The reaction of ethyl magnesium bromide and 17 alpha-ethynylestradiol with formaldehyde in the presence of triethyl phosphate or hexamethylphosphoramide gave the 2- and 4-formyl-17 alpha-ethynylestradiol in high yield. Treatment of the formyl derivatives with an alkaline solution of hydrogen peroxide in tetrahydrofuran afforded the corresponding catechols in almost quantitative yield. This new synthetic method was far superior to other methods, especially concerning simplicity, selectivity, and high yields.