Vollständige Dehydrierung von Sterinen und Steroiden mit Chinonen

The dehydrogenation of cholesterol, Δ^3,5 -cholestadiene, and related unsaturated compounds to afford aromatic hydrocarbons with the skeleton of 17H-cyclopenta-[a]-phenanthrene may be effected by reaction with quinones possessing high redox potentials, e.g., tetrachloro -p-benzoquinone (chloranil), 2,3 -dichloro-5,6-dicyanobenzoquinone (DDQ), etc., in high-boiling solvents such as p-xylene and anisole at reflux temperature. The reaction proceeds stepwise. Angular methyl groups present in the steroid molecule either migrate to the 1,4, or 17 positions, or are eliminated. This dehydrogenation reaction may also be applied to seco-steroids such as vitamin D. With suitable steroids, Diels-Alder additon of the quinone to partially dehydrogenated intermediates possessing a cis-1,3-diene group is the predominant reaction; the addition products are further dehydrogenated to polycyclic aromatic compounds. In the case of some estrone derivatives and related compounds, the dehydrogenation reaction involves opening of ring D. The reaction may serve to prepare certain aromatic compounds, the synthesis of which is difficult by other methods.