Acidic task-specific ionic liquid as catalyst of microwave-assisted solvent-free Biginelli reaction

A simple and effective synthesis of 3,4-dihydropyrimidin-2(1H)-one and 3,4-dihydropyrimidine-2(1H)-thione derivatives has been developed on the basis of three-component condensation of substituted aromatic and heterocyclic aldehydes, methyl acetoacetate, and urea or thiourea in the presence of 10% of an acidic task-specific ionic liquid ([C4mim][HSO4]) as catalyst under microwave irradiation in the absence of a solvent. The proposed procedure ensures short reaction times (4.4–8 min) and good yields after purification by recrystallization.