Objective:
A facile and efficient method for synthesis of 3, 4-dihydropyrimidin-2(1H)-ones via
Biginelli reaction catalyzed by a novel dicationic Brönsted acidic ionic liquid, [(EtNH2)2SO][HSO4]2, has
been successfully developed.
Material and Method::
3, 4-Dihydropyrimidin-2(1H)-ones were synthesized through one-pot
condensation of aromatic aldehydes, ethyl acetoacetate, and urea under solvent-free conditions using
[(EtNH2)2SO][HSO4]2
as a novel catalyst. The progress of the reaction was monitored by thin-layer
chromatography (ethyl acetate / n-hexane = 1 / 5). The products have been characterized by IR, 1H NMR,
13C NMR, and also by their melting points.
Results:
In this research, a library of dihydropyrimidinone derivatives was synthesized via Biginelli
reaction under solvent-free conditions at 120oC using [(EtNH2)2SO][HSO4]2
as a catalyst. Various aromatic
aldehydes, as well as heteroaromatic aldehydes, were employed, affording good to high yields of the
corresponding products and illustrating the substrate generality of the present method. In addition, the
prepared dicationic Brönsted acidic ionic liquid can be easily recovered and reused.
Conclusion:
1, 1’-Sulfinyldiethylammonium bis (hydrogen sulfate), as a novel dicationic ionic liquid, can
act as a highly efficient catalyst for the synthesis of 3, 4-dihydropyrimidin-2(1H)-ones under solvent-free
conditions.
Tuning the Biginelli reaction mechanism by the ionic liquid effect: the combined role of supported heteropolyacid derivatives and acidic strength