686 mg (3.60 mmol) of copper (I) iodide were added to 24.2 ml (36.3 mmol) of a 1.5M butylmagnesium bromide solution in tetrahydrofuran, whilst cooling in an ice-salt bath, and the resulting mixture was stirred for 15 minutes to form a suspension. A solution of 7.47 g (24.3 mmol) of ethyl 3-(2,4-dimethoxyphenyl)-2-ethoxycarbonyl-2-propenoate (prepared as described in Preparation 1) in 25 ml of tetrahydrofuran was then added dropwise to this suspension at the same temperature over a period of 20 minutes, and the resulting mixture was stirred for 30 minutes. The reaction mixture was then neutralized with concentrated aqueous hydrochloric acid and the resulting mixture was filtered using a Celite (trade mark) filter aid. The filtrate was concentrated by evaporation under reduced pressure, and the concentrate was dissolved in ethyl acetate. The resulting solution was washed three times with a saturated aqueous solution of ammonium chloride and once with a saturated aqueous solution of sodium chloride, after which it was dried over anhydrous sodium sulfate. The solvent was then removed by distillation under reduced pressure, and the resulting residue was purified by column chromatography through 100 g of silica gel, using a gradient elution method, with mixtures of hexane and ethyl acetate ranging from 10:1 to 5:1 by volume as the eluent, to give 9.15 g (a quantitative yield) of diethyl 2-[1-(2,4-dimethoxyphenyl)pentyl]malonate as an oily substance.
