Chromyl halide oxidation of steroid alkenes

Abstract

Ergosteryl acetate and CrO₂F₂ gave 3β-acetoxy-6α-fluoroergosta-7,22-dien-5α-ol. Cholesteryl acetate and CrO₂Cl₂ gave the α- and β-expoxides, the 5α-chloro-6-ketone, and both 5α,6β-chlorohydrins; cis-chlorohydrins were not detected. Cholesteryl acetate and CrO₂F₂ gave both epoxides and the 5α-fluoro-6β-alcohol. Unexpectedly, 9,11-dehydrotigogenin acetate and CrO₂F² gave only the 9,11-epoxides with the β-form predominating (5 : 1). The absence of cis-halogenohydrin formation from simple olefins and CrO₂X₂(X = F, Cl) is in conflict with recent studies on acyclic and monocyclic alkenes.