Synthesis of New Thiazine and Thiazole Derivatives Via Cyclization Reactions; Investigating Their Electronic Properties and Determination of Antioxidant Properties

Abstract

(4-[2,4-dimethoxyphenyl]-6-phenyl-2-thioxo-1,2,3,4-tetrahydropyrimidin-5-yl)(phenyl) methanone (1) have been prepared by Biginelli three-component cyclocondensation reaction of catalyzed with p-toluene sulfonic acid in ethanol. Pyrimido[2,1-b]thiazine (2) and thiazolo[3,2-a]pyrimidine (3) derivatives were obtained by a simple one-pot condensation reaction of starting compound 1 and 3-bromopropionic acid, bromoacetic acid and, respectively. By performing the reactions of compound 3 with heteroaromatic and aromatic aldehydes, arylidine-bicyclic thiazolo pyrimidine compounds (4-9) were synthesized. Theoretical calculations and molecular electrostatic potential maps of all synthesized compounds were performed using the Gaussian software package Density Functional Theory (DFT/6-31G: B3LYP). In addition, studies were carried out to determine the antioxidant properties of all the compounds obtained by the DPPH method, and compound 1 was found to be the most effective compound. The structures of the newly synthesized compounds were analyzed using spectroscopic methods such as IR, H-1, and C-13.