Background: A facile, effective and green methodology has been developed for the synthesis
of 1,2-dihydropyridine-3,5-dicarbonitriles (3a-h) and ethyl 4H-pyran-2-carboxylates (5a-d) through
one-pot, two or three-component condensation reactions consisting of aromatic aldehydes, malononitrile
and cyanoacetic acid hydrazide or ethyl benzoylpyruvate in the presence of 1,4-diazabicyclo
[2.2.2]octane, DABCO, in aqueous ethanol at room temperature. This work consistently has
advantages as high yields, short reaction times, mild reaction condition, simple procedure and low
Methods: To a solution of arylaldehydes (1.0 mmol) and malononitrile (1.0 mmol) DABCO (20
mol%) H2O/EtOH (1:1, 10 mL) were added. The mixture was stirred for 15 min then cyanoacetic acid
hydrazide or ethyl benzoylpyruvate (1.0 mmol) was added to the mixture. The mixture was stirred at
ambient temperature for 90-120 min (the progress of the reaction being monitored by TLC and using
hexane/AcOEt 1:1 as an eluent). The resulting solid was filtered, washed with cold H2O for removal
of the catalyst, then crystallized from EtOH. All of the resulting structures were confirmed by their
physical constant, IR, 1H NMR, 13C NMR spectroscopy and elemental analyses.
Results: Convenient and practical protocols to 1,2-dihydropyridine-3,5-dicarbonitriles (3a-h) and 4Hpyran-
2-carboxylates (5a-d) from aromatic aldehydes, malononitrile and cyanoacetic acid hydrazide
or ethyl benzoylpyruvate using DABCO as an efficient catalyst are described.
Conclusion: In conclusion, we have presented DABCO as a mild and efficient catalyst for the synthesis
of the corresponding 1,2-dihydropyridine-3,5-dicarbonitriles (3a-h) and 4H-pyran-2-carboxylates
(5a-d). DABCO is inexpensive, nontoxic, easy to handle, and can act as a green medium. Simple
work-up procedure, short reaction times, excellent yields of product with better purity, green solvent
and mild condition are advantages of this protocol.