Phenanthro[9,10-d]imidazole derivatives. The structure of Zincke's ‘phenanthraquinone imide anhydride’

Abstract

Condensation of two molecules of phenanthrene-9,10-quinone monoimine (I) in acetic anhydride solution is shown to give dibenzo[c,e]phenanthro[9′,10′:4,5]imidazo[1,2-a]azepine-10-one (VIII), and not dibenzo-[f,h]oxireno[d]phenanthro[9,10-c]cinnoline (II) as previously formulated. Alternative syntheses of the azepinone (VIII) and of one of its reduction products, the parent 10H-dibenzo[c,e]phenanthro[9′,10′:4,5]imidazo[1,2-a]-azepine, are described. Decarbonylation of compound (VIII) gives phenanthro[9′,10′:4,5]imidazo[1,2-f]phen-anthridine (XIV).