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
Enantioselective Michael Addition to α,β-Unsaturated Aldehydes: Combinatorial Catalyst Preparation and Screening, Reaction Optimization, and Mechanistic Studies
作者:Ivana Fleischer、Andreas Pfaltz
DOI:10.1002/chem.200902449
日期:2010.1.4
Shortcut to chiral catalysts: An efficient combinatorial strategy based on back reaction screening by ESI‐MS allows rapid evaluation of organocatalysts for the asymmetric Michael addition to α,β‐unsaturated aldehydes (see scheme). An unexpected nonlinear effect has been observed in this reaction, resulting from a double nucleophilic–electrophilic activation mechanism involving two catalyst molecules
Ionic polymer-supported O-trimethylsilyl-α,α-diphenyl-(S)-prolinols as recoverable organocatalysts for the asymmetric Michael reactions of carbon acids with α,β-enals
作者:Oleg V. Maltsev、Alexander S. Kucherenko、Sergei G. Zlotin
DOI:10.1016/j.mencom.2011.04.011
日期:2011.5
A recyclable organocatalyst bearing O -trimethylsilyl-α,α-diphenyl-( S )-prolinol unit tagged to the imidazolium cation and poly(4-styrenesulfonate) anion in the reaction of CH-acids with α,β-enals provided the respective Michael adducts in high yields (up to 99%) and with high enantioselectivities (up to 98% ee ).
This paper reports the synthesis of prolinol-oligostytrene conjugates and their immobilization into a polystyrene matrix by using the electrospinning process. Via this approach fibers with a large surface area (fiber diameter of 1.2 µm) containing the prolinol conjugate are readily obtained. The fibers are shown to be catalytically active in a test Michael reaction. The fibrous catalyst system can readily be removed from the reaction mixture and be reused. However, a decrease of the catalyst activity was noticed upon recycling the fibrous catalyst systems.
<i>O</i>-TMS-α,α-diphenyl-(<i>S</i>)-prolinol Modified with an Ionic Liquid Moiety: A Recoverable Organocatalyst for the Asymmetric Michael Reaction between α,β-Enals and Dialkyl Malonates
作者:Oleg V. Maltsev、Alexandr S. Kucherenko、Sergei G. Zlotin
DOI:10.1002/ejoc.200900807
日期:2009.10
O-TMS-α,α-diphenyl-(S)-prolinol derivative bearing an ionicliquid fragment was synthesized for the first time and proven to be an efficient catalyst for the asymmetricMichaelreaction of aromatic α,β-unsaturated aldehydes with dialkylmalonates. The prepared catalyst can be recovered four times and used in the same reaction without a decrease in activity or a decrease in the enantioselectivity of