled and reused for up to five times without considerable decreasing in the catalytic activity.

Keywords:

• Catalysts
• economical ionic liquids
• Mannich reaction
• solvent-free conditions

ACKNOWLEDGMENTS

The author gratefully acknowledges SRTP of Anhui University of Technology (project no. 08028); the Key Project of the Scientific Research Foundation sponsored by the Education Department of Anhui Province, China (project no. KJ2010A339); and China Postdoctoral Science Foundation funded project (project no. 20100470153) for financial support.

Notes

Reaction condition: 10 mmol aromatic benzaldehyde, 10 mmol acetophenone and 10 mmol aromatic amine; temperature = 25 °C. Two drops of water (3.33 mmol) was added to the reaction mixtures.

^a Two drops of water was not added.

^b 15 mmol acetophenone and 15 mmol aniline was added to stir well.

^a 10 mmol benzaldehyde, 10 mmol aniline, and 10 mmol acetophenone, 2.5 mmol [MPA][TFA], temperature = 25 °C, time = 2 h.