Heterocyclic Synthesis with 4-Benzoyl-1-cyanoacetylthiosemicarbazide: Selective Synthesis of Some Thiazole,Triazole, Thiadiazine,Pyrrylthiazole, and Pyrazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]triazine Derivatives

Summary. 4-Benzoyl-1-cyanoacetylthiosemicarbazide undergoes coupling reaction with aromatic diazonium chloride to afford (arylhydrazono)thiosemicarbazide, which was reacted with phenacyl bromide regioselectivity to afford the thiazoline. The (arylhydrazono)thiosemicarbazide could be transformed into the pyrazolo[1,5-a]triazine. Heterocyclization of 4-benzoyl-1-cyanoacetylthiosemicarbazide with α-haloketones (bromoacetone and phenacyl bromide), ethyl iodide, and ethyl bromoacetate furnished the pyrrylthiazoles, 1,2,4- triazole, and 1,3,4-thiadiazine. The latter was coupled with aromatic diazonium chloride to give the bis(arylhydrazono)‐thiadiazine. The mechanism for the formation of the title compounds was suggested and discussed.     

Regioselective Synthesis of Some New Pyrazolo[1,5‐a]pyrimidines,Pyrazolo[1,5‐a]quinazoline and Pyrimido[4′,5′:3,4]pyrazolo[1,5‐a] pyrimidines Containing Thiazole Moiety

A regioselective synthesis of novel pyrazolo[1,5‐a]pyrimidines, pyrazolo[1,5‐a]quinazoline and pyrimido[4′,5′:3,4]pyrazolo[1,5‐a]pyrimidines incorporating a thiazole moiety was described via the reactions of the versatile, readily accessible 5‐amino‐3‐(phenylamino)‐N‐(4‐phenylthiazol‐2‐yl)‐1H‐pyrazole‐4‐carboxamide 3 with appropriate 1,3‐biselectrophilic reagents namely, β‐diketones, enaminones, and α,β‐unsaturated cyclic ketone. The newly synthesized compounds were elucidated by elemental analysis, spectral data, and alternative synthetic route whenever possible.