Green and Regioselective Alkylation of Dihydropyrimidinthiones through Michael Addition

Abstract

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.