Metal Ion Catalyzed Oxidation of Steroids. III. Reactions of Cholesterol with Ferrous Ions- and Titanous Ions-Hydrogen Peroxide Systems in Acetonitrile

Abstract

The reactions of cholesterol (I) with hydrogen peroxide in the presence of transitionmetal salts were carried out at moderate temperature in an acetonitrile medium. When ferrous or titanous sulphate was employed, 5, 6α-epoxy-5α-cholestan-3β-ol (II) (and/or epimeric β-epoxide, XII), 5α-cholestane-3β, 5, 6β-triol (III), cholest-5-ene-3β, 7α-diol (IV), and cholest-5-ene-3β, 7β-diol (V) were formed in rather poor yields. The radical scavenger, α-tocopherol, inhibited the hydroxylation at the allylic position and thus no formation of IV and V was observed. On the contrary, titanium trichloride-hydrogen peroxide system was found to consume entirely the substrate (I) giving considerable amounts of III and the chlorinated products such as 5, 6β-dichloro-5α-cholestan-3β-ol (VI), 5-chloro-5α-cholestane-3β, 6β-diol (VII), 6β-chloro-5α-cholestane-3β, 5-diol (VIII), and 6α-chloro-5β-cholestane-3β, 5-diol (IX). The epoxides (II and XII) were separated solely as the artifacts from the monochlorides (VII and VIII) through column chromatography on alumina. The yields of III, VI, the mixture of VII and VIII, and of IX were in an approximate ratio of 2 : 1 : 2 : 4.