to >99 % enantiomeric excess (ee) have been obtained by proline catalysis in excellent yields under experimentally simple solvent-free conditions. Efficient mixing of all the components is accomplished by applying a mechanochemical technique (ballmilling). The catalysis is air and moisture tolerant and can be performed with non-purified starting materials. Even mixtures of solely solid compounds react
Sterically and Electronically Tunable and Bifunctional Organocatalysts: Design and Application in Asymmetric Aldol Reaction of Cyclic Ketones with Aldehydes
tunable and bifunctional organocatalysts have been developed and evaluated in the direct aldolreaction of heterocyclic ketones. Catalysts with different substituents showed variablecatalytic efficiency for analogous substrates, indicating the importance of fine-tuning the strength of the hydrogen bonding in the two NH groups. The reactions all proceeded in good to high yield and with excellent enantioselectivities