The fluorination reaction was carried out in a 10 mm NMR tube. To 0.28 mmol of the estratrien methyl ether were added 2.5 ml of CDCl3 by vacuum transfer. The mixture was warmed to room temperature forming a colorless solution. This solution was cooled to -196° C. and 0.28 mmol each of FN(SO2CF3)2 and CFCl3 were added by vacuum transfer. The tube was sealed and warmed to -74° C. and then to 22° C. over a 2 hour period. Near -65° C., the colorless solution began to turn to a pale yellow color. After reaching 22° C., 19F NMR indicated a quantitative amount of (CF3SO2)2NH was formed. Two other fluorine resonances are observed in the ratio of 1:1 with a total area equal to the internal CFCl3 standard. These resonances at -140.2(m) and -168.6(m) ppm relative to CFCl3 are assignable to an equimolar mixture of the two monofluoro derivatives of the estratrien, 2-fluoro1,3,5(10)estratrien-3ol-17one methyl ether and 4-fluoro1,3,5(10)estratrien-3ol-17one methyl ether, respectively.
