Thiourea In The Ionic Liquid Of The Reaction And Biginelli Condensation Reaction

The synthesis of cinnamoyl thiourea derivatives from cinnamoyl isothiocyanate (CIT) with substituted aniline (RC₆H₄NH₂) was investigated in ionic liquid l-butyl-3-methylimidazolium tetra-fluoroborate, [Bmim]BF₄ at room temperature. The effects of reation time and molar ratio of reactants on the synthesis of cinnamoyl thioureas were tesetd. Comparison of the reaction times and yields in organic solvent (CH₂Cl₂ as solvent, PEG-600 as phase transfer catalyst) with those in ionic liquid suggested that [Bmim]BF4 was an excellent solvent and catalyst. Significant enhancements in reactivity, yield and reaction rate were achived in this method. The products could be recovered by simple filtraton. [Bmim]BF4 could be recycled simply by moving water under vacuum and reused at least 9 times without any loss of activity.Three-component Biginelli condensation was investigated in 1-butyl-3-methylimidazolium hexa-fluorophosphate, [Bmim]PF6 at room temperature. The condensation of benzaldehyde (10 mmol), ethyl acetoacetate (10 mmol) and urea (10 mmol) catalyzed by 2 g [Bmim]PF₆ (wth 3 drops of concentrated HCl) under solventless condition could proceed within 4 h in 60.0% yields. The reaction catalyzed by [Bmim]PF₆ with catalytic concentrated HCl in absolute ethanol could proceed smoothly within 17 h with high yields. Many advantages including simple operation, easy separation and purification of the products, mild reaction condition were achieved in this method. Ionic liquid coud be reused for many times.