Isomerism and lead(IV) acetate oxidation reactions of p-substituted phenylosazones of some substituted glyoxals and 1,2-diketones. Reactions of metallic acetates with nitrogen compounds. Part 5.

Abstract

The structures of the bis-(p-nitrophenyl)hydrazones and some bis-(p-bromophenyl)hydrazones of glyoxal, methylglyoxal, phenylglyoxal, butane-2,3-dione, benzil, and cyclohexane-1,2-dione were examined by i.r.,¹H n.m.r., and ¹³C n.m.r. spectroscopy. Generally the E,E forms of the osazones were obtained from direct synthesis except for the bis-(p-nitrophenyl) hydrazoneofcyclohexane-1,2-dione and phenylglyoxaland the bis-(p-bromophenyl)hydrazones of phenylglyoxal, which were obtained as the E,Z-chelate forms. Unstable yellow crystalline forms of the bis-(pnitrophenyl)hydrazones of glyoxal, butane-2,3-dione, and benzil containing two molecules of hexamethylphosphoramide (HMPA) of crystallisation, which may contain the E,Z-isomers, were isolated from HMPA solutions. Lead tetra-acetate oxidation of a range of E,E-osazones gave dehydrogenations to 1,2-bisazoethylenes. Similar oxidations of E,Z-osazones gave mainly 2-aryl-1,2,3-triazole type products (osotriazoles) along with lower yields of azoethylenes. Oxidation of cyclohexane-1,2-dione bis-(p-nitrophenyl)hydrazone gave a mixture of osotriazoles containing an acetoxy- or p-nitroacetanilido-group at the 3-position of the cyclohexyl ring.