An unexpected tandem cycloaddition reaction of α,β-unsaturated acid chloride with amines: Synthesis of dihydropyrancarboxamide derivatives and biological activity

Tandem cycloaddition reaction of α,β-unsaturated acid chloride with amines afforded in situ N-acylated amines, which undergoes cycloaddition reaction with other molecule of acid chloride to give dihydropyran carboxamide derivatives as an unexpected product. 2-Amino benzimidazole, 2-aminobenzthiazole, 2-aminothiazole, anthranilic acid, o-pheneylenediamine, and 3-methyl-1H-pyrazol-5(4H)-one are reacted with methacryloyl chloride at 0 °C to give different derivatives of dihydropyran carboxamide. The latter compound was obtained through acylation of the organic amines followed by tandem cycloaddition reaction. In contrast acryloyl chloride afforded only N-acylated derivatives. Both products are characterized by single crystal X-ray diffraction method. Bioactivity of the newly synthesized products was studied against Gram-positive, Gram-negative bacteria and fungus.