Efficient synthesis of Mannich bases by sonication in sodium dodecyl sulfate micellar media

Water is a desirable solvent for synthesis because water is cheap, safe and non-toxic. However, the use of water as solvent is limited to water-soluble compounds, thus excluding most organic, lipophilic substances. A solution to this issue is to increase the solubility of organic compounds by using a surfactant to form micelles and, in turn, increase contacts with the reagent. Here, we tested ultrasound irradiation and sodium dodecyl sulfate micellar media on Mannich reaction of aldehydes, aromatic amines and acetophenone derivatives or cyclohexanone. The sonication of biphasic systems was performed at 37 kHz, 300 Watt, under neutral conditions. Results show that the reaction is carried out readily under milder conditions. The precipitated solid Mannich product was recovered by a simple filtration without using any organic solvent. This method provides advantages such as short reaction time, mild reaction conditions and simple work-up.