Catalytic Asymmetric Heterodimerization of Ketenes
摘要:
In this Communication we describe an unprecedented catalytic asymmetric heterodimerization of ketenes of wide substrate scope. The alkaloid-catalyzed method provides access to ketene heterodimer beta-lactones and allows even two different monosubstituted ketenes to be cross-dimerized, with excellent enantioselectivity (17 examples with >= 90% ee) and excellent heterodimer regioselectivity observed in all cases.
GENERAL METHOD FOR INCREASING STEREOSELECTIVITY IN STEREOSELECTIVE REACTIONS
申请人:Meyer Matthew P.
公开号:US20090163741A1
公开(公告)日:2009-06-25
This invention is directed to a method of performing a stereoselective reaction without use of a solvent comprising contacting a reactant with a chiral reagent under sonication conditions to form an excess of an enantiomer.
Direct catalytic asymmetric cross-aldol reactions in ionic liquid media
作者:Armando Córdova
DOI:10.1016/j.tetlet.2004.03.080
日期:2004.5
Enantioselective proline-catalyzed direct asymmetric cross-aldol reactions with aldehydes were performed in ionicliquid 1-n-butyl-3-methylimidazolium hexafluorophosphate media, which simplified product isolation and catalyst recycling, affording 3-hydroxy aldehydes in high yield with excellent stereoselectivity. In addition, the enhanced reactivity of the asymmetric cross-aldol reactions in ionic
reactions enabled the asymmetric synthesis of deoxysugars with >99 % ee. In addition, the direct amino acid catalyzed C(2)+C(2)+C(2) methodology is a new entry for the short, highly enantioselective denovosynthesis of carbohydrate derivatives, isotope-labeled sugars, and polyketide natural products. The one-pot asymmetric denovo syntheses of deoxy and polyketide carbohydrates involved a novel dynamic kinetic
[EN] DIRECT, ENANTIOSELECTIVE ALDOL COUPLING OF ALDEHYDES USING CHIRAL ORGANIC CATALYSTS<br/>[FR] COUPLAGE ALDOLIQUE ENANTIOSELECTIF DIRECT D'ALDEHYDES A L'AIDE DE CATALYSEURS ORGANIQUES CHIRAUX
申请人:CALIFORNIA INST OF TECHN
公开号:WO2003089396A1
公开(公告)日:2003-10-30
Nonmetallic, chiral organic catalysts are used to catalyze an enantioselective aldol coupling reaction between aldehyde substrates. The reaction may be carried out with a single enolizable aldehyde, resulting in dimerization to give a β-hydroxy aldehyde, or trimerization to give a dihydroxy tetrahydropyran. The reaction may also conducted with an enolizable aldehyde and a second aldehyde, which may or may not be enolizable, so that the coupling is a cross-aldol reaction in which the a-carbon of the enolizable aldehyde adds to the carbonyl carbon of the second aldehyde in an enantioselective fashion. Reaction systems composed of at least one enolizable aldehyde, an optional additional aldehyde, and the nonmetallic chiral organic catalyst are also provided, as are methods of implementing the enantioselective aldol reaction in the synthesis of sugars.
Enantioselective synthesis of prelactone B using a proline-catalyzed crossed-aldol reaction
作者:Petri M. Pihko、Anniina Erkkilä
DOI:10.1016/j.tetlet.2003.08.060
日期:2003.10
Catalytic enantioselective synthesis of prelactone B has been achieved in only four steps. A direct proline-catalyzed aldehyde–aldehyde aldol reaction is employed as the sole source of chirality.