4-Chloro-1,2-dinitrobenzene → Phenol, 5-chloro-2-nitro-

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It is known that the fluorine compound mentioned may be prepared over long reaction times (32 hours) in ethers such as dioxane, using phase transfer catalysis at low temperatures (30° C.) (JP 63310851 A2). Working in water produces an isomeric ratio of about 7:1. Nothing is known from this source about the separation of the isomers. Furthermore, it is known that the chlorine compound may also be prepared in solvent/water mixtures in yields of about 90% (DE 29 39 056). In an earlier known process (DE 29 35 629) aqueous alkali metal hydroxide solutions are used in polar aprotic solvents and emulsifiers (20 hours, 60° C., 81%) for this reaction. Finally it is known that in general 2-nitrohalophenols may be prepared by the reaction of the corresponding nitrohalobenzenes at high temperatures (155° C., 2 hours) in anhydrous media. 4,5-dichloro-2-nitrophenol may be obtained in 77% yield in this way (DE 26 14 264). 2-nitro-5-chlorophenol may be obtained by reacting 4-chloronitrobenzene with KOH at 50° C. in the presence of glass bodies (FR 1 581 400). The same oxidation may be performed in 85-87% yield in solvents, for example 1,2-dimethoxyethane, using phase transfer catalysis (18-crown-6) (Izv. Akad. Nauk. SSSR, Ser. Khim., (11) 2635-2636). Yields of about 90% may be obtained in tertiary alcohols when using aqueous potassium hydroxide solution (6 hours, 60° C.) (JP 52142031). Nitration of 3-chlorophenol has long been known (Uhlemann, Chem. Ber. (1878), 1161; De Kiewiet, Stephen, J. Chem. Soc. (1931), 84). This nitration may also be performed in acetic acid at 0° C. (Roberts, Rhys, J. Chem. Soc. (1937), 39, 41) or using sodium nitrate and dilute sulfuric acid (Hodgson, Moore, J. Chem. Soc. 127 (1925), 1600). A variant is the reaction of 3-chloroaniline with dilute nitric acid (Uhlemann, loc. cit.) or gases containing nitrogen oxides (NOx); however, isomers are produced besides the desired product (v. Auwers, Deines, Fortschr. Ch. Phys. 18, 59; Chem. Zentralblatt, 1924 (II) 2268). In addition, reactions of 4-chloro-1,2-dinitrobenzene with aqueous alkali metal hydroxide solution (Laubenheimer, Chem. Ber. 9 (1876), 768) and of 2-nitro-5-aminophenol with copper(I) chloride in the sense of a Sandmeyer reaction (Phillips, J. Chem. Soc. (1930), 1910, 1913) are known, 2-nitro-5-chlorophenol being obtained.

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