Boron tribromide → 9a-butyl-8-chloro-6-fluoro-7-hydroxy-4-(trifluoromethyl)-1,2,9,9a-tetrahydro-3H-fluoren-3-one

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Reaction Steps

A solution of 9a-butyl-8-chloro-6-fluoro-7-methoxy-4-(trifluoromethyl)-1,2,9,9a-tetrahydro-3H-fluoren-3-one (39 mg, 0.10 mmol) in anhydrous dichloromethane (1.0 mL) was cooled in a dry ice-acetone bath (−78° C.) and the solution was treated with 1M boron tribromide in dichloromethane (0.3 mL, 0.3 mmol). The cooling bath was removed and the mixture was stirred at room temperature for one hour. The mixture was partitioned between EtOAc (20 mL) and water (20 mL) containing 2N HCl (1 mL). The organic phase was washed with brine (10 mL), dried over MgSO4, filtered, and evaporated under vacuum. The residue was purified by preparative layer chromatography on a 0.1×20×20 cm silica gel GF plate, developing with 10% EtOAc in CH2Cl2. The product band was eluted with 10% MeOH in CH2Cl2, the eluent evaporated under vacuum, and the residue lyophilized from benzene plus a few drops of EtOH to afford 9a-butyl-8-chloro-6-fluoro-7-hydroxy-4-(trifluoromethyl)-1,2,9,9a-tetrahydro-3H-fluoren-3-one as an amorphous solid.

Provenance & Evidence