Hydrochloric Acid → (2-Methylpropyl) (2,4,5-trihydroxyphenyl) ketone

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In a vessel fitted with a calcium chloride tube, 12.61 g (100.0 mmol) of hydroxyhydroquinone (2) was suspended in 110 ml of nitrobenzene and stirred at room temperature. Into this, 40.0 g (300 mmol, 3.00 equivalents) of granular aluminum chloride was added piecemeal. They were further stirred for one hour and then 12.06 g (100.0 mmol, 1.00 equivalent) of isovaleryl chloride was slowly added dropwise. As the reaction mixture became a reddish purple amorphous solid 10 hours after the addition, it was mechanically crushed into fine fragments. The fine fragments were poured into 500 ml of a cold 2 M hydrochloric acid solution, stirred for 30 minutes, and extracted from ether. The ether layer was washed with water, distilled to remove the solvent, combined with a large volume of water, and distilled water under reduced pressure to remove nitrobenzene by steam distillation method. The residue of the distillation was dissolved in ether, washed with saturated brine, dried over sodium sulfate, distilled under a reduced pressure to remove ether and obtain a crude reaction product. By recrystallizing the crude product from hexane-petroleum ether (2:1), 18.3 g (yield 86.6%) of the product (7) was obtained in the form of reddish purple crystals of thin needles.

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