Enantioselective Michael Addition to α,β‐Unsaturated Aldehydes: Combinatorial Catalyst Preparation and Screening, Reaction Optimization, and Mechanistic Studies

Shortcut to chiral catalysts: An efficient combinatorial strategy based on back reaction screening by ESI‐MS allows rapid evaluation of organocatalysts for the asymmetric Michael addition to α,β‐unsaturated aldehydes (see scheme). An unexpected nonlinear effect has been observed in this reaction, resulting from a double nucleophilic–electrophilic activation mechanism involving two catalyst molecules.