An Efficient Synthesis of Pyrazolyl‐1,2,3‐thiadiazoles via Hurd–Mori Reaction

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An efficient synthetic strategy has been developed for the synthesis of pyrazolyl‐1,2,3‐thiadiazoles via Hurd–Mori cyclization reaction. The reaction of various pyrazolyl‐phenylethanones with semicarbazide hydrochloride in the presence of sodium acetate/methanol gave the corresponding semicarbazones (3a–i). These semicarbazones were further reacted with thionyl chloride via the Hurd–Mori cyclization conditions to accomplish the title products (4a–i). The present protocol favored for the formation of both pyrazolyl semicarbazone derivatives and pyrazolyl‐1,2,3‐thiadiazole derivatives by forming C─S, N─S, and C═N bonds in excellent yields with variety of substrates. The final compounds were characterized by analytical and spectral studies.