Synthesis, spectroscopic characterization, X-ray structures, DFT calculations, and molecular docking studies of novel (<i>Z</i>)-2 and 4-methoxy-<i>N</i>-(4-oxo-1,3-thiazinane-2-ylidene)benzenaminium bromide

Two novel isomers (<i>Z</i>)-2-methoxy-<i>N</i>-(4-oxo-1,3-thiazinane-2-ylidene) benzenaminium bromide (<b>1a</b>) and (<i>Z</i>)-4-methoxy-<i>N</i>-(4-oxo-1,3-thiazinane-2-ylidene)benzenaminium bromide (<b>1b</b>) of 1-3-thiazinane skeleton benzenaminium bromide salts have been synthesized from the reaction of 3-bromopropinoylisothiocyanate with acetone solutions of 2 and 4-methoxyaniline, respectively for 4 hours at 60°C. The nucleophilic attack of the thiono groups with the presence of the bromine atom at the beta position of the alkyl chains allows the cyclization reaction to occur, resulting in unexpected products. <b>1a</b> and <b>1b</b> were characterized using the FT-IR, ¹H, and ¹³C NMR spectroscopic techniques. X-ray crystallographic studies showed that <b>1a</b> crystallized in a triclinic crystal system with space group Pī, while <b>1b</b> crystallized in a monoclinic crystal system with space group P21/c. The asymmetric unit of <b>1a</b> consists of two crystallographically independent molecules, while only one molecule is in the asymmetric unit for the <b>1b</b> compound. The geometrical parameters of <b>1a</b> and <b>1b</b> are relatively well produced by DFT calculations. Finally, the compounds anti-coronas SARS-CoV2 against the main protease have been investigated by estimating their binding affinities into the main protease binding site. The two compounds were found to fit well into the binding affinity, which may suggest the high binding affinities of <b>1a</b> and <b>1b</b> compounds towards the main protease anti-coronavirus SARS-CoV2.