Phthalides have been easily prepared by the treatment of methyl o-iodobenzoates with a silylmethyl Grignard reagent in the presence of ketones. The electron-withdrawing ester moiety of methyl o-iodobenzoates and the low nucleophilicity of the silylmethyl Grignard reagent prompted a smooth iodine-magnesium exchange reaction, at room temperature, without affecting the ester moiety or resulting in an undesired reaction with electrophilic ketones. This simple method, wherein special control of the reaction temperature was unnecessary, has allowed the synthesis of various phthalides, including a phenolphthalein derivative.