facile and rapid synthesis of 3,4- dihydropyrimidin-2-(1h)-ones and thione derivatives through the biginelli protocol using n-methylimidazolium acetate

Some protic ionic liquids (pils) were synthesized by the direct neutralization reaction of n-methylimidazole and 4-n,n-dimethylaminopyridine as nitrogen-containing heterocyclic organic bases with acetic acid and trifluoroacetic acid. the relative acidity of the prepared ionic liquids was evaluated by hammet acidity function using uv-vis spectroscopy. the catalytic effects of the obtained ionic liquids were investigated in the synthesis of 3,4-dihydropyrimidin-2-(1h)-ones and thione derivatives through biginelli reaction. among n-methylimidazolium acetate [mimh][oac], n-methylimidazolium trifluoroacetate [mimh][cf3co2], 4-n,n-dimethylaminopyridinium acetate [dmaph][oac] and 4-n,n-dimethylaminopyridinium trifluoroacetate [dmaph][cf3co2], [mimh][oac] provided the best results. using 5 mol% of [mimh][oac] as a catalyst, 3,4-dihydropyrimidin-2-(1h)-ones and thione derivatives were obtained in high to excellent yields at 100 ºc during 15-50 min.