The reduction of 1,4-dihydroxy-9,10-anthraquinone (I) with NaBH4 in methanol gives 1,4-anthraquinone (II), which is reduced with Na2S2O4 in dioxane/water to yield 1,4-anthracenediol (III). The methylation of (III) with NaH and Me-I in DMF affords 1,4-dimethoxyanthracene (IV), which is condensed with 2-methoxy-1,4-benzoquinone (V) (obtained by oxidation of 2-methoxyhydroquinone (VI) with Ag2O and K2CO3 in benzene) by heating at 150 C with toluene in a sealed tube to provide the triptycene derivative (VII). The reaction of (VII) with KOH in dioxane/water gives the triptycenediol (VIII), which is oxidized with Ag2O in refluxing acetone to yield the triptycenequinone (IX). Finally, this compound is oxidized with Ce(NH4)2(NO3)6 to afford the target triptycenediquinone.
The reduction of 1,4-dihydroxy-9,10-anthraquinone (I) with NaBH4 in methanol gives 1,4-anthraquinone (II), which is reduced with Na2S2O4 in dioxane/water to yield 1,4-anthracenediol (III). The methylation of (III) with NaH and Me-I in DMF affords 1,4-dimethoxyanthracene (IV), which is condensed with 2-methoxy-1,4-benzoquinone (V) (obtained by oxidation of 2-methoxyhydroquinone (VI) with Ag2O and K2CO3 in benzene) by heating at 150 C with toluene in a sealed tube to provide the triptycene derivative (VII). The reaction of (VII) with KOH in dioxane/water gives the triptycenediol (VIII), which is oxidized with Ag2O in refluxing acetone to yield the triptycenequinone (IX). The bromination of (IX) with NBS in hot DMF affords the bromo derivative (X), which is finally oxidized with Ce(NH4)2(NO3)6 to afford the target triptycenediquinone.
The Diels-Alder cycloaddition between 1,4-dimethoxyanthracene (IV) and methoxyhydroquinone (V) in the presence of Ag2O and ZnI2 yields the triptycene quinone (VI). This compound has also been obtained by stepwise oxidation of (V) to methoxybenzoquinone (VII) with Ag2O, followed by Diels-Alder condensation with 1,4-dimethoxyanthracene (IV) to produce adduct (VIII) as a mixture of two stereoisomers. After isomerization of ketones (VIII) with KOH, oxidation with Ag2O leads to quinone (VI). Mono-quinone (VI) is oxidized to the bis-quinone (IX) employing ceric ammonium nitrate. Then, regioselective bromination of (IX) with N-bromosuccinimide (NBS) furnishes bromoquinone (X). Alternatively, compound (XI) is obtained from the bromination of (VI) with NBS, followed by oxidation with ceric ammonium nitrate). When bis-quinone (X) in THF solution is treated with dimethylamine gas (containing small amounts of methylamine), the title compound is obtained a regioisomeric mixture of methylamino derivatives, along with the expected dimethylamino analogues, which are separated by column chromatography.
Reduction of quinizarin (I) with NaBH4 in MeOH, followed by quenching with HCl provides 1,4-anthraquinone (II). This is further reduced to 1,4-dihydroxyanthracene (III) employing sodium hydrosulfite in dioxane. Subsequent methylation of diol (III) with iodomethane and NaH leads to the key intermediate 1,4-dimethoxyanthracene (IV).