Cyclohexane → Ethyl(3R)-2-(4-ethylphenyl)-4,4,4-trifluoro-3-methylbutanoate

Participants

Reaction Steps

24.4 ml (24.4 mmol) of a 1 M solution of lithium hexamethyldisilazide in toluene were cooled to −10° C., and a solution of 3.0 g (16.29 mmol) of ethyl (3R)-4,4,4-trifluoro-3-methylbutanoate in 15 ml of abs. toluene was added dropwise. The mixture was stirred for 10 min. At −10° C., a solution, prepared beforehand, of 3.92 g (21.18 mmol) of 1-bromo-4-ethylbenzene, 110 mg (0.49 mmol) of palladium(II) acetate and 404 mg (1.03 mmol) of 2′-dicyclohexylphosphino-2-(N,N-dimethylamino)biphenyl in 20 ml of abs. toluene was then added dropwise. The resulting reaction mixture was stirred initially at RT for 1 h, then at 80° C. for 3 h. The mixture was then concentrated under reduced pressure and the residue was taken up in ethyl acetate and added to water. The aqueous phase was back-extracted with ethyl acetate, and the combined organic phases were washed with saturated ammonium chloride solution and saturated sodium chloride solution, dried over magnesium sulphate and concentrated under reduced pressure. The residue gave, after chromatography on silica gel (mobile phase: initially cyclohexane, then gradient cyclohexane/ethyl acetate 200:1→50:1), 3.051 g of the title compound (64.9% of theory, diastereomer ratio about 3:1).

Provenance & Evidence