(Trifluoromethyl)trimethylsilane → (2R,3R)-3-(tert-Butyl-dimethylsilanyloxy)-2-[(1R)-(2,2,2-trifluoro-1-hydroxyethyl)]pyrrolidine-1-carboxylic acid tert-butyl ester

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Reaction Steps

To (2S,3R)-3-(tert-butyldimethylsilanyloxy)-2-formylpyrrolidine-1-carboxylic acid tert-butyl ester (7C) (2.10 g, 6.38 mmol) was added trimethyl(trifluoromethyl)silane (800 μL, 6.57 mmol) and cesium fluoride (dried under high vacuum at 130° C. for 12 h) (10.0 mg, 0.066 mmol). The reaction was stirred at rt for 24 h then heated to 50° C. for 5 h. After cooling to rt, 4N HCl (ca. 10 mL) was added and the reaction was stirred overnight. The brown aqueous solution was decanted and the remaining waxy yellow solid was dried under high vacuum overnight then recrystallized from hexane to provide (2R,3R)-3-(tert-butyldimethylsilanyloxy)-2-[(1R)-(2,2,2-trifluoro-1-hydroxyethyl)]-pyrrolidine-1-carboxylic acid tert-butyl ester (7D) (1.19 g) as a white solid. The mother liquor was concentrated and purified via flash chromatography eluting with 5-20% EtOAc/hexane to provide (2R,3R)-3-(tert-butyldimethylsilanyloxy)-2-[(1S)-(2,2,2-trifluoro-1-hydroxy-ethyl)]-pyrrolidine-1-carboxylic acid tert-butyl ester (7E) (192 mg) as an oil and a mixture of (2R,3R)-3-(tert-butyldimethylsilanyloxy)-2-[(1R)-(2,2,2-trifluoro-1-hydroxy-ethyl)]-pyrrolidine-1-carboxylic acid tert-butyl ester (7D) and starting material (306 mg). The latter was recrystallized from hexane to provide additional (2R,3R)-3-(tert-butyldimethylsilanyloxy)-2-[(1R)-(2,2,2-trifluoro-1-hydroxy-ethyl)]-pyrrolidine-1-carboxylic acid tert-butyl ester (7D) (100 mg).

Provenance & Evidence