A series of 3,4-dihydropyrimidin-2(1H)-ones were prepared through the Biginelli condensation reactions of aromatic aldehydes, keto ester and urea catalyzed by Brönsted acidic ionic liquid 3-methyl-1-(3-sulfopropyl)-imidazolium trifluoroacetate under solvent free conditions. The method is simple, solvent free, high yields and environmental friendly. The catalyst could be recycled and reused. The reactions were carried out in boiling water bath for 30~40 min. The yields of the products were between 81%~94%. All the products have been characterized by 1 H NMR and IR spectra.
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