Reaction Steps
3-Fluoroestrone was synthesized from 2-aminoestrone by adapting the procedure reported by Doyle and Bryker (J. Org. Chem. 44, 1572-1574, 1979) for the synthesis of arenediaxonium tetrafluoroborate salts from aromatic amines. The procedure is as followed: To neat stirred boron trifluoride etherate (642 μL, 719 mg, 5.07 mmol) at −15° C. under Ar (g) was added a solution of 3-aminoestrone (101) (910 mg, 3.38 mmol) in dry CH2Cl2 (10 mL). After 15 min, a solution of t-butylnitrite (482 μL, 418 mg, 4.05 mmol) in dry CH2Cl2 (5 mL) was dropwise added. The now dark brown solution was stirred at −15° C. for 15 min, then at 0° C. for 30 min. Pentane was added to the solution and a gummy solid precipitated. The solvent was decanted and the residue was dried under vacuum to give a crude light brown solid. The neat solid was heated under vacuum at 70-80° C. in an oil bath for 15 min to give a crude orange solid. Purification by flash chromatography on SiO2 using 1:9 EtOAc/Hexanes gave 3-fluoroestrone (102) as a white solid (437 mg, 47%). M.p. 178° C.; [α]25D +152.0° (c 1.03, CDCl3); IR (ν) 3044, 3039, 2928, 1740 (CO), 1611, 1585, 1495, 1474, 1458, 1428, 1405, 1377, 1340, 1272, 1245, 1230, 1212, 1148, 1094, 1084, 1053, 1008, 908, 889, 817, 784, 718, 704, 642, 620, 580, 564, 467 cm−1; 1H NMR (CDCl3) δ 0.92 (3H, s), 1.37-1.70 (6H, m), 1.93-2.44 (6H, m), 2.52 (1H, dd, J=18.8 Hz, J′=9.0 Hz), 2.91 (2H, dd, J=8.4 Hz, J′=3.8 Hz), 6.82 (2H, dq, J=8.3 Hz, J′=2.8 Hz), 7.23 (1H, dd, J=8.5 Hz, J′=5.8 Hz); 13C NMR (CDCl3) δ 13.8, 21.6, 25.9, 26.3, 29.5, 31.5, 35.9, 38.1, 44.0, 47.9, 50.4, 112.5 (d, J=21.6 Hz), 115.1 (d, J=19.7 Hz), 126.8 (d, J=7.5 Hz), 135.3, 138.7, 161.0 (d, J=244.3 Hz), 220.7.
