A solution of 2.7 g of difluoromethyldiphenylphosphine oxide in 85 ml of tetrahydrofuran is slowly mixed with 5.3 ml of 2 M lithium diisopropylamide solution at a bath temperature of -50° C., and it is stirred for 1 hour. Then, a solution of 1.5 g of 3-tetrahydropyranyloxy-estra-1,3,5(10),8-tetraen-17-one in 42 ml of tetrahydrofuran is slowly added, stirred for 15 minutes, slowly heated at a bath temperature of from -50° C. to 100° C. and refluxed for 2.5 hours. For working-up, it is diluted with ethyl acetate and water, washed with water, dried on sodium sulfate, concentrated by evaporation in a vacuum and chromatographed on silica gel with hexane/ethyl acetate. 1.0 g of 17-difluoromethylene-3-tetrahydropyranyloxy-estra-1,3,5(10),8-tetraene is obtained as colorless crystals with a melting point of 124-125° C., [α]D22 =+2.0° (c=0.525% in pyridine).
