Protic acidic ionic liquids: green, efficient and reusable catalyst for synthesis of dihydropyridines

In this methodology, at the beginning, environmentally friendly Protic acidic ionic liquids (HILs) have been synthesised by direct reaction of nitrogen heterocyclic compounds with various acids. Then, syntheis of dihydropyrimidines were investigated through one-pot, three-component reaction between substituted aromatic aldehydes, ethyl acetoacetate and urea (thiourea), using these green solvents at different temperature without any catalyst. The best results were afforded when [NImH]OAc was used at 100 oC for 5-10 min. It is worthwhile to mention that, the products were isolated and no further chromatographic purification was accomplished since no impurities were observed by NMR. Increasing the amount of catalyst, however, did not improve the yield significantly. Further investigation on the temperature effect indicated that high temperature did not reduce the reaction timeArvinnejhad

Keywords:

Dihydropyridines , protic ionic liquids , Green chemistry , multicomponent reactions