A novelbifunctional organocatalyst library combining both aminocatalysis and phosphonicacid activation was used for the first time as an efficient tool for the stereoselectiveMichaeladdition of aldehydes with several aromatic nitroalkenes with good selectivities up to 95:5 dr and 93:7 er. Due to their high water solubility, the catalysts were easilyrecyclable and could be reused over several cycles
for high enantioselectivity and diastereoselectivity compared with those obtained from common trans-pyrrolidine catalysts. Not only configurational but also polymeric effects contribute to the high diastereoselectivity and enantioselectivity. Polymer catalysts were also successfully applied in a continuous-flow process. Acceleration of the reaction rate, an increase in diastereoselectivity, and an improvement
Polystyrene-Supported Diarylprolinol Ethers as Highly Efficient Organocatalysts for Michael-Type Reactions
作者:Esther Alza、Sonia Sayalero、Pinar Kasaplar、Diana Almaşi、Miquel A. Pericàs
DOI:10.1002/chem.201101730
日期:2011.10.4
addition of aldehydes to nitroolefins and of malonates or nitromethane to α,β‐unsaturated aldehydes. The combination of the catalytic unit, the triazole linker, and the polymeric matrix provides unprecedented substrate selectivity, in favor of linear, short‐chain aldehydes, when the organocatalyzed reaction proceeds by an enamine mechanism. High versatility is noted in reactions that proceed via an iminium
Some novel prolinal dithioacetal derivatives have been synthesized and applied as the organocatalysts for the direct Michaeladdition of ketones and aldehydes to nitroalkenes. High enantioselectivities and diastereoselectivities have been obtained in both organic and aqueous media (dichloromethane, water, or brine).
A Highly Selective, Polymer-Supported Organocatalyst for Michael Additions with Enzyme-Like Behavior
作者:Esther Alza、Miquelâ A. Pericà s
DOI:10.1002/adsc.200900817
日期:2009.12
A polymer-supported α,α-diarylprolinol silyl ether displays catalytic activity and enantioselectivity comparable to the best homogeneous catalysts in the Michaeladdition of aldehydes to nitroolefins. Above all, the combination of polymer backbone, triazole linker, and catalytic unit confers to it an unprecedented substrate selectivity in favor of linear, short-chain aldehydes.