Studies on Heterocyclic Colouring Matters Part III: 7a,14a‐diaza‐7,7a,14,14a‐tetrahydroquino[2,3‐b]acridine‐7,14‐diones (5,7a,12,14a‐tetraaza‐7,7a,14,14a‐tetrahydropentacene‐7,14‐diones)

Abstract

2-Aminopyridines react with diethyl 2,5-dioxo-cyclohexane-1,4-dicarboxylate (diethyl succinylsuccinate) to give 7a, 14a-diaza-6,7,7a, 13,14,14a-hexahydroquino-[2,3-b]acridine-7, lbdiones (5,7a, 12,14a-tetraaza-6,7,7a, 13,14,14a-hexahydropentacene-7,14-diones), which are aromatized to the title compounds. Oxidation of these with a mixture of sulfuric and nitric acids results in the formation of their respective 6,13-quinones, also obtained directly from 2-aminopyridines and diethyl 2,Sdichloro-1,4-benzoquinone-3,6-dicarboxylate. The chromophore of the title compounds is compared with that of quinacridones.