1,3-Dibromo-5,5-dimethylhydantoin → 6020-61-7

Participants

Reaction Steps

A suspension of sitosterol acetate (5) (10 g, 21.89 mmol), anhydrous NaHCO3 (9.19 G, 109.45 mmol) and dibromantin in heptane (250 mL) was refluxed for 2 h under argon atmosphere. The reaction mixture was cooled to room temperature and filtered, and then the solvent was removed in vacuo. To the reaction flask, THF (50 mL) was added followed by tetrabutylammonium bromide (0.65 g, 2.02 mmol). The solution was stirred at room temperature for 30 minutes under argon atmosphere. To this reaction mixture tetrabutylammonium fluoride (112 mL, 1 M solution in THF) was added and followed by s-collidine (5 mL). Then the reaction mixture was stirred at room temperature for 20 h. The reaction mixture was diluted with ether (1.5 L), then water (600 mL) was added. The crude reaction mixture was transferred to a separating funnel, the water layer was removed, the organic layer was washed with water (500 mL), 1 N HC1 (2×600 mL), water (600 mL), then brine (500 mL). The organic layer was dried (MgSO4) and concentrated in vacuo to afford a dark brown viscous liquid. The crude reaction mixture was purified by column chromatography (silica gel, ethyl acetate-hexane 1:9 mixture as eluent) to afford 6.5 g, (75%) 7-dehydrositosterol acetate (6) as a pale brown viscous liquid.

Provenance & Evidence