water-compatible proline catalysts (4–6) derived from calixarene bearing a hydrophobic nature have been synthesised. It was found that the compound 4 was a highly efficient organocatalyst for aldol reactions occurred in the water. Under optimised reaction conditions, high yields (up to 82%), good enantioselectivities (ee up to 81%) and high diastereoselectivities (dr up to 91:9) were obtained.
[reaction: see text] Readily tunable and bifunctional L-prolinamides as novel organocatalysts have been developed, and their catalytic activities were evaluated in the direct asymmetric Aldolreactions of various aromatic aldehydes and cyclohexanone. High isolated yields (up to 94%), enantioselectivities (up to 99% ee), and anti-diastereoselectivities (up to 99:1) were obtained under the optimal conditions
Highly efficient organocatalysts for the asymmetric aldol reaction
作者:C. G. Jacoby、P. H. V. Vontobel、M. F. Bach、P. H. Schneider
DOI:10.1039/c7nj04424k
日期:——
synthetic route. The highly efficient five step methodology did not require intermediary purification and provided the compounds in high yields. The catalysts were successfully applied in the asymmetric direct aldolreaction between aromatic aldehydes and cyclic ketones in aqueous media. Aldol adducts were obtained in high yields with perfect stereoselectivities (up to >99% e.e. and >19 : 1 d.r.).
Unprecedented bifunctional enamine–metal Lewisacidcatalysts have been developed. In this bifunctional catalytic system, a tridentateligand tethered with a chiral secondary amine was designed to solve the acid–base self-quenching problem leading to catalyst inactivation. This new bifunctional enamine–metal Lewisacidcatalyst was found to catalyze aldol reactions of ketones efficiently in high yields
successfully used as a cocatalyst for L-proline catalyzed aldolreactions in the presence of water. The anticonfigured products were obtained with good yields (up to 94%), high diastereoselectivities (up to 95:5), and high enantiomeric excesses (up to 93% ee ). The successful results for catalytic efficiency of L-proline in the presence of water reveal the importance of the hydrophobic nature of cholesterol