Chlorotrimethylsilane → (3S,4R)-3-[(R)-1-[(tert-butyldimethylsilyl)oxy]ethyl]-4-[(S)-2-oxo-3-cyclohexen-1-yl]azetidin-2-one

Participants

Reaction Steps

To stannous chloride (379 mg) was added a dichloromethane solution (10 ml) of chlorotrimethylsilane (217 mg) followed by addition of a dichloromethane solution (10 ml) of (3R,4R)-4-acetoxy-3-[(R)-1-[(tert-butyldimethylsilyl)oxy]ethyl]-1-trimethylsilylazetidin-2-one (7.19 g). To this suspension was added a dichloromethane solution (10 ml) of 2-[(trimethylsilyl)oxy]-1,3-cyclohexadiene (4.05 g) dropwise at room temperature over a period of 1 hour. The mixture was stirred at 25° C. for 2 hours, at the end of which time a dichloromethane solution (10 ml) of 2-[(trimethylsilyl)oxy]-1,3-cyclohexadiene (5.38 g) was added dropwise over a period of 1 hour. The mixture was further stirred for 5 hours and then allowed to stand at 0° C. overnight. The solvent was then distilled off under reduced pressure. To the residue were added ether (100 ml) and aqueous sodium hydrogen carbonate solution (30 ml) and the mixture was stirred for 10 minutes. The insolubles were filtered off and the aqueous layer was extracted with ether. The ether layer was washed with saturated aqueous sodium chloride solution and dried over anhydrous sodium sulfate. The solvent was then distilled off under reduced pressure and the residue was dissolved in THF-water (17:2, 95 ml). To this solution was added pyridinium p-toluenesulfonate (610 mg) and the mixture was stirred at room temperature for 1 hour. The solvent was distilled off under reduced pressure and ether (150 ml) was added to the residue. The organic layer was washed successively with water and saturated sodium chloride solution and dried over anhydrous sodium sulfate. The solvent was then distilled off under reduced pressure and the residue was purified by flash column chromatography (packing: silica gel 300 g; ether-hexane 5:1) to give (3S,4R)-3-[(R)-1-[(tert-butyldimethylsilyl)oxy]ethyl]-4-[(R)-2-oxo-3-cyclohexen-1-yl]azetiidin-2-one (R-compound; 1.01 g) and (3S,4R)-3-[(R)-1-[(tert-butyldimethylsilyl)oxy]ethyl]-4-[(S)-2-oxo-3-cyclohexen-1-yl]azetidin-2-one (S-compound; 0.96 g).

Provenance & Evidence