ADDITION REGIOSELECTIVE D'ENOLATES DE CETONES AUX α-ENONES INFLUENCE DES FACTEURS STERIQUES SUR L'ORIENTATION ET LA REVERSIBILITE DES REACTIONS

Article abstract of DOI:10.1016/0040-4020(84)85094-2

Regio and stereochemistry in the addition of preformed magnesium and lithium ketone enolates (1 to 8) to α-enones (10 and 11) have been examined.When the substitution degree of the enolate is increased the formation of δ-diketone is favoured; neverthless a good efficiency in the synthesis of the γ-ethylenic β-ketols (1-2 addition) is obtained via bromomagnesium enolates (EMgX) under kinetic conditions.Lithium enolate (ELi) and, chiefly magnesium bienolate (E2Mg) give preferentially the Michael addition.Reversibility from 1-2 to 1-4 addition is commonly observed but the stereochemistry, if any, of the diastereoisomeric δ-diketones may be quite different when using EMgBr or E2Mg as starting enolates.