Abstract
A novel series of pyrazolyl 1,3,4-thiadiazines
⁻
,
⁻
,
,
⁻
,
⁻
, and
was prepared from the reaction of pyrazole-1-carbothiohydrazide
,
with 2-oxo-
'-arylpropanehydrazonoyl chloride, 2-chloro-2-(2-arylhydrazono)acetate, and 3-bromoacetylcoumarin. Moreover, the regioselective reaction of 5-pyrazolone-1-carbothiohydrazide
with 4-substituted diazonium salts and 4-(dimethylamino)benzaldehyde gave the corresponding hydrazones
⁻
and
. The newly prepared compounds were characterized by spectroscopy and elemental analysis. Many new synthesized compounds showed considerable antimicrobial activity against tested microorganisms. Hydrazones
⁻
and
showed remarkable antibacterial and antifungal activities. 4-(2-(
-tolyl)hydrazineylidene)-pyrazole-1-carbothiohydrazide
displayed the highest antibacterial and antifungal activities with minimum inhibitory concentration (MIC) values lower than standard drugs chloramphenicol and clotrimazole, in the range of 62.5⁻125 and 2.9⁻7.8 µg/mL, respectively.