Friedel Crafts condensation of p-dimethoxybenzene (I) with dichloromaleic anhydride (II) in a molten mixture of AlCl3 and NaCl yielded dichloronaphthazarin (III). Finally, treatment of (III) with resorcinol (IV) and Na2CO3 in DMSO at room temperature furnished the target compound.
Friedel Crafts condensation of p-dimethoxybenzene (I) with dichloromaleic anhydride (II) in a molten mixture of AlCl3 and NaCl yielded dichloronaphthazarin (III). Subsequent methylation of (III) with CH3I in the presence of Ag2O in CHCl3 gave a mixture of dimethoxy naphthoquinones (IV) and (V), from which the desired isomer (IV) was isolated by recrystallization from CHCl3-CCl4. Finally, treatment of (IV) with 3-methoxyphenol (VI) and Na2CO3 in DMSO at room temperature furnished the target compound.
Friedel Crafts condensation of p-dimethoxybenzene (I) with dichloromaleic anhydride (II) in a molten mixture of AlCl3 and NaCl yielded dichloronaphthazarin (III). Subsequent methylation of (III) with CH3I in the presence of Ag2O in CHCl3 gave a mixture of dimethoxy naphthoquinones (IV) and (V), from which the desired isomer (IV) was isolated by recrystallization from CHCl3-CCl4. Finally, treatment of (IV) with 3,5-dimethoxyphenol (VI) and Na2CO3 in DMSO at room temperature furnished the target compound.