Tautomerism and Reactions of 1H-1,2,4-Triazole-5-thiones with Hydrazonoyl Halides |
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Authors: | Mosselhi A N Mosselhi Magda A Abdallah Sayed M Riyadh Abdelhamid E Harhash Ahmad S Shawali |
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Abstract: | The acid dissociation constants (Ka) of a series of 3,4-diaryl-1H-1,2,4-triazole-5-thiones ( 1 ) were determined and were found to correlated linearly with Hammett substituent constants; log Ka = 1.06 σx ? 11.01. Such a result indicates that 1 exists essentially in one tautomeric form namely the thione form. Reactions of 1 with hydrazonoyl chlorides 2 gave the thiohydrazides 5 . Similiar reaction of 3-phenyl-1H(4H)- 1,2,4-triazole-5-thione 1g with 2a gave the thiohydrazide 5h which was converted into 1,3,5-triphenyl-1,2,4-triazolo3,4-c]-1,2,4-triazole ( 9 ). The latter was also prepared from 3-phenyl-5-methylthio-4H-1,2,4-triazole ( 6 ) and 2a . The mechanism of the reaction of 1 with 2 is discussed. |
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