Chiral organoaluminum complex 1 efficiently catalyzed the asymmetric hetero-ene reaction of commercially available 2-methoxypropene (2) with aldehydes under mild conditions to give the corresponding β-hydroxymethyl ketones 3 in good to excellent chemical yields with high enantiomeric excesses. The asymmetriccatalysis of 1 was further applied to the carbonyl addition of methallylsilanes, where exclusive
Rational Combination of Two Privileged Chiral Backbones: Highly Efficient Organocatalysts for Asymmetric Direct Aldol Reactions between Aromatic Aldehydes and Acylic Ketones
A new class of organocatalysts has been designed by rational combination of proline with cinchona alkaloids. The chiral amine 3a, prepared from l-proline and cinchonidine, has been found to be an efficient catalyst for the directaldolreactions of acetone or 2-butanone with a wide range of aldehydes (up to 98% ee). The cinchonidine backbone is essential to the reaction efficiency and enantioselectivity
Tandem Catalysis by Lipase in a Vinyl Acetate-Mediated Cross-Aldol Reaction
作者:Manjeet Kumar、Bhahwal A. Shah、Subhash C. Taneja
DOI:10.1002/adsc.201000980
日期:2011.5
The lipase Novozym435 (0.6% w/w) was used in tandem with organocatalysts in a first vinyl/isopropenyl acetate‐mediated aldol reaction. The reaction was facilitated through the lipase‐catalyzed in situ generation of acetaldehyde/acetone. The important features of the present methodology include the mild and facile reaction conditions, regenerability of the lipase, comparatively high yields and minimal
Unexpected Beneficial Effect of ortho-Substituents on the (S)-Proline-Catalyzed Asymmetric Aldol Reaction of Acetone with Aromatic Aldehydes
作者:Benjamin List、Alberto Martínez、Manuel van Gemmeren
DOI:10.1055/s-0033-1340920
日期:——
An intriguing effect of electronegative 2,6-substituents on the stereochemical outcome of (S) -proline-catalyzed aldol reactions between benzaldehyde derivatives and acetone is reported. Remarkably high enantioselectivities can be achieved with such substrates.
Thiazolidine-based organocatalysts for a highly enantioselective direct aldol reaction
作者:Raoní S. Rambo、Paulo H. Schneider
DOI:10.1016/j.tetasy.2010.07.028
日期:2010.9
exhibits the highest catalytic performance working in an aqueous medium. It catalyzed the directcatalyticasymmetric intermolecular aldolreaction between unmodifiedketones and an aldehyde with excellent stereocontrol and furnished the corresponding aldol products in up to 99% ee. Compound 3a also showed excellent asymmetriccatalytic activity in the asymmetric Michael reaction (up to 99% ee).