Electrophilic Fluorination with F-TEDA-BF4 Selectfluor

Electrophilic Fluorination with F-TEDA-BF4 (Selectfluor) A.3.1 Synthesis of the Fluorosteroid 11 

A solution of 3 -acetoxyandrosterone (9) (0.5 g, 1.52 mmol) in isopropenyl acetate (5.0 mL) was heated at 80 °C for 24 h under Nj. The reaction was cooled and quenched by addition of 200 pL triethylamine. The solvent was removed by distillation in vacuo (0.1 mmHg), and the residue (10) was dissolved into acetonitrile (25 mL). F-TEDA-BF4 (537 mg, 1.52 mmol) was added and the reaction was monitored by TLC (ethyl acetate/hexane 1 4). After 2 h the solution was poured into ethyl acetate (25 mL), washed with water (3 X 25 mL), dried (MgS04), fdtered, and evaporated in vacuo. Flash chromatography of the residue on silica gel (ethyl acetate/hexane 1 4) afforded 474 mg (90%) of 3/9-acetoxy-16-fluoroandrostrone (11) (alfS = 94 6), which had spectroscopic properties consistent with those reported in the literature [9]. 

A solution of diethyl phenylmalonate (12) (1 mmol) in THF (50 mL) was added to an oil-free suspension of NaH (40 mg of 60%, 24 mg, 1 mmol) in THF (5.0 mL) under N2 at 0°C. The solution was stirred at 0°C for 30 min and then at room temperature for 1 h. The sodium salt was diluted with DMF (2.0 mL) and F-TEDA-BF4 (354 mg) was added. After being stirred for 30 min at room temperature the mixture was poured into EtjO, washed with 5 % H2SO4 (10 mL) and 

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