Réactivité des diénamines épiconjuguées des Δ 3(9) hydrindénones—4V : Stéréochimie de la formation des δ-dicétones et de diverses attaques électrophiles

Abstract

The cross-conjugated dienamines of Δ4 4-hydrindenones react with methylvinylketone (or other electrophilic reagents such as H +, I CH 3) at the face opposite to their angular substituent at R(8). The axial attack, in the case of methylvinylketone,. leads to the isomer of the δ-diketone in which the bulky oxo-3 butyl-1 group is in an axial position. The thermodynamic equilibrium shows that this isomer is the less stable one. Therefore, kinetic control of the reaction is a steric approach control. The high degree of stereoselectivity of the reaction depends both upon the nature of the substituent R(8) = H or CH 3 and the nature of the electrophilic reagent.