Hydrochloric Acid → 4-Cyclopentylbutan-2-one

10 parts of 3-cyclopentyl propionic acid are dissolved in 150 parts by volume of ethyl ether and chilled to -20° C. under argon. 50 parts by volume of 2.8 molar methyl magnesium bromide are added dropwise. After the addition of the methyl magnesium bromide is completed, the mixture is allowed to warm to room temperature. The cloudy reaction mixture is treated with 1N hydrochloric acid and the clearified reaction mixture is extracted with ether followed by ethyl acetate. The combined organic extracts are washed with water and saturated sodium chloride solution, dried over anhydrous sodium sulfate, filtered and the solvent evaporated under reduced pressure. The residual oil is chromatographed on silica gel using 10% ethyl acetate/hexane as the eluent, to provide 4-cyclopentyl-2-butanone.