Oxalyl chloride → 3,3-Difluoro-2,2-dimethylbutanoyl chloride

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Reaction Steps

To 1.55 g (9.86 mmol) 3,3-difluoro-2,2-dimethylbutanoic acid in 5 ml of dry dichloromethane was added 3.45 ml (39.5 mmol) of oxalyl chloride. The mixture was stirred at room temperature for 20 hours then solvent and excess reagent removed by distillation followed by addition of carbon tetrachloride and distillation of the solvent. The cooled 3,3-difluoro-2,2-dimethylbutanoyl chloride thus formed was dissolved in 8 ml of dry pyridine and added to a mixture of 2.15 g (4.93 mmol) of [1S-[1α(4R*,6R*),2α, 6β,8β,8aα]]-4-[[(1,1-dimethylethyl)dimethylsilyl]oxy-[2-(1,2,6,7,8,8a-hexahydro-8-hydroxy-2,6-dimethyl-1-naphthalenyl)ethyl]tetrahydro-2H-pyran-2-one, 0.35 g of 4-pyrrolidinopyridine and 10 ml of dry pyridine. The mixture was heated at 50° overnight then cooled and quenched by the addition of ice chips. The mixture was taken up in diethyl ether and washed successively with water, dilute sulfuric acid and saturated sodium bicarbonate. The mixture was dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was chromatographed on silica gel eluting with hexane/dichloromethane/ethyl acetate (25:25:50) to give 0.314 g of 3,3-difluoro-2,2-dimethylbutanoic acid, [1S-[1α,3α,7β,8β(2R*,4R*)8aβ]]-8-[2[tetrahydro-4-[[(1,1-dimethylethyl]dimethylsilyl]oxy]-6-oxo-2H-pyran-2-yl]ethyl]-1,2,3,7,8,8a-hexahydro-3,7-dimethyl-1-naphthalenyl ester.

Provenance & Evidence