Oxidation of aromatic compounds: VII. Oxidation of symmetrically substituted 1,3-diarylpropynones in the system CF3COOH-CH2Cl2-PbO2. New synthesis method of 1,1,2,2-tetraaroylethenes

Preparative oxidation of 1,3-diarypropynones ArC=CCOAr in a system CF3COOH- CH2Cl2-PbO2 at 18-20 degreesC within 1.5-25 h results in 1,1,2,2-tetraaroyl ethenes (ArCO)(2)C= C(COAr)(2) in yields up to 75%. The most easily and eff iciently the products form from the substrates where the aryl moiety conjug ated with the triple bond contains electron-donating substituents p-MeO, p- Me, and p-t-Bu. On heating with hydrazine 1,1,2,2-tetrakis(4-methoxyphenylc arbonyl)ethene is converted into heterocyclic structures: pyridazine and 2, 3,6,7-tetraazanaphthalene derivatives.