Sterically and electronically tunable and bifunctional organocatalysts: design and application in asymmetric aldol reaction of cyclic ketones with aldehydes.J Org Chem. 2006 Oct 13; 71(21):8198-202.JO
Sterically and electronically tunable and bifunctional organocatalysts have been developed and evaluated in the direct aldol reaction of heterocyclic ketones. Catalysts with different substituents showed variable catalytic 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 ranging from 90% to >99% ee. In most cases, high diastereoselectivities ranging from 96/4 to 99/1 were obtained for the anti aldol adduct.