In this paper, we describe a new, simple and efficient strategy for the formation of novel and valuable acyl hydrazide derivatives from reaction between diverse acyl hydrazides and α,β-unsaturated esters in the presence of 1,4-diaza-bicyclo[2,2,2]octane (DABCO) -an inexpensive base -and tetrabutylammonium bromide (TBAB) -an ionic organic salt -under solvent-free conditions. In the reaction, double Michael adducts were produced in good yields in 7 h when acrylic esters were used as Michael acceptors. Surprisingly, no double Michael adducts were produced with fumaric esters, and single Michael adducts were the only products of these reactions in 10 h. ARTICLE HISTORY

INTRODUCTION: Dihydropyrimidines are one of the most important heterocyclic ring systems having a serious place in medicinal and organic synthesis METHOD: In this paper, a new series of dihydropyrimidines consisting of sulfur atoms were synthesized using inorganic base K2CO3 and TBAB as an organic salt to make high polarity in reaction media. Interestingly, different 3,4-dihydropyrimidin-2(1H)-thiones reacted smoothly with various acrylic esters to afford adducts via highly regioselective N3-Michael addition reaction was carried out at 100 oC in 12 h. Result: Unfortunately, the reaction failed with fumaric esters owing steric effects. Avoiding organic solvents during this reaction effectively led to the development of an economic approach. Conclusion: Structures of the new compounds were established on the basis of 1H NMR, 13C NMR, and IR spectral data.

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In this paper, a series of new dihydropyrimidinone derivatives using aza-Michael addition reaction were synthesized under solvent-free conditions. The reaction proceeded in the presence of K2CO3/TBAB, a media of inorganic base K2CO3 and organic ionic salt TBAB (tetrabutylammonium bromide) at 100 oC. The reaction of acrylic esters with dihydropyrimidinones produced N3-substituted derivative of dihydropyrimidinones with 85-95% yields in 6 h. But, fumaric esters did not have any response in the same reaction media even after 48 h at 100 oC. The reaction is characterized by high efficiency, relatively short reaction time, high yields, simple environmentally friendly reaction conditions.