Hydrochloric Acid → 1,4-Difluoro-5,8-dihydroxyanthraquinone

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This compound was prepared by modifications to the literature method of Synth. Comm., 1990, 20, 2139. A mixture of the sublimed product (9) from the above reaction (100 g, 0.55 moles), hydroquinone (63.7 g, 0.58 moles), NaCl (127 g, 2.22 moles) and powdered anhydrous AlCl3 (833 g, 6.26 moles) was placed in a 5 L flask equipped with a condenser. The reactants were well-mixed by shaking, then heated over 1-2 hours to 200±5° C. (bath) under a nitrogen atmosphere (there was very large gas evolution during the heating process). After a further 2 hours at 200±5° C., the melt was poured onto ice and conc. HCl (1.6 L) was added. The mixture was stirred at room temperature overnight, and the reddish brown precipitate was collected, washed with H2O and dried to give crude 1,4-difluoro-5,8-dihydroxyanthracene-9,10-dione (4) (151 g, 98%), m.p. 301-304° C. (lit. m.p. 318-319° C.). This crude product was virtually insoluble in all solvents, and showed (by TLC in EtOAc/petroleum ether 1:3) only one minor impurity (probably 1-chloro-4-fluoro-5,8-dihydroxyanthracene-9,10-dione). 1H NMR agreed well with literature. This material was used for the next step without further purification.

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