Boron tribromide → 9a-butyl-8-chloro-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-7-methoxy-4-(trifluoromethyl)-1,2,9,9a-tetrahydro-3H-fluoren-3-one (32 mg, 0.086 mmol) in anhydrous dichloromethane (0.86 mL) was cooled in a dry ice-acetone bath (−78° C.) and the solution was treated with 1M boron tribromide in dichloromethane (0.258 mL, 0.258 mmol). The cooling bath was removed and the mixture was stirred at room temperature for 95 minutes. Additional 1M BBr3 in CH2Cl2 (0.5 mL, 0.5 mmol) was added and the mixture was stirred at room temperature for an additional 100 minutes. The mixture was partitioned between EtOAc (20 mL) and water (20 mL) containing 2N HCl (3 mL). The organic phase was washed with brine (10 mL), dried over MgSO4, filtered, and evaporated under vacuum. The oily residue was purified by preparative layer chromatography on a 0.1×20×20 cm silica gel GF plate, developing with 5% EtOAc in CH2Cl2. The product band was eluted with EtOAc, the eluent evaporated under vacuum, and the residue lyophilized from benzene to afford 9a-butyl-8-chloro-7-hydroxy-4-(trifluoromethyl)-1,2,9,9a-tetrahydro-3H-fluoren-3-one as an amorphous solid.

Provenance & Evidence