A Catalytic Enantioselective Michael Addition of a Simple Malonate to Prochiral α,β‐Unsaturated Ketoses and Aldehydes

Enantiomeric excesses of up to 77% ee can be achieved in the Michael addition of diisopropyl malonate to enones and enals in the presence of 5 mol % of the rubidium salt of L-proline (which contains a small amount of water) as catalyst. The absolute configurations of the products show that the nucleophile always attacks from the same side of the CO plane irrespective of the configuration of the CC bond.