Mitsui Toatsu Chemicals, Incorporated

Seishichiro Kaba

Ken Mukai

Yasuyoshi Torisu

Highly pure 5-nitro-1,4,4a,9a-tetrahydroanthraquinone can be obtained by subjecting 6-nitronaphthoquinone-containing crude 5-nitro-1,4-naphthoquinone to Diels-Alder condensation reaction with 1,3-butadiene in a solvent including benzene, an alkylated aromatic hydrocarbon such as toluene, xylene or the like, a halogenated aromatic hydrocarbon such as chlorobenzene, dichlorobenzene, or the like, or a halogenated aliphathic hydrocarbon such as trichloroethylene, perchloroethylene or the like, cooling the resulting reaction solution to crystallize the reaction product, and separating the thus crystallized product by filtration. 5-nitro-1,4,4a,9a-tetrahydroanthraquinone has a relatively small solubility in the above-mentioned solvents, while the solubility of 6-nitro-1,4,4a,9a-tetrahydroanthraquinone in the solvents is rather great, thus the above-mentioned solvents being effective for the separation of these compounds from each other. The oxidation and the subsequent reduction of the thus obtained 5-nitro-1,4,4a,9a-tetrahydroanthraquinone yields 1-aminoanthraquinone with a purity above 98 wt% and a 2-aminoanthraquinone content below 1 wt%. The above-mentioned solvents are also effective for purification of 6-nitro-1,4,4a,9a-tetrahydroanthraquinone-containing 5-nitro-1,4,4a,9a-tetrahydroanthraquinone by recrystallization.

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Arao, Japan

Seishichiro Kaba