Bronsted acidic ionic liquid: An efficient and reusable catalyst for the synthesis of 3,4-dihydropyrimidin-2(1H )-ones

A novel ionic liquid, 3-carboxymethyl-1-methylimidazolium bisulfate (CMImHSO(4)), was synthesized and used as a recyclable catalyst for the Biginelli reaction under solvent-free conditions. High yields of various substituted 3,4-dihydropyrimidin-2(1H)-ones (or thiones) were obtained. The ionic liquid can be recovered and recycled easily without loss of activity.