Oxidation of bis-aroylhydrazones of 3,3-dimethylpentane-2,4-dione and thermal decomposition of the oxidation products

Oxidation of the title bis-aroylhydrazones 2 with lead tetraacetate gives l-aroyl-5-aroylazo-3, 4, 4, 5-tetramethyl-2-pyrazolines 6 in good yields. The aroylazopyrazolines 6 decompose by refluxing in chloroform or ethanol solution to l-aroyl-5-hydroxy-3, 4, 4, 5-tetramethyl-2-pyrazolines 3 , l-aroyl-5-methylene-3, 4, 4-trimethyl-2-pyrazoles 10 and 1-aroyl-3, 4, 4, 5-tetramethyl-2-pyrazolines 11 . The spectral data of the prepared compounds, as well as the reaction mechanisms are discussed.