Synthesis and Quantum Chemical Studies on the Tautomeric Structures of New Thiazole and Thiadiazine Derivatives

New series of thiazoles and thiadiazines incorporated with pyrazole ring were synthesized via the reaction of 2-(1-(4-cyano-1,5-diphenyl-1H-pyrazol-3-yl)ethylidene) hydrazine-carbothioamide or 4-imino-7-methyl- 2,3-diphenyl-2H-pyrazolo[3,4-d]pyridazine-5(4H)-carbothiohydrazide with different reagents. The structures of all tautomeric forms of the newly synthesized compounds were confirmed on the basis of spectral data aided with DFT and semi-empirical calculations.