Applications of high-potential quinones. Part VI. Stereoelectronic effects in the dehydrogenation of neoergosterols

Abstract

Neoergosterols undergo rapid hydrogen transfer with dichlorodicyanobenzoquinone at room temperature to give Δ¹⁴-derivatives in high yield. Further dehydrogenation also occurs in ring D, giving Δ^14,16-neoergosterols. Stereoelectronic effects governing the rate and specificity of these oxidations are discussed. In the mass spectra of the Δ^14,16-sterols, the preferred mode of side-chain fragmentation involves transfer of only one hydrogen atom from the nucleus.