Boron tribromide → 10-bromo-2-hydroxy-4H-pyrido[3,2,1-jk]carbazole-4-one

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Reaction Steps

10-bromo-2-methoxy-4H-pyrido[3,2,1-jk]carbazole-4-one (3.2 g) obtained in Example 58 was suspended in anhydrous methylene chloride (500 ml), and boron tribromide (25 g) was added dropwise at room temperature. The mixture was stirred at room temperature for 12 hours and the reaction mixture was poured into ice water (1 L) and the crystals precipitated were recovered by filtration. The methylene chloride layer of the filtrate was washed with saturated aqueous solution of sodium chloride, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure. The two types of crystals thus obtained were combined, and the above-described procedure was repeated. The reaction mixture was poured into ice water (1 L), and the crystals precipitated were recovered by filtration. The crude crystals obtained were washed with a mixed solution of chloroform and methanol at an elevated temperature and recovered by filtration to obtain the title compound (2.4 g, 78%).

Provenance & Evidence