Sodium Thiosulfate → HCID 70167631, compound

Participants

Reaction Steps

xi)—A mixture of (3β,20S)-20-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-4,4-dimethylpregn-5-en-3-ol benzoate (44.6), dry toluene (394 ml), dry cyclohexane (394 ml) and N-bromosuccinimide (17.8 g) was heated at reflux temperature for 10 min. The reaction mixture was cooled, another portion of N-bromosuccinimide (17.8 g) was added, and reflux was continued for another 10 min. The reaction mixture was cooled, a saturated aqueous solution of sodium thiosulfate (802 ml) was added and the resulting mixture was stirred for 30 min. The organic phase and the aqueous phase were separated and the latter extracted two times with toluene. The combined organic phases were dried over sodium sulfate and concentrated under reduced pressure. A solution of the crude product thus obtained in dry toluene (1381 ml) and N,N-diisopropylethylamine (138 ml) was heated under reflux for 1.5 h. Then it was cooled and washed with a saturated aqueous solution of sodium hydrogen carbonate, a saturated aqueous solution of ammonium chloride and with brine, the aqueous phase each time being extracted with ethyl acetate. The combined toluene and ethyl acetate solutions were dried over sodium sulfate and concentrated under reduced pressure. Column chromatography afforded (3β,20S)-20-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-4,4-dimethylpregna-5,7-dien-3-ol benzoate (compound 12a; 40.0 g).

Provenance & Evidence