Sequential Reactions of Michael Addition and Peterson Condensation of 1-Silylvinyl Ketones with Grignard Reagents: Study of Stereoselectivity

Abstract 1-Silylvinyl ketones undergo smooth Michael addition with Grignard reagents generating magnesium enolates which are then trapped with benzaldehyde to give E- and Z-isomers of enones after Peterson condensation. (E)-Olefins become major products under a thermodynamic control when the condensation with benzaldehyde is carried out at room temperature in diethyl ether, while Z-isomers are more favored as kinetically controlled products at −78 °C in THF. Reaction mechanism is briefly discussed.