Cholesteryl acetate dibromide

Anodic methoxylation of cyclohexyl isocyanide yields a mixture of six products whose formation is thought to be initiated by methoxy radicals 194). Cholesteryl acetate dibromide has been specifically hydroxylated at C25 in 85 to 93% yield at a lead dioxide anode 19 s. Silyl ethers have been prepared in 60 to 95 % yield by electrolysis of trialkylsilanes at a platinum electrode in ROH- Me4NI,... 

Carboxylation of ketones. In the Robinson-Cornforth1 formal total synthesis of epiandrosterone two relays were utilized. The second was the Koster-Logemann2 ketone (1), available as a by-product of the oxidation of cholesteryl acetate dibromide. Based on model experiments with alicyclic ketones, (1) was converted... 

Chlorotrifluoromethylcarbene, 223 N-Chlorourethane, 60, 61 AM-Cholestadiene-3,6-dione, 60 5a-Cliolestane-3,6-dione, 60 5oCholestane-2a , 3a-oxide, 135 5CfrCholestane-2j3,3(3-oxide, 135 5(3-Cholestanone-3,6-dione, 60 A4-Cholestene-3,6-dione, 60, 65 Al-5/3-Cholestene-3,6-dione, 60 A4-Cholestene-3-one, 98 A4-Cholestene-4-one, 60 -Cholestene-a-epoxide, 116 A5-Cholestenone, 65 Cholesteryl acetate, 35, 171 Cholesteryl acetate dibromide, 40 Chromic acid, 54, 246 Chromic anhydride, 54-57, 150 Chromic anhydride-Acetic acid, 56 Chromic anhydride-Dimethylformamide, 56 Chromic anhydride-Pyridine complex,... 

Cholesteryl acetate dibromide is first prepared by the acetylation of chloesterol and its subsequent bromination. This on oxidation with chromium-6-oxide reduces the 8-carbon side chain at C-17 to a mere CO moiety, which on reduction followed by hydrolysis yields dehydroepiandro-sterone. The resulting product on acetylation protects the acetyl moiety at C-3 and treatment with sodium propoxide introduces a hydroxy group at C-17. Benzoylation followed by mild hydrolysis causes the reappearances of free OH moiety at C-3 and a benzoxy function at C-17. Oppeanauer oxidation cuased by refluxing the resulting secondary alcohol with aluminium tertiary butoxide in excess of acetone affords a ketonic function at C-3, which upon hydrolysis in an alkaline medium yields the official compound. 

AUylic oxidatiau (3, 35). Dr. Thomson has informed us that dioxane is the only suitable solvent for allylic oxidation and that high yield.s arc obtainable only when the double bond is highly hindered, For example, 4,4-dimethylcholesteryl acetate gives a quantitative yield of the 7-keto derivative, and cholesteryl acetate gives 7-ketocholesteryl acetate in 80% yield. However, cholestene-1, -2, and -3 give no products of allylic oxidation, but rather bromohydrins, dibromides, and transformation products therefrom. The use of calcium carbonate is not necessary. 

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