(Diethylamino)sulfur trifluoride → 5alpha-Androst-2-en-17-one

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To a solution of epiandrosterone (150 mg, 0.517 mmol) in anhydrous dichloromethane (11 mL) at −78° C. under argon atmosphere was added diethylaminosulfur trifluoride (DAST) (0.082 mL, 0.620 mmol) and the resulting solution stirred for 1 h at −78° C. The solution was then directly evaporated with silica gel and purified by FCC with EtOAc/hexanes (1:99) as eluant to give the desired compound 2 (42 mg, 30%) with a ratio of C2-C3 alkene vs. C3-C4 alkene isomer of less than 90:10. 1H NMR (CDCl3) δ: 0.78 (s, 18-CH3), 0.87 (s, 19-CH3), 0.9-2.0 (residual CH and CH2), 2.06 (m, 16α-CH), 2.44 (dd, J1=8.8 Hz and J2=19.2 Hz, 16β-CH), 5.59 (m, 2-CH and 3-CH). 13C NMR (CDCl3) δ: 11.6, 13.7, 20.2, 21.7, 28.4, 30.2, 30.6, 31.5, 34.7, 35.1, 35.8, 39.7, 41.4, 47.7, 51.4, 54.1, 125.7, 125.8, 221.5. LRMS for C19H29O [M+H]+: 273.1 m/z.

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