Reactions of lead tetra-acetate with substituted benzaldehyde 5-phenyl-1,2,4-triazol-3-ylhydrazones

Abstract

In the reaction of lead tetra-acetate with substituted benzaldehyde 5-phenyl-1,2-4-triazol-3-ylhydrazones the presence of the triazole ring enhanced a cyclisation reaction leading to high yields of 3-aryl-6-phenyl-7H-s-triazolo-[4,3-b]-s-triazoles . Low yields of N-acetyl-N′-aroyl-N-(5-phenyl-1,2,4-triazol-3-yl) hydrazines were also isolated from a competitive acetoxylation reaction. The rates of the reaction were rapid, with second-order rate constants ca. 160–800 l mol^–1 s^–1 at 35° in glacial acetic acid. Substituents in the arylidene ring exerted a small influence (ρ=–0·60) on the reaction. The mechanism is discussed.