Matches in DBpedia 2015-10 for { <http://dbpedia.org/resource/Hajos–Parrish–Eder–Sauer–Wiechert_reaction> ?p ?o }
Showing triples 1 to 85 of
85
with 100 triples per page.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction abstract "The Hajos–Parrish–Eder–Sauer–Wiechert reaction in organic chemistry is a proline catalysed asymmetric aldol reaction. The reaction is named after its principal investigators, Zoltan Hajos others, from Hoffmann-La Roche and Schering AG. Discovered in the 1970s the original Hajos-Parrish catalytic procedure - shown in the reaction equation - leading to the optically active bicyclic ketol as well as the Eder-Sauer-Wiechert modification leading to the optically active enedione through the loss of water from the ketol paved the way of asymmetric organocatalysis. It has been used extensively as a tool in the synthesis of steroids and other enantiomerically pure molecules.400pxFigure 1.In the original reaction shown in Figure 1. naturally occurring chiral proline is the chiral catalyst in an Aldol reaction. The starting material is an achiral triketone and it requires just 3% of proline to obtain the reaction product, a ketol in 93% enantiomeric excess. As shown above, Hajos and Parrish worked at ambient temperature in dimethylformamide (DMF) solvent using a catalytic amount (3% molar equiv.) of (S)-(−)-proline enabling them to isolate the optically active intermediate bicyclic ketol. Thus, they described the first use of proline in a catalytic asymmetric aldol reaction.The Schering group worked under non biological conditions using (S)-Proline (47 mol%), 1N perchloric acid, in acetonitrile at 80 °C. Hence, they could not isolate the Hajos, Parrish intermediate bicyclic ketol but instead the condensation product (7aS)-7a-methyl-2,3,6,7-tetrahdroindol-1,5-dione through the loss of water. Thirty-seven years later a new group at Schering AG published the continuation of the earlier Schering work [3]. Instead of the aforementioned non biological conditions the new group used the Hajos-Parrish catalytic procedure. Thus, they could isolate the optically active 6,5-bicyclic ketol described so far only in the Hajos-Parrish publications [1],[2] .Hajos and Parrish investigated further the exact configuration of the above cis-fused-7a-methyl- 6,5-bicyclic-ketol by circular dichroism, and these results were confirmed by a single-crystal X-ray diffraction study. The centro symmetrical crystal of the corresponding racemic ketol without a heavy atom label has been obtained by the use of racemic proline. It showed by X-ray diffraction an axial orientation of the angular methyl group and an equatorial orientation of the hydroxyl group in the chair conformer of the six-membered ring. This is in good agreement with the crystal structure of the CD-ring of digitoxigenin. The structure of this ketol and its ethyl homologue are shown as follows.400pxHajos-Parrish ketolsSimilar studies of the 7a-ethyl-homologue showed that the ethyl bicycic ketol existed in a cis conformation in which the 7a-ethyl group is equatorially oriented and the hydroxyl group is axially oriented in the chair form of the six-membered ring as shown above. The reason for a preference for this conformation could be enhanced 1,3-diaxial interaction in the other cis conformer between the angular ethyl group and the axial hydrogens at C-4 and C-6 in the six membered ring.In a 2000 study the Barbas group found that intermolecular aldol additions (those between ketones and aldehydes) are also possible albeit with use of considerably more proline:Aldol Barbas 2000The authors noted the similarity of proline, the aldolase antibodies they had created and natural aldolase enzymes aldolase A all of which operate through an enamine intermediate. In this reaction the large concentration of acetone (one of the two reactants) suppresses various possible side-reactions: reaction of the ketone with proline to an oxazolidinone and reaction of the aldehyde with proline to an azomethine ylide.Notz and List went on to expand the utility of this reaction to the synthesis of 1,2-diols:Synthesis of diols Notz 2000In their full account of their 2000 Communication, the group revealed that proline together with the thiazolium salt 5,5-dimethyl thiazolidinium-4-carboxylate were found to be the most effective catalysts among a large group of amines, while catalysis with (S)-1-(2-pyrrolidinylmethyl)-pyrrolidine salts formed the basis for the development of diamine organocatalysts that have proven effective in a wide variety or organocatalytic reactions.The asymmetric synthesis of the Wieland-Miescher ketone (1985) is another intramolecular reaction also based on proline, that was explored by the Barbas group in 2000. In this study the Barbas group demonstrated for the first time that proline can catalyze the cascade Michael-aldol reaction through combined iminium-enamine catalysis. This work is significant because despite the 30-year history and application of the Hajos-Parrish reaction in industry, the triketone substrate for this reaction had always been synthesized in a discrete independent step, demonstrating that there was a fundamental lack of understanding of the chemical mechanism of this reaction. The Barbas group had reported the aldolase antibody catalyzed iminium-enamine Robinson annulation in their 1997 study that marked the beginning of their studies in the area now called organocatalysis. In a report published in 2002 Carlos F. Barbas III said: "Work in the 1970s on proline-catalyzed intramolecular aldol addition reactions by synthetic organic chemists Zoltan G. Hajos and David R. Parrish of the chemical research department at Hoffmann-La Roche, Nutley, N.J., inspired us to look more closely at parallels between small-molecule catalysts and enzymes".In 2002 the Macmillan group was the first to demonstrate the proline catalyzed Aldol reaction between different aldehydes. This reaction is unusual because in general aldehydes will self-condense.Aldol Macmillan 2002The organocatalytic intermolecular aldol reaction is now known as the Barbas-List Aldol reaction.".
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction thumbnail Organocatalytic1.svg?width=300.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageID "9363304".
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageLength "21422".
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageOutDegree "60".
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageRevisionID "680532199".
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink 2-Oxazolidone.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Acetone.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Acetonitrile.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Aldehyde.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Aldol_reaction.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Aldolase_A.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Asymmetric_synthesis.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Azomethine_ylide.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Cahn–Ingold–Prelog_priority_rules.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Category:Addition_reactions.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Category:Name_reactions.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Chemical_kinetics.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Chloral.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Digitoxigenin.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Dimethyl_sulfoxide.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Dimethylformamide.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Enamine.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Enantiomeric_excess.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Enantioselective_synthesis.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Equilibrium_constant.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Hemiaminal.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Hoffmann-La_Roche.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Hydrogen_bond.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Hydrogen_bonding.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Intermolecular.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Intermolecular_force.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Intramolecular_reaction.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Isotopic_labeling.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Ketone.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Nitrosobenzene.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Organic_chemistry.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Organocatalysis.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Oxazolidinone.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Perchloric_acid.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Proline.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Prolinol.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Propanal.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Propionaldehyde.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Re_face.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Reaction_kinetics.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Reaction_mechanism.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Schering_AG.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Stereoselectivity.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Steroid.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Steroids.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Thiazole.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Thiazolium_salt.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Transition_state.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Wieland-Miescher_ketone.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Wieland–Miescher_ketone.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Zimmerman-Traxler_model.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink Zoltan_Hajos.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink File:AldolBarbas2000.svg.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink File:AldolList2001Diol.svg.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink File:AldolMacmillan2002.svg.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink File:AldolMechanismList2000.svg.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink File:AldolTriketoneMechanisms.svg.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink File:C.T.Wong-Tet.Let.-(50)2009-811.svg.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink File:ChloralAldolSeebach2007.svg.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink File:Hajos-Parrish-ketols-2.svg.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink File:Organocatalytic1.svg.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink File:OxazolidinoneFormationByreactionOfKetoneWithProline.svg.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLink File:ProlineCatalysedAminoxylation.svg.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageWikiLinkText "Hajos–Parrish–Eder–Sauer–Wiechert reaction".
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction hasPhotoCollection Hajos–Parrish–Eder–Sauer–Wiechert_reaction.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wikiPageUsesTemplate Template:Reflist.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction subject Category:Addition_reactions.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction subject Category:Name_reactions.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction comment "The Hajos–Parrish–Eder–Sauer–Wiechert reaction in organic chemistry is a proline catalysed asymmetric aldol reaction. The reaction is named after its principal investigators, Zoltan Hajos others, from Hoffmann-La Roche and Schering AG.".
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction label "Hajos–Parrish–Eder–Sauer–Wiechert reaction".
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction sameAs Hajos-Parrish-Eder-Sauer-Wiechert-Reaktion.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction sameAs Hajos–Parrish–Eder–Sauer–Wiechert-reakció.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction sameAs m.03gqbrs.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction sameAs Q725232.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction sameAs Q725232.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction sameAs Hajos–Parrish–Eder–Sauer–Wiechert反应.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction wasDerivedFrom Hajos–Parrish–Eder–Sauer–Wiechert_reaction?oldid=680532199.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction depiction Organocatalytic1.svg.
- Hajos–Parrish–Eder–Sauer–Wiechert_reaction isPrimaryTopicOf Hajos–Parrish–Eder–Sauer–Wiechert_reaction.