反应详情

In an inert water-free solvent, e.g. in dichloromethane in the presence of a strong acid, e.g. conc. sulphuric acid or p-toluene sulphonic acid, preferably conc. sulphuric acid and water-binding auxiliary material, e.g. trimethyl-ortho-formiate 4-(4-fluor-benzoil)-butyric acid (II) is reacted in one step with ethylene glycol at a 20-25° C. temperature. The reaction is stopped with addition of a base, e.g. NaHCO3. The solvent is changed to an alcoholic one, preferably to methanol, and the formed ester intermediate (III) is hydrolyzed by a base solution, preferably with potassium hydroxide solution. The formed 4-[2-(4-fluoro-phenyl)-[1,3]dioxolane-2-yl]-butyric acid (IV) is isolated after the concentration of the reaction mixture, then acidification with a weak acid, e.g. with tartaric acid, citric acid, preferably citric acid followed an extraction with an appropriate solvent, e.g. ethyl acetate. The product is purified by crystallization from an apolar solvent, e.g. from n-hexane or n-heptane.