Br[C:2]1[CH:3]=[C:4]([CH:7]=[CH:8][C:9]=1[OH:10])[CH:5]=[O:6].Cl>[Cu]Cl.C(O)CCC>[CH2:5]([O:6][C:2]1[CH:3]=[C:4]([CH:7]=[CH:8][C:9]=1[OH:10])[CH:5]=[O:6])[CH2:4][CH2:3][CH3:2]4.3 g (188 mmol) of sodium is put at the bottom of a flask under nitrogen and 40 ml of 1-butanol is poured on top. The reaction mixture is stirred and heated progressively up to 120° C.; as the butanolate formed is sparingly soluble, 20 ml of 1-butanol is added. When all the sodium has been consumed, the reaction mixture is brought back to room temperature and 40 ml of dimethylformamide is added. Under nitrogen, 6.8 g (68.2 mmol) of copper(I) chloride is added and then 12.4 g (62 mmol) of 3-bromo-4-hydroxy-benzaldehyde. The reaction mixture is heated progressively to 120° C. and stirred for 2 hours. After cooling to room temperature and then acidifying to pH5 with aqueous hydrochloric acid of concentration 2M, the reaction mixture is extracted with ethyl acetate. The organic phases are combined, washed with saturated sodium chloride solution, dried over magnesium sulfate, filtered, and evaporated. After trituration and then recrystallization of the residue from pentane, 9.7 g (81%) of 3-butoxy-4-hydroxy-benzaldehyde is obtained.
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