Reaction #42654

Reaction equation

boron trifluoride etherate

hexane ethyl acetate dichloromethane methanol

(11β,16β)-21-(acetyloxy)-9-fluoro-16-methyl-3,20-dioxo-11-[(trimethylsilyl)-oxy]pregna-1,4-dien-17-yl ethylcarbamate

boron trifluoride etherate

→

(11β,16β)-21-(acetyloxy)-9-fluoro-11-hydroxy-16-methyl-3,20-dioxopregna-1,4-dien-17-yl ethylcarbamate

Solvents

acetonitrile

Conditions

Workup

1. 1
   workup.STIRRINGThe solution was stirred at room temperature for 15 hours more
2. 2
   Otherwas then partitioned between ethyl acetate and water
3. 3
   WashThe organic layer was washed with water (twice) and brine
4. 4
   Dryingdried over Na2SO4
5. 5
   FiltrationFiltration and evaporation under vacuum
6. 6
   Othergave a pale yellow oil

Procedure

To a solution of (11β,16β)-21-(acetyloxy)-9-fluoro-16-methyl-3,20-dioxo-11-[(trimethylsilyl)-oxy]pregna-1,4-dien-17-yl ethylcarbamate (138 mg, 0.239 mmol) in 2.5 mL of acetonitrile was added boron trifluoride etherate (0.12 mL, 0.96 mmol). After stirring at room temperature for 5 hours, additional boron trifluoride etherate (0.060 mL, 0.47 mmol) was added. The solution was stirred at room temperature for 15 hours more and was then partitioned between ethyl acetate and water. The organic layer was washed with water (twice) and brine and dried over Na2SO4. Filtration and evaporation under vacuum gave a pale yellow oil. Chromatography on silica gel eluting with hexane/ethyl acetate/dichloromethane/methanol (5:2:2:1) gave (11β,16β)-21-(acetyloxy)-9-fluoro-11-hydroxy-16-methyl-3,20-dioxopregna-1,4-dien-17-yl ethylcarbamate as a white film.

Source