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Compound 8a was prepared using a reported procedure. (See, Kalvoda, J., et al., Reactions of Steroid Hypoiodites. VII. 1,4-Shift of the Nitrile Group (18-Cyanopregnanes), Helv. Chim. Acta 1966, 49: 424-436) I2 (1.6 g, 6.30 mmol) was added to a refluxing mixture of Pb(OAc)4 (6.0 g, 13.5 mmol) and CaCO3 (2 g, 20.0 mmol) in cyclohexane (200 mL). The purple solution was refluxed for 1 h and the mixture of compound 6a and 7a obtained in last step [prepared from 6a (1.0 g, 2.77 mmol)] was added. The reaction mixture was refluxed while irradiated with a 300 W tungsten lamp for 3 h and then cooled to room temperature. After filtration, the precipitate was washed thoroughly with ether. The combined filtrate was washed successively with 10% Na2S2O3 and brine, and dried over Na2SO4. Removal of solvent under reduced pressure gave a residue which was purified by column chromatography (silica gel; hexanes/EtOAc, 4:1) to give compound 8a (400 mg, 40% from 6a) and recovered compound 6a (400 mg).

1. temperatureThe purple solution was refluxed for 1 h