PURPOSE: To prepare the title compound useful as an intermediate of a vat dye, pyranthrone, easily, in high yield and purity, by the dehydrative cyclization of 3- chloro-4-methyl-2-(or 2-chloro-3-methyl-6-)-benzoylbenzoic acid.
CONSTITUTION: 1-chloro-2-methylanthraquinone III is prepared by the dehydrative cyclization of 3-chloro-4-methyl-2-benzoylbenzoic acid I or 2-chloro-3-methyl-6- benzoylbenzoic acid II, which comprises heating the above starting compound pref. at 80-130°C, esp. 100-110°C, for 1-5 hours in the presence of a dehydration condensation agent such as sulfuric acid, fuming sulfuric acid, polyphosphoric acid, phosphorus pentoxide, anhydrous hydrogen fluoride, etc. The starting compound I or II is obtained in high yield, by the Friedel-Crafts reaction of benzene and 3- chloro- 4-methyl phthalic anhydride, which is obtained by the chlorination of 4- metyl phthalic anhydride.
NISHIZAWA ISAO
HASEGAWA KIYOHARU
ABE NOBUYOSHI
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