7-Ketocholesteryl acetate

A stereospecific acetoxyl group migration reminiscent of that noted in the irradiation of 2,4,6-trimethyl-6-acetoxy-2,4-cyclohexadienone (see Sec. IIB,1) is observed in the irradiation of 7-ketocholesteryl acetate (Formula 205). Irradiation of Formula 205 gives two products (Formulas... 

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. 

Ketazines, 395 Ketene, 76,275 Ketene thioaoetals, 284,413 Ketimines, 345 d-Keto acids, 538 a-Ketocarbenes, 100 7-Ketocholesteryl acetate, 51 5-Keto-6-cyano-5,6-secosteroids, 277... 

The first description of this reagent reported an excellent yield in the oxidation of cholesteryl acetate to 7-ketocholesteryl acetate but subsequent reports have not substantiated this claim. In a modified procedure found to be more satisfactory the reagent is prepared in carbon tetrachloride containing acetic acid and acetic anhydride. Some workers have found even the modified procedure to give poor yields others" have found the reagent us good ns or better than conventional... 

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