Antioxidant properties of amide derivatives of 3,4-dihydropyrimidin-2-one with phenolic substituent in heterocycle

Abstract

The antioxidant properties of 4-[3,5-di(tert-butyl)-4-hydroxyphenyl]-5-aminocarbonyl-6-methyl-3,4-dihydropyrimidin-2-one were researched by volumetric analysis and decomposition of hydroperoxide. The reactant was obtained by three-component Biginelli condensation using urea, 3,5-di (tert-butyl) -4-hydroxybenzaldehyde and acetoacetic acid amide as reactants. The decomposition of cumene hydroperoxide in dimethylformamide under these conditions is described by a first-order kinetics equation. As the concentration of hydroperoxide increases, the rate of its decomposition decreases, apparently due to the formation of dimethylformamide dimer stabilized by molecules. 4- [3,5-Di (tert-butyl) -4-hydroxyphenyl] -5-aminocarbonyl-6-methyl-3,4-dihydropyrimidin-2-one inhibits the decomposition of hydroperoxide by slowing induced and homolytic cleavage. The inhibitory effect rises with the increase of the concentration of the inhibitor. An equation, which describes the inhibitory action of the analyzed compound on the hydroperoxide decomposition, was proposed, and the coefficients of this equation were calculated. The initiated oxidation of cumene was carried out at a temperature of 343 K in the presence of the initiator azodiisobutyronitrile. The concentration of 4- [3,5-di (tert-butyl) -4-hydroxyphenyl] -5-aminocarbonyl-6-methyl-3,4-dihydropyrimidin-2-one varied from 1,5×10-4 до 5,0×10-3 mol / l. In the concentration interval of the analyzed substance (1,25¸5,0)×10-3 mol / l the duration of the induction period exceeds 60 min. At lower concentrations, a linear change in the duration of the induction period is observed. The inhibitory action of 4- [3,5-di (tert-butyl) -4-hydroxyphenyl] -5-aminocarbonyl-6-methyl-3,4-dihydropyrimidin-2-one is higher than that of ionol. The basic kinetic parameters of the processes of initiated oxidation of cumene and decomposition of cumene hydroperoxide are calculated. Therefore, the analyzed compound has an antioxidant effect both during the decomposition of hydroperoxide and during the initiation of cumene oxidation. The phenolic group and the urea moiety of the dihydropyrimidinone cycle have an inhibitory effect.