On the Microwave-Assisted Synthesis and Oxidation of Biginelli Compounds: Comparative Study of Dihydropyrimidinones and Thiones Oxidation

Title:On the Microwave-Assisted Synthesis and Oxidation of Biginelli Compounds: Comparative Study of Dihydropyrimidinones and Thiones Oxidation

Volume: 1 Issue: 2

Author(s): Marta Pineiro, Bruno F.O. Nascimento, Antonio M.d’A. Rocha Gonsalves, Sandra C.C. Nunes and Alberto A.C.C. Pais

Affiliation:

Keywords: 1, 4-dihydropyrimidine, 1, 4-dihydropyrimidinethiol, 3, 4-dihydropyrimidin-2(1H)-ones, 3, 4-dihydropyrimidine- 2(1H)-thiones, biginelli, dihydropyrimidines, electronic calculation, microwave, monastrol, oxidation, potassium peroxydisulfate, pyrimidin-2(1H)-ones, pyrimidine-2(1H)-thiones, synthesis, tautomers.

Abstract: A small library of twenty-two 3,4-dihydropyrimidin-2(1H)-ones and twenty-one thiones was synthesized under microwave irradiation using acetic acid as both solvent and catalyst. The oxidation of 3,4-dihydropyrimidin-2(1H)-ones to the corresponding pyrimidin-2(1H)-ones was systematically studied with heterogeneous and homogeneous oxidants. Microwave- assisted oxidation using potassium peroxydisulfate in an acetonitrile/water mixture at 100°C for 10 minutes produced the desired compounds in high yields for the majority of the 3,4-dihydropyrimidin-2(1H)-ones used. The decrease in the reaction yield observed in the case of 3,4-dihydropyrimidin-2(1H)-ones with bulky substituents at the C4 position was rationalized resorting to theoretical calculations. The oxidation of 3,4-dihydropyrimidine-2(1H)-thiones was also extensively studied. Using potassium peroxydisulfate or other powerful oxidants, such as oxone or hydrogen peroxide, pyrimidine-2(1H)-thione was not observed. However, evidence for the formation of this compound was obtained using 2,3-dichloro-5,6-dicyanobenzoquinone as oxidant under microwave irradiation. Electronic structure calculations indicate the stability of the 1,4-dihydropyrimidinethiol tautomer, which is deemed responsible for the different reactivity of these compounds.

Cite this article as:

Pineiro Marta, F.O. Nascimento Bruno, Rocha Gonsalves M.d’A. Antonio, Nunes C.C. Sandra and Pais A.C.C. Alberto, On the Microwave-Assisted Synthesis and Oxidation of Biginelli Compounds: Comparative Study of Dihydropyrimidinones and Thiones Oxidation, Current Microwave Chemistry 2014; 1 (2) . https://dx.doi.org/10.2174/2213335601666140422225203