The condensation of 4,4'-dimethoxybenzophenone (I) with ethyl 4-bromo-4-cyanobutyrate (II) by means of trimethyl borate, Zn and I2 in THF gives ethyl 4-cyano-5,5-bis(4-methoxyphenyl)-4-pentenoate (III), which is saponified with NaOH in hot dioxane-water.