Synthesis of Condensed 1,2,4-Triazolo-Heterocycles

Cyclization of 2-hydrazino-1, 3-benzothiazole, 2-hydrozinoquioline, 2-hydrazinolepidine,
and 2-hydrazino-pyridine with one-carbon cyclizing agents such as triethyl orthoformate, ethyl chloroformate, urea, phenylthiourea, and carbon disulfide gave 3-substituted-1,2,4-triazolo (3,4, -b) 1, 3-benzothiazoles, 3-substituted-1,2,4-triazolo (4,3-a) quinolines, 3-substituted-1,2,4-triazolo (4,3-a) quinolines, 3-substituted-1,2,4-triazolo (4,3-a) lepidines and 3-substituted-1,2,4-triazolo (4,3-a) pyridines respectively. Reactions with acetic acid and acetic anhydride gave the corresponding acetyl hydrazines which were cyclized to the 3-methyl 1,2,4-triazolo-heterocyles. Ring closure with phenyl isocyanate and phenyl isothiocyanate, gave the intermediate 4-phenylsemicarbazides and 4-phenylthiosemicarbazides which, upon fusion, afforded the corresponding 3-oxo- and 3-thioxo-1,2,4-triazolo-heterocyles. The 3-oxo-compounds were also obtained when 2-chloroquinoloni or 2-chlorolepidine was fused with semicarbazide hydrochloride.