反应详情

In the process of the French Pat. No. 1,486,803, 5-nitrotetrahydroanthraquinone produced is directly subjected to oxidation, without isolation from reaction system, into 1-nitroanthraquinone. Accordingly, when crude 5-nitronaphthoquinone is used as a starting material, 6-nitroanaphthoquinone is converted into 2-nitronaphthoquinone through 6-nitrotetrahydroanthraquinone, thus contaminating 1-nitroanthraquinone and lowering the purity thereof. Further, it is difficult to obtain highly pure 1-aminoanthraquinone from the thus contaminated 1-nitroanthraquinone. This process also requires an additional step of purifying the starting material or the product so as to obtain highly pure 1-nitroanthraquinone or 1-aminoanthraquinone. In this connection, we have found as a result of an experiment that when crude 5-nitronaphthoquinone is condensed with 1,3-butadiene in nitrobenzene and the resulting product is separated or isolated from the reaction system by filtration, most of 6-nitrotetrahydroanthraquinone produced from 6-nitronaphthoquinone is removed in a state of being dissolved in the solvent, so that there can be obtained highly pure 5-nitrotetrahydroanthraquinone, from which 1-nitroanthraquinone or 1-aminoanthraquinone with high purity can be prepared. However, this process is also industrially disadvantageous in that the dissolution loss of 5-nitrotetrahydroanthraquinone in solvent is large, it's yield being considerably reduced.