syntheses, antibacterial and antifungal activities of substituted-thiazolo-1,3,4-thiadiazoles, 1,3,4-oxadiazoles and 1,2,4-thiazoles

starting from readily available 2-substituted-4-methylthiazole-5-carboxylic acid hydrazide (1), the title compounds were prepared. the reaction of compound 1 (r=ch3) with formic acid yielded 1-(formyl)-2-(2,4-dimethylthiazole-5-carboxyl) hydrazine (2). refluxing the latter with phosphorous pentasulfide in xylene afforded compound 3, the reaction of compound 2 with phosphorous pentoxide afforded compound 4. reaction of compound 1 with substituted isothiocyanates followed by cyclization of the intermediate 5 in basic medium gave 4-alkyl-5-(2-substituted-4-methyl-5-thiazolyl)-,4-dihydro-3h-1,2,4-triazole-3-thione (6). alkylation of compound 6 followed by subsequent oxidation of intermediate 7 gave compound 8. the reaction of acid chloride 11 with hydrazide 12 afforded compound 13 which was cyclized by p2s5 to compounds 14 or 15 respectively. compounds 3 and 14 showed significant activities against e. coli and bacillus subtilis.