Overcrowded molecules. V. 3,10-dimethyl-1,12-bis(2-pyridyl)benzo[c] phenanthrene-2,11-diol

The bis ketene acetal adduct of 4a,10a-diazoniaanthra[1,2-α]anthracene diperchlorate ( 10 ) was used to prepare the highly overcrowded benzo[c]phenanthrene 2 by a known procedure. Its oxidation with cupric chloride provided the isoxazolium zwitterion, 3 , via an intramolecular cyclization.