Controlling the alpha/gamma-Reactivity of Vinylogous Ketone Enolates in Organocatalytic Enantioselective Michael Reactions

摘要

The first regio-, diastereo-, and enantioselective direct Michael reaction of beta,gamma-unsaturated ketones with nitroolefins is enabled by Bronsted base/hydrogen-bonding bifunctional catalysis. A squaramide-substituted tertiary amine catalyzes the reaction of a broad range of beta,gamma-unsaturated ketones to proceed at the alpha-site exclusively, giving rise to adducts with two consecutive tertiary carbon stereocenters in diastereomeric ratios of up to > 20:1 and enantioselectivities generally in the 90-98 ee range.