Cyclo-condensation of substituted thiosemicarbazides: synthesis of 2,5- disubstituted 1,2,4-triazolidin- 3-thione

2-N-t-butylimino-3-γ-picolinoyl-5-arylimino-1,3,4-thiadiazoles (IVa-f) have been synthesized following the interaction of 1-γ-picolinoyl-4-aryl-3-thiosemicarbazides (IIIa-f) and t-butyl imino isocyanodichloride. The former (IIIa-f) in turn have been prepared by the condensation of aryl isothiocyanates (Ia-f) and isoniazide. The intermediate products (IVa-f) have been first isomerized into 2-γ-picolinoyl-4-N-t-butyl-5-arylimino-1,2,4-triazolidine-3-thiones (Va-f). The product (Va-f) have been successfully de-t-butylated into respective 2- γ-picolinoyl-5-arylimino-1,2,4-triazolidine-3-thiones (VIa-f). The structures of these compounds were established on the basis of elemental analysis and IR, PMR, Mass spectral data.