Hydrochloric Acid → 2-Bromo-7-hydroxyphenanthrene

関与物質

反応手順

25.0 g (74.4 mmol) of 2,7-dibromophenanthrene (CAS No. 62325-30-8) and 24.0 ml (104 mmol) of triisopropyl borate are initially introduced in 750 ml of THF, and 61 ml (97 mmol) of a 15 percent solution of n-butyllithium in hexane are added dropwise at −70° C. When the addition is complete, the batch is left to stir for a further 1 h, hydrolysed using 2 N hydrochloric acid, and the cooling is removed. After addition of MTB ether, the aqueous phase is removed and extracted with MTB ether. The combined org. phases are dried over sodium sulfate, evaporated, and the residue is recrystallised from heptane. 30 ml of 30 percent hydrogen peroxide are added to the resultant boronic acid in 350 ml of toluene and 150 ml of 2 N sodium hydroxide solution with vigorous stirring at such a rate that the temp. does not exceed 45° C. When the addition is complete, the batch is left to stir for a further 30 min, added to 200 ml of water and acidified using 2 N hydrochloric acid. The aqueous phase is separated off and extracted three times with ethyl acetate. The combined org. phases are washed with dil. ammonium iron(II) sulfate solution and water and dried over sodium sulfate. The solvent is removed in vacuo, and the residue is filtered through silica gel with dichloromethane and recrystallised from toluene, giving 2-bromo-7-hydroxyphenanthrene as colourless crystals.

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