SYNTHESIS OF 2,4-THIAZOLIDINEDIONE-2-AZINES AND 2,4-THIAZOLIDINEDIONE-2-DIMETHYLHYDRAZONES FROM THIOCYANOESTERS AND HYDRAZINES

Thiocyanoesters were prepared from 2-bromoesters and potassium thiocyanate, and a series of substituted thiazolidinedione-2-azines was obtained from these thiocyanoesters using hydrazine hydrate. The structure of the thiazolidinedione-2-azines was determined by hydrolysis using hydrochloric acid in ethanol. The reaction of thiocyanoesters with dimethylhydrazine, generally speaking, was analogous to their reaction with hydrazine, but there were many differences. Only 1 mole of alcohol was eliminated rather than 2, and there was no apparent reaction for the ethyl 2-thiocyanononanoate and the methyl phenylthiocyanoacetate. Furthermore, the reaction of methyl 2-thiocyanoisobutyrate with dimethylhydrazine did not give a 2,4-thiazolidinedione-2-dimethylhydrazone but rather an addition product, N-dimethylamino-S-(1-methyl-1-carbomethoxy) ethylisothiourea. To illustrate the reactivity of the thiocyano group, benzyl thiocyanate was treated with hydrazine and the product was found to be dibenzyldisulphide, and ammonia was evolved. Similarly, trimethylene dithiocyanate gave the dimer of trimethylene disulphide. Finally, benzyl thiocyanate formed an addition product with dimethylhydrazine which was N-dimethylamino-S-benzylthiourea.