R. Iqbal et al., SYNTHESIS OF SOME NEW 2-(4-HALOPHENYLAMINO)-5-(ISOMERIC PYRIDYL)-1,3,4-THIADIAZOLES, Journal of the Chemical Society of Pakistan, 19(1), 1997, pp. 77-82
Twelve 2-(4-halophenylamino)-5-(isomeric pyridyl)-1,3,4-thiadizoles (1
7-28) were prepared as pure crystalline solids, by the acid catalysed
intramolecular dehydrative cyclization of the corresponding 4-(4-halop
henyl)-1-(isomeric pyridoyl) thiosemicarbazides (5-16). The latter wer
e prepared by reaction of 4-halophenyl isothiocyanate (3a-d) with each
of the three isomeric pyridinecarboxylic acid hydrazides (4a-c). The
effect of structure on reactivity with respect to the halogen atom and
isomeric pyridyl group is discussed. A plausible mechanism for intram
olecular cyclodehydration of the thiosemicarbazides to 1,2,4-thiadiazo
les is also suggested. The purified new compound, were characterized o
n the basis of elemental analysis, IR and mass spectral data.