(+/-)-ethyl (2,2-difluorocyclopentyl)acetate

Conditions: temp:-20.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 22.6 ml (22.6 mmol) of a 1 M solution of lithium hexamethyldisilazide in toluene were cooled to −20° C., and a solution of 2.90 g (15.09 mmol) of (+/−)-ethyl (2,2-difluorocyclopentyl)acetate in 20 ml of abs. toluene was added dropwise. The mixture was stirred at −20° C. for 10 min Cooling was removed, and a solution, prepared beforehand, of 3.75 g (19.61 mmol) of 4-bromo-chlorobenzene, 110 mg (0.49 mmol) of palladium(II) acetate and 374 mg (0.95 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, and then at 90° C. for 2 h. After cooling, the reaction mixture was added to water. The aqueous phase was extracted three times with ethyl acetate, and the combined organic phases were dried over magnesium sulphate and concentrated under reduced pressure. The residue gave, after chromatography on silica gel (mobile phase cyclohexane/ethyl acetate 50:1), 2.70 g of the title compound (59.1% of theory, diastereomer ratio about 1:4.3). Cooling was removed a solution, prepared beforehand The resulting reaction mixture was stirred initially at RT for 1 h at 90° C. for 2 h After cooling The aqueous phase was extracted three times with ethyl acetate the combined organic phases were dried over magnesium sulphate concentrated under reduced pressure The residue gave