The hydrogen bond basicityβof ionic liquids, as demonstrated by the NMR studies and the Kamlet–Taft linear solvation energy relationship, was confirmed to be the dominant solvent descriptor determining the rate of the Knoevenagel condensation.

Structurally diverse aromatic and aliphatic ionic liquids have been prepared via anion metathesis utilizing alkylammonium chlorides and trimethyl phosphate. Excellent oxygen-containing functional-group tolerance in preparation of potentially greener dimethyl phosphate ionic liquids has been demonstrated. For the first time, this method has been employed in the synthesis of dicationic imidazolium-based ionic liquids possessing a dimethyl phosphate counterion, providing a simple, direct route towards structurally novel products of high purity.

The melting points of DILs were determined by Stuart SMP3 apparatus. UV-VIS spectra were recorded on UV/VIS Spectrometer Lambda 25. High-resolution mass spectra were obtained with Agilent 6230 TOF LC/MS instrument. Negative-ion ESI-MS analysis was performed on Agilent 6230 TOF LC/MS mass spectrometer. ESI-MS spectra were obtained for the solutions (10 -3 M) of DILs in acetonitrile-water (1:1, v:v). 5 µL of the samples were injected directly into the spectrometer at a constant flow 5 µL/min. Source was used with the following parameters: negative ionization mode, drying gas flow 10 mL/min and 200 °C temperature, fragmentor ionization was set in a range of 0 to 130 V. N 2 was used as the sheath gas at flow 8 ml/min and 200 °C temperature. The mass scan range was from m/z 50 to 3000. Peak detection and spectrum extraction were performed with MassHunter Software (Agilent). Thermogravimetric analysis was performed by SII Extar6000 TG-DTA6300 under nitrogen atmosphere (temperature gradient 50…500 o C, heating rate -10 o C/min). The products of the Claisen rearrangement were identified by GC (Shimadzu GC-2010) using Restek Rtx®-1 Ms column (30 m x 0,25 mm x 0,25 µm) equipped with mass spectrometer (Shimadzu GC/MS-QP2010). Quantitative analysis of the reaction mixture was performed by GC (YL6100 GC) using the same column equipped with a flame ionization detector (FID). Helium was exploited as the carrier gas (flow rate -1 mL/min).

An unprecedented, convenient synthesis of a variety of 1,4‐dihydropyridine derivatives is described using ionic ligands possessing a (Me‐O)2PO2‐ counterion as promoter.