抄録
The 1H-and 13C-nuclear magnetic resonance spectra of progesterone (VII) in 97% H2SO4 indicated the formation of a dication (VIII), which was transformed to another dication χ-301 (X) consisting of a hydroxyalkenyl cation moiety in ring A and a cyclopentenyl one in ring D, when the acid solution was heated at 80°C for 2h. At a reduced acid-strength of the reaction system, X was converted to the hydroxyalkatrienyl cation χ-482 (XIV) through an acid-base equilibrium on the one hand, and to the hydroxyalkatetraenyl cation χ-600 (XV) by an oxidative process on the other. The structures of these cations were confirmed by isolating the corresponding conjugate bases, 17ζ-isopropyl-18-nor-13ζ-androsta-4, 6, 8 (14)-trien-3-one (XII) and 17-isopropyl-18-norandrosta-4, 6, 8 (14), 13 (17)-tetraen-3-one (XIII), from the colored solutions. The pKa values of the cations XIV and XV were-4.6 and -3.8, respectively. On the basis of these results, a mechanism is proposed for the title reaction.
