Cholesterol → 3beta-Acetoxyandrost-5-en-4,7,17-trione

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The oxidations of testosterone (eq V), 17-acetyltestosterone (eq VI), 4-androstene-3,17-dione (eq VII), and 4-cholesten-3-one (eq VIII) were performed under the same conditions as those reported for the reactions of Table 3. Although using 1,2-dichloroethane as solvent was initially believed to be necessary to dissolve the water-insoluble steroidal compounds, examination of the oxidation process using water as solvent actually led to an improvement in product yield (e.g., 68% yield for 29 after 48 h with 12 equiv of T-HYDRO®). In contrast to oxidations of cholesterol in which the secondary alcohol at the 3-position was stable to oxidative conversion to a ketone, oxidation of the secondary alcohol at the 17-position of testosterone was competitive with allylic oxidation of the enone, and both androst-4-ene-3,17-dione and androst-4-ene-3,6,17-trione accompanied formation of 25. This oxidative process appears to be general for strained secondary alcohols (cyclopentanol, endo-norbornanol, borneol, for example). In an attempt to effect sequential oxidation on both sides of the carbon-carbon double bond, 3β-acetoxyandrost-5-en-17-one was subjected to sequential treatments with TBHP and Rh2(cap)4 (eq IX); the desired 3β-acetoxyandrost-5-en-4,7,17-trione 29 was formed in 54% yield.

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