Boron tribromide → 8-Hydroxy-6H-11-oxa-6-aza-benzo[a]fluoren-5-one

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Reaction Steps

8-Methoxy-6H-11-oxa-6-aza-benzo[α]fluoren-5-one (22a) (5.0 g) was cooled using an ice bath, and boron tribromide (1 M in methylene chloride, 95 mL, 95 mmol, 5 eq.) added in a steady stream under nitrogen. The reaction was heated at reflux under inert atmosphere for two hours, then cooled to room temperature and poured into water (150 mL). The resulting suspension was allowed to stir for 1 h, filtered, and the solids were washed with water (2×200 mL). The solids were then diluted with 5 N sodium hydroxide (600 mL) using heating. The resulting solution was cooled to 0° C. using an ice bath and the solution was acidified to pH 1 using conc. HCl. The resulting precipitate was vacuum filtered, and the solids washed sequentially with water (3×300 mL) and diethyl ether (300 mL) then dried overnight using a vacuum oven at 500C to provide Compound 23a as a gray solid. Yield=4.74 g (100%).

Provenance & Evidence