Abstract: | Methylglyoxalyl chloride arylhydrazones (III) react with an ethanolic solution of thiourea to give 2-amino-4-methyl-5-arylazothiazoles (XII) instead of the expected 2-acetyl-4-aryl-5-imino-Δ2-1,3,4-thiadiazolines (V) which were obtained from III and potassium thiocyanate. 3-Thiocyanato-2,4-pentanedione (IV) coupled with diazotized anilines to give V. The postulated routes to formation of V and XII from III are given. Nitrosation of V gave the corresponding N-nitroso derivatives (VI) which decomposed upon refluxing in dry xylene to give 2,4-disubstituted-Δ2-1,3,4-thiadiazolin-5-ones (VII). Boiling of either V or VI with hydrochloric acid gave the hydrochloride salt (VIII). The thiadiazolines V gave the respective N-acyl derivatives (IX) and (X) with acetic anhydride and benzoyl chloride in pyridine. |