Origin of the Enantioselectivity in Organocatalytic Michael Additions of beta-Ketoamides to alpha,beta-Unsaturated Carbonyls: A Combined Experimental, Spectroscopic and Theoretical Study

摘要

The organocatalytic enantioselective conjugate addition of secondary beta-ketoamides to alpha,beta-unsaturated carbonyl compounds is reported. Use of bifunctional Takemoto's thiourea catalyst allows enantiocontrol of the reaction leading either to simple Michael adducts or spirocyclic aminals in up to 99 ee. The origin of the enantioselectivity has been rationalised based on combined DFT calculations and kinetic analysis. This study provides a deeper understanding of the reaction mechanism, which involves a predominant role of the secondary amide proton, and clarifies the complex interactions occurring between substrates and the catalyst.