The Preparation of 3-Phenyltriazolopyridines and Their Benzologs from N-(Phenylsulfonyl)benzohydrazonoyl Chloride and Pyridines

Article abstract of DOI:10.1246/bcsj.53.2007

3-Phenyl<1,2,4>triazolo<4,3-a>pyridines were obtained in good yields from N'-<α-(1-pyridinio)benzylidene>benzenesulfonohydrazidates, generated from 2-unsubstituted pyridines and N-(phenylsulfonyl)benzohydrazonoyl chloride (2), by oxidation with chloranil.The reaction of quinoline and isoquinoline with 2 gave 1-phenyl-3-phenylsulfonyl-3,3a-dihydro<1,2,4>triazolo<4,3-a>quinoline and 3-phenyl-1-phenylsulfonyl-1,10b-dihydro<1,2,4>triazolo<3,4-a>isoquinoline respectively, both in good yields; they aromatized to the corresponding triazoles by the 1,2-elimination of benzenesulfinic acid on heating.