Side-chain inversion of steroidal olefins promoted by hydrogen chloride

The reaction of hydrogen chloride on 7-, 8(14)-, and 14-ene steroids was investigated. A 14α-chloro compound is the product of kinetically controlled addition of the acid. A 14β-chloro compound with the side chain in the 17α configuration originates in diethyl ether at temperatures lower than -30°C in the presence of hydrogen chloride, via a carbocation at C14. There is evidence that the inversion occurs through two distinct rearrangements involving the intermediary formation of a 12,14α-cyclo-12,13-seco-5α-cholest-13(17)-ene.