HETEROCYCLIC COMPOUNDS FROM UREA DERIVATIVES .14. INTERACTION OF THIOCARBOHYDRAZIDE AND DIARYLCARBODI-IMIDES

Thiocarbohydrazide reacts with two molar proportions of diarylcarbodi-imides in dimethylformamide or methanol to yield 5-arylamino-4-(NN′-diarylguanidino)-3-mercapto-1,2,4-triazoles, together with some 4-aryl-3-aryl-amino-5-mercapto- and 4-aryl-3,5-di(arylamino)-1,2,4- triazoles. The structure of the main-products follows from the identity of their 3-S-alkylthio-derivatives with compounds synthesised unequivocally from equimolecular quantities of diarylcarbodi-imides and 3-alkylthio-4-amino-5- arylamino-1,2,4-triazoles. The structure of the latter is confirmed by the deamination of a selected member of this series to 3-anilino-5-methylthio-1,2,4- triazole. The 4-amino-3-arylamino-5-mercapto-1,2,4-triazoles required in this synthesis are accessible (side by side with their 4-aryl-3-hydrazino-5-mercapto- isomers) from 2-arylamino-1,3,4-thiadiazol-5-yl alkyl sulphones by the action of hydrazine which replaces the alkylsulphonyl moiety and effects the ring-conversion simultaneously. The ring-fission in this reaction may proceed by way of intermediates of the type H2N·NH·C(:NR) ·NH·NH·CS·SO2R; this mechanism is supported by the observation that interaction of 1,2-diamino-3-phenylguanidine and carbon disulphide gives the same two s-triazoles. 3-Alkylthio-5-arylamino-4- (NN′-diarylguanidino)-1,2,4-triazoles are further cyclised thermally, with loss of alkanethiol, to 7-aryl-3,6-di(arylamino)-s-triazolo[4,3-b]-s-triazoles.