1,2,4-TRIAZOLES .22. DERIVATIVES OF S-TRIAZOLO[3,4-A]PHTHALAZINE AND RELATED RING SYSTEMS

Cyclization of 1-hydrazino-4-alkyl(aryl)phthalazines with aliphatic acids, ortho esters, cyanogen bromide, urea, or carbon disulfide gave the appropriate 3-substituted 6-alkyl(aryl)-s-triazolo[3,4-a]phthalazines in good yield. The tetracyclic bis-s-triazolo [3,4-a: 4,3-c] phthalazine system was readily available from 1,4-dihydrazinophthalazine, and the s-triazolo[4,3-b]-s-triazolo[3,4-a]phthalazine system was prepared by cyclization of 3-hydrazino-striazolo [3,4-a]phthalazine. Oxidation of s-triazolo [3,4-a]phthalazine gave s-triazole-3-carboxylic acid. The s-triazolo [3,4-a] phthalazine system was reduced by metal hydrides at the 5,6 position, but catalytic hydrogenation was unsuccessful. When treated with base, it underwent ring opening to 3-substituted 5-(2-cyanophenyl)- s-triazoles but was stable to hot mineral acid, whereas the bis-s-triazolo [3,4-a: 4,3-c] phthalazine system underwent ring opiening and subsequent hydrolysis to 6-hydrazino-s-triazolo [3,4-a] phthalazine with hot mineral acid. Alkylation of s-triazolo [3,4-a] phthalazine occurred exclusively at the 2 position under reflux conditions, whereas at room temperature alkylation occurred at both the 1 and 2 positions. Several electrophilic and nucleophilic reactions undergone by the nucleus are described, together with spectral characteristics of the fused system. © 1969, American Chemical Society. All rights reserved.