Regioselective synthesis and antibacterial screening of new thiazol-2(3H)-imines linked to arene or chromene units

Abstract

A one-pot protocol was developed to prepare new thiazol-2(3H)-imines in efficient yields. Therefore, the reaction of the appropriate aromatic amine, phenyl isothiocyanate and chloroacetone (ratio 1:1:1) was mediated using different solvents and bases. The optimized protocol was to conduct the reaction in ethanol at reflux in the presence of 1.2 equivalents of sodium acetate. The reaction produced the regioisomeric (Z)-N-aryl-3-phenylthiazol-2(3H)-imine, as detected by 1D and 2D NMR spectral data. Using a similar protocol, new arene- or chromene-linked thiazol-2(3H)-imines were prepared by the use of the respective α-bromoketones. The new products were screened against six different bacterial strains. In general, chromene-linked thiazol-2(3H)-imines displayed superior antibacterial activity over other products. Thiazol-2(3H)-imines linked to 6-methyl and 6-methoxy-2-oxo-2H-chromene units had the most effective antibacterial activity with MIC/MBC values of 2.0/4.0 and 1.9/3.9 µM, respectively, against Staphylococcus aureus, Streptococcus mutans, and Escherichia coli strains.

Graphical Abstract

Keywords:

• Antibacterial activity
• chromene
• 2D NMR
• Hantzsch thiazole synthesis
• thiazol-2(3H)-imines