DBU-MIm coupled ionic liquids as reusable catalysts for the Biginelli reaction

In present work, the application of a novel set of 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) and methylimidazole (MIm) coupled ionic liquids (ILs) in the Biginelli reaction has been investigated. In the modified Biginelli reaction, cinnamaldehyde, urea, and 1,3-diketone condensed in the presence of 10 mol% of the DBU-MIm coupled IL catalyst at 90 °C to afford dihydropyrimidinones in high to excellent yields in 45 min. Additionally, the effect of temperature, catalytic amount, and solvent has also been unfolded. The reaction has been found to the follow iminium ion mechanism and the synergic role played by the [DBUH]+ and [MIm]− moieties has been established by DFT calculations. The easy post-procedure recovery and reusability of the DBU-MIm IL catalysts make the present protocol of Biginelli synthesis simple, benign and reproducible.