- Synthesis of optically pure 3R-methylcyclopentan-1-one from L-(-)-menthol
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Synthesis of optically pure 3R-methylcyclopentan-1-one using in the key step Dieckmann cyclization of diisopropyl 3R-methylhexan-1,6-dioate, which is accessible from L-(-)-menthol, was proposed. 2005 Springer Science+Business Media, Inc.
- Ishmuratov,Yakovleva,Ganieva,Gareeva,Muslukhov,Tolstikov
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- A robust and stereocomplementary panel of ene-reductase variants for gram-scale asymmetric hydrogenation
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We report an engineered panel of ene-reductases (ERs) from Thermus scotoductus SA-01 (TsER) that combines control over facial selectivity in the reduction of electron deficient C[dbnd]C double bonds with thermostability (up to 70 °C), organic solvent tolerance (up to 40 % v/v) and a broad substrate scope (23 compounds, three new to literature). Substrate acceptance and facial selectivity of 3-methylcyclohexenone was rationalized by crystallisation of TsER C25D/I67T and in silico docking. The TsER variant panel shows excellent enantiomeric excess (ee) and yields during bi-phasic preparative scale synthesis, with isolated yield of up to 93 % for 2R,5S-dihydrocarvone (3.6 g). Turnover frequencies (TOF) of approximately 40 000 h?1 were achieved, which are comparable to rates in hetero- and homogeneous metal catalysed hydrogenations. Preliminary batch reactions also demonstrated the reusability of the reaction system by consecutively removing the organic phase (n-pentane) for product removal and replacing with fresh substrate. Four consecutive batches yielded ca. 27 g L?1 R-levodione from a 45 mL aqueous reaction, containing less than 17 mg (10 μM) enzyme and the reaction only stopping because of acidification. The TsER variant panel provides a robust, highly active and stereocomplementary base for further exploitation as a tool in preparative organic synthesis.
- Nett, Nathalie,Duewel, Sabine,Schmermund, Luca,Benary, Gerrit E.,Ranaghan, Kara,Mulholland, Adrian,Opperman, Diederik J.,Hoebenreich, Sabrina
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- Counterion Enhanced Organocatalysis: A Novel Approach for the Asymmetric Transfer Hydrogenation of Enones
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We present a novel strategy for organocatalytic transfer hydrogenations relying on an ion-paired catalyst of natural l-amino acids as main source of chirality in combination with racemic, atropisomeric phosphoric acids as counteranion. The combination of a chiral cation with a structurally flexible anion resulted in a novel chiral framework for asymmetric transfer hydrogenations with enhanced selectivity through synergistic effects. The optimized catalytic system, in combination with a Hantzsch ester as hydrogen source for biomimetic transfer hydrogenation, enabled high enantioselectivity and excellent yields for a series of α,β-unsaturated cyclohexenones under mild conditions. Moreover, owing to the use of readily available and chiral pool-derived building blocks, it could be prepared in a straightforward and significantly cheaper way compared to the current state of the art.
- Scharinger, Fabian,Márk Pálv?lgyi, ádám,Zeindlhofer, Veronika,Schnürch, Michael,Schr?der, Christian,Bica-Schr?der, Katharina
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p. 3776 - 3782
(2020/06/22)
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- Enantio- A nd regioselective: Ene-reductions using F420H2-dependent enzymes
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In the past decade it has become clear that many microbes harbor enzymes that employ an unusual flavin cofactor, the F420 deazaflavin cofactor. Herein we show that F420-dependent reductases (FDRs) can successfully perform enantio-, regio- A nd chemoselective ene-reductions. For the first time, we have demonstrated that F420H2-driven reductases can be used as biocatalysts for the reduction of α,β-unsaturated ketones and aldehydes with good conversions (>99%) and excellent regioselectivities and enantiomeric excesses (>99% ee). Noteworthily, FDRs typically display an opposite enantioselectivity when compared to the well established FMN-dependent Old Yellow Enzymes (OYEs).
- Mathew, Sam,Trajkovic, Milos,Kumar, Hemant,Nguyen, Quoc-Thai,Fraaije, Marco W.
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supporting information
p. 11208 - 11211
(2018/10/15)
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- Imido-P(v) trianion supported enantiopure neutral tetrahedral Pd(II) cages
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Charge-neutral chiral hosts are attractive due to their ability to recognize a wide range of guest functionalities and support enantioselective processes. However, reports on such charge-neutral cages are very scarce in the literature. Here, we report an enantiomeric pair of tetrahedral Pd(ii) cages built from chiral tris(imido)phosphate trianions and oxalate linkers, which exhibit enantioselective separation capabilities for epichlorohydrin, β-butyrolactone, and 3-methyl- and 3-ethyl cyclopentanone.
- Rajasekar, Prabhakaran,Pandey, Swechchha,Paithankar, Harshad,Chugh, Jeetender,Steiner, Alexander,Boomishankar, Ramamoorthy
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supporting information
p. 1873 - 1876
(2018/02/23)
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- Enantioselective copper-catalyzed 1,4-addition of dialkylzincs to enones followed by trapping with allyl iodide derivatives
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Enantioselective copper-catalyzed 1,4-addition of dialkylzincs to enones proceeded in the presence of 0.1 mol% of Cu(OTf)2 and 0.25 mol% of an N,N,P-ligand containing a quinoline moiety to afford the corresponding conjugated adducts in 99%ee. The intermediate zinc enolates were trapped with substituted allyl iodides to give disubstituted ketones with high diastereoselectivity and enantioselectivity.
- Kawamura, Kenjiro,Fukuzawa, Hitomi,Hayashi, Masahiko
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experimental part
p. 640 - 647
(2011/08/06)
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- Copper-catalyzed asymmetric 1,4-conjugate addition of dialkylzinc to enones
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Asymmetric 1,4-conjugation addition of dialkylzinc (diethylzinc and dimethylzinc) to cyclic enones, chalcone and nitroalkenes was achieved by a 25 mol% (R)-6,6'-Br2-BINOL(1f), 25 mol% CuSPh and 100 mol% dicyclohexylmethylamin(Cy2NMe) catalyst system. The Cu(I) catalyst system enables the cyclic enone, chalcone and nitroalkene generality with high enantioselectivity (up to84%ee) and isolated yield (up to 94%) under mild reaction conditions.
- Gou, Shaohua,Ye, Zhongbin,Shi, Leiting,Qing, Dayong,Zhang, Wen,Wang, Yuliang
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experimental part
p. 517 - 522
(2010/10/18)
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- Synthesis and AChE inhibitory activity of new chiral tetrahydroacridine analogues from terpenic cyclanones
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This work describes the enantioselective synthesis of a new series of terpenic chiral 9-aminotetrahydroacridine analogues. Several chiral ketones were synthesized from natural monoterpenes in an optically active form and subjected to the cyclodehydration reactions with anthranilonitrile in the presence of BF3·Et2O as catalyst. The 9-aminotetrahydroacridine analogues were tested as acetylcholinesterase (AChE) inhibitors. Based on qualitative structure-activity relationship some trends are suggested.
- Santos Pisoni, Diego dos,Sobieski da Costa, Jessé,Gamba, Douglas,Petzhold, Cesar Liberato,César de Amorim Borges, Antonio,Ceschi, Marco Antonio,Lunardi, Paula,Saraiva Gon?alves, Carlos Alberto
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scheme or table
p. 526 - 535
(2010/04/06)
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- Directed evolution of an enantioselective enoate-reductase: Testing the utility of iterative saturation mutagenesis
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Directed evolution utilizing iterative saturation mutagenesis (ISM) has been applied to the old yellow enzyme homologue YqjM in the quest to broaden its substrate scope, while controlling the enantioselectivity in the bioreduction of a set of substituted cyclopentenone and cyclohexenone derivatives. Guided by the known crystal structure of YqjM, 20 residues were selected as sites for saturation mutagenesis, a pooling strategy based on the method of Phizicky [M. R. Martzen, S. M. McCraith, S. L. Spinelli, F. M. Torres, S. Fields, E. J. Grayhack, E. M. Phizicky, Science 1999, 286, 1153-1155] being used in the GC screening process. The genes of some of the hits were subsequently employed as templates for randomization experiments at the other putative hot spots. Both (R)-and (S)-selective variants were evolved using 3-methylcyclohexenone as the model substrate in the asymmetric bioreduction of the olefinic functionality, only small mutant libraries and thus minimal screening effort being necessary. Some of the best mutants also proved to be excellent catalysts when testing other prochiral substrates without resorting to additional mutagenesis/screening experiments. Thus, the results constitute an important step forward in generalizing the utility of ISM as an efficient method in laboratory evolution of enzymes as catalysts in organic chemistry.
- Bougioukou, J. Despina,Kille, Sabrina,Taglieber, Andreas,Reetz, Manfredt.
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scheme or table
p. 3287 - 3305
(2010/04/30)
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- Asymmetric catalysis: Resin-bound hydroxyprolylthreonine derivatives in enamine-mediated reactions
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Control of stereochemistry is achieved using two TentaGel-bound di-tert-butoxyprotected hydroxyprolyl-threonine catalysts (see picture, sphere represents TentaGel). These catalysts mediate asymmetric tandem enamine/Michael reactions with high enantioselectivity and complete diastereoselectivity; the choice of catalyst depends on the desired absolute configuration. (Chemical Equation Presented).
- Carpenter, Richard D.,Fettinger, James C.,Lam, Kit S.,Kurth, Mark J.
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supporting information; experimental part
p. 6407 - 6410
(2009/03/11)
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- Asymmetric bioreduction of C=C bonds using enoate reductases OPR1, OPR3 and YqjM: Enzyme-based stereocontrol
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Three cloned enoate reductases from the "old yellow enzyme" family of flavoproteins were investigated in the asymmetric bioreduction of activated alkenes. 12-Oxophytodienoate reductase isoenzymes OPR1 and OPR3 from Lycopersicon esculentum (tomato), and YqjM from Bacillus subtilis displayed a remarkably broad substrate spectrum by reducing α,β-unsaturated aldehydes, ketones, maleimides and nitroalkenes. The reaction proceeded with absolute chemoselectivity-only the conjugated C=C bond was reduced, while isolated olefins and carbonyl groups remained intact-with excellent stereoselectivities (ees up to >99%). Upon reduction of a nitroalkene, the stereochemical outcome could be determined via choice of the appropriate enzyme (OPR1 versus OPR3 or YqjM), which furnished the corresponding enantiomeric nitroalkanes in excellent ee. Molecular modelling suggests that this "enzyme-based stereocontrol" is caused by subtle differences within the active site geometries.
- Hall, Melanie,Stueckler, Clemens,Ehammer, Heidemarie,Pointner, Eva,Oberdorfer, Gustav,Gruber, Karl,Hauer, Bernard,Stuermer, Rainer,Kroutil, Wolfgang,Macheroux, Peter,Faber, Kurt
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experimental part
p. 411 - 418
(2009/04/10)
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- Enantioselective hydrogenation of enones with a hydroformylation catalyst
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Use of a typical rhodium precatalyst for hydroformylation results in the enantioselective hydrogenation of cyclic enones with up to 90% ee. Extensive screening of chiral ligands reveals the simple ligand Chiraphos as the best ligand, so far. The hydrogenation shows high chemoselectivity. Exclusive formation of saturated, chiral b-branched ketones is observed. It is proposed that the catalyst follows a frustrated hydroformylation pathway ("monohydride-based mechanism") and differs by that from the classical cationic Schrock-Osborn type rhodium precatalysts ("dihydride-based mechanism") for enantioselective hydrogenation. The catalyst operates under neat conditions and is easily recyclable by simply distilling off the reaction mixture and treatment with syn gas prior to hydrogenation.
- Scheuermann Nee Taylor, Caroline J.,Jaekel, Christoph
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supporting information; experimental part
p. 2708 - 2714
(2009/10/06)
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- Hydride reduction of alpha, beta-unsaturated carbonyl compounds using chiral organic catalysts
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Nonmetallic, chiral organic catalysts are used to catalyze the 1,4-hydride reduction of an α,β-unsaturated carbonyl compound. The α,β-unsaturated carbonyl compound may be an aldehyde or cyclic ketone, and the hydride donor may be a dihydropyridine. The reaction is enantioselective, and proceeds with a variety of hydride donors, catalysts, and substrates. The invention also provides compositions effective in carrying out the 1,4-hydride addition of α,β-unsaturated carbonyl compounds.
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Page/Page column 22-23
(2008/06/13)
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- METHOD FOR THE PRODUCTION OF OPTICALLY ACTIVE CARBONYL COMPOUNDS
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The invention relates to a method for the production of optically active carbonyl compounds by means of asymmetrical hydrogenation of α,?-unsaturated carbonyl compounds in the presence of optically active transition metal catalysts which are soluble in the reaction mixture, said catalysts comprising at least one carbon monoxide ligand. The invention specifically relates to a method for the production of optically active aldehydes or ketones, in particular citronellal by means of the asymmetrical hydrogenation of the correspondingly optically active α,?-unsaturated aldehydes or ketones.
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Page/Page column 25-26
(2008/06/13)
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- Organocatalytic transfer hydrogenation of cyclic enones
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The first enantioselective organocatalytic transfer hydrogenation of cyclic enones has been accomplished. The use of iminium catalysis has provided a new organocatalytic strategy for the enantioselective reduction of β,β-substituted α,β-unsaturated cycloalkenones, to generate β-stereogenic cyclic ketones. The use of imidazolidinone 4 as the asymmetric catalyst has been found to mediate the hydrogenation of a large class of enone substrates with tert-butyl Hantzsch ester serving as an inexpensive source of hydrogen. The capacity of catalyst 4 to enable enantioselective transfer hydrogenation of cycloalkenones has been extended to five-, six-, and seven-membered ring systems. The sense of asymmetric induction is in complete accord with the stereochemical model first reported in conjunction with the use of catalyst 4 for enantioselective ketone Diels-Alder reactions. Copyright
- Tuttle, Jamison B.,Ouellet, Stephane G.,MacMillan, David W. C.
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p. 12662 - 12663
(2008/02/05)
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- Highly enantioselective copper-catalyzed 1,4-conjugate addition of diethylzinc to cyclic enones and αβ-unsaturated lactones
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A significant improvement in enantioselectivity has been achieved in the 1,4-additions of diethylzinc to 2-cyclopentenone, 2-cyclohexenone and 5,6-hydro-2H-pyran-2-one (up to 93%, 98% and 94% ee, respectively) by using a chiral diphosphite-copper catalyst under suitable reaction conditions.
- Liang, Liang,Yan, Ming,Li, Yue-Ming,Chan, Albert S.C.
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p. 2575 - 2578
(2007/10/03)
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- Ketonic decarboxylation catalysed by weak bases and its application to an optically pure substrate
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Ketonic decarboxylation is a very old reaction that transforms two carboxylic acids into a ketone or a dicarboxylic acid into a cyclic ketone, in particular adipic acid into cyclopentanone. Herein it is reported that catalytic amounts of weak bases such as sodium carbonate can carry out this reaction selectively. This is in accordance with a mechanism involving decarboxylation and nucleophilic attack at a second carboxyl group. The reaction can be employed in asymmetric syntheses since the stereogenic centres in the β-positions retain their stereochemistry. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Renz, Michael,Corma, Avelino
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p. 2036 - 2039
(2007/10/03)
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- Cyclic ketones, their preparation and their use in the synthesis of amino acids
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A method is provided for making an enantiomerically pure of the formula: in which R and R′ represent C1?C10 alkyl, C2?C10 alkenyl or C3?C10 cycloalkyl and the wedges signify (S)- or (R)-stereochemistry, the substituents in compound (II) being trans. Conjugate addition is carried out between an organometallic nucleophile that provides a group R as defined above and (R)-4-acetoxycyclopent-2-en-1-one, (S)-4-acetoxycyclopent-2-en-1-one or a similar compound in which acetoxy is replaced by another leaving group to give, e.g. in the case of the acetoxy compound, a trans 3,4-disubstituted addition product of formula III or IV; The acetyl group is eliminated from the addition product to give an (R)- or (S)-4-alkyl or 4-alkenyl cyclopent-2-en-1-one the compound of formula is then to be hydrogenated to give a cyclopentanone of formula (I) or conjugate addition of a second organometallic nucleophile that provides a group R′ as defined above to the compound of the above formula may be carried out to give a trans 3,4-disubstituted addition product of formula (II). One of the above compounds may be converted e.g. via an intermediate (XV)-(XVIII) (in which the substituents R and R′ and the wedges have the meanings indicated above) to a gabapentin analogue of one of the formulae shown below: in which the substituents R and R′ and the wedges also have the meanings indicated above.
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- Highly Enantioselective 1,4-Addition of Diorganozinc Reagents to Cyclic Enones Using Chiral Diphosphite Ligands Derived from H8-Binaphthol
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(Matrix Presented) High enantioselectivities have been achieved in the 1,4-addition of dialkylzincs to 2-cyclopentenone, 2-cyclohexenone, and 2-cycloheptenone with ee values up to 99% by using chiral aryl diphosphite ligands derived from H8-binaphthol.
- Liang, Liang,Au-Yeung, Terry T.-L.,Chan, Albert S. C.
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p. 3799 - 3801
(2007/10/03)
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- Asymmetric hydrogenation of substituted 2-pyrones
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Various substituted 2-pyrones have been hydrogenated with high enantioselectivity (up to 97% ee) to the corresponding 5,6-dihydropyrones using cationic ruthenium catalysts containing the (6,6'-dimethoxybiphenyl- 2,2'diyl)bis[3,5-di(tert-butyl)phenylphosphine] ligand. When substituents at position 3 are absent, 5,6-dihydropyrones are further hydrogenated to the fully saturated δ-lactones. In the case of 4,6-dimethyl-2H-pyran-2-one, the diastereoselectivity of the second hydrogenation step was determined by the chirality of the applied catalyst, while for the 4,5,6-trimethyl-2H-pyran2- one a double asymmetric induction effect was observed. Other cyclic substrates with endo- or exocyclic double bonds were hydrogenated, although with substantially lower enantioselectivity with respect to the 2-pyrones.
- Fehr, Matthias J.,Consiglio, Giambattista,Scalone, Michelangelo,Schmid, Rudolf
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p. 5768 - 5776
(2007/10/03)
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- Camphor-derived, chelating auxiliaries for the highly diastereoselective intermolecular Pauson-Khand reaction: Experimental and computational studies
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A family of enantiomerically pure (2R)-10-(alkylthio)isoborneols [methylthio (1), neopentylthio (2), phenylthio (3)], specifically designed as chiral auxiliaries suitable for chirality transfer to cobalt in Pauson-Khand reactions, has been synthesized. The dicobalt hexacarbonyl complexes of the alkoxyacetylenes derived from these alcohols (10a-12a) can be converted to the rather stable, internally chelated, pentacarbonyl complexes lOb-12b by treatment with NMO. The intermolecular Pauson-Khand reactions of 10b-12b with strained olefins take place with synthetically useful rates at low temperatures (down to -20 °C), with high yields and diastereoselectivities: norbornene (77%; 92:8), norbornadiene (82%; 96:4), bicyclo[3.2.0]hept-6-ene (91%; 93:7). The major diastereomer of the adduct of lOb with norbornadiene, 14, has been used as the starting point for a synthesis of (S)-(-)-4-alkyl-2-cyclopentenones through a se'quence consisting of completely diastereoselective conjugate addition, reductive cleavage with recovery (>95%) of the chiral auxiliary, and retro Diels-Alder reaction. The stereochemical course of the reaction of 10b with norbornadiene has been analyzed and rationalized by theoretical means by using a combined semiempirical [PM3-(tm)/density functional theory [VWN-Perdew-Wang 91] approach.
- Verdaguer, Xavier,Vazquez, Jordi,Fuster, Gerard,Bernardes-Genisson, Vania,Greene, Andrew E.,Moyano, Albert,Pericas, Miquel A.,Riera, Antoni
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p. 7037 - 7052
(2007/10/03)
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- Asymmetric catalytic intramolecular hydroacylation of 4-substituted pent-4-enals to β-substituted cyclopentanones
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The catalyst, [Rh(S,S-Me-duphos)(acetone)2]+, rapidly and efficiently converts 4-substituted pent-4-enals bearing primary and secondary substituents to the corresponding cyclopentanones and for a variety of substituents the ee was found to range from 93 to 96% at 25°C.
- Barnhart, Richard W.,McMorran, David A.,Bosnich
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p. 589 - 590
(2007/10/03)
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- Conjugate Additions of Organocuprates to Cycloalkenone Complexes of the Chiral Rhenium Lewis Acid 5-C5H5)Re(NO)(PPh3)>(+). Enantioselective Syntheses of 3-Substituted Cycloalkanones
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Reactions of organocuprates R2CuLi and cycloalkenone complexes (+)-(R)-(+)BF4(-) (n = 2, 1) are conducted in THF or CH2Cl2 between -15 deg C and -116 deg C.Workups with aqueous HI give the corresponding 3-substituted cycloalkanones and iodide complex (η5-C5H5)Re(NO)(PPh3) (I).Under optimized conditions, 3-substituted cyclohexanones are obtained in 39-83percent yields and 64-86percent ee (R = Me, R; n-Bu, R; t-Bu, S; Ph, S or R), and 3-substituted cyclopentanones are obtained in 50-73percent yields and 79-93percent ee (R = Me, R; Ph, S).Evidence for intermediate enolate complexes is presented, protocols for recycling the chiral rhenium auxiliary are described, and possible mechanisms of 1,4-asymmetric induction are discussed.
- Wang, Yan,Gladysz, J. A.
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p. 903 - 909
(2007/10/02)
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- Asymmetric catalysis. Asymmetric catalytic intramolecular hydroacylation of 4-pentenals using chiral rhodium diphosphine catalysts
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Catalysts of the type [Rh(chiral diphosphine)]+ convert 4-substituted 4-pentenals into the corresponding 3-substituted cyclopentanones with generally high turnover numbers and frequencies at 25 °C. The enantioselectivities of various substituted 4-pentenals with two chiral diphosphines have been explored. It was found that with the binap catalyst, almost complete enantioselectivity is observed for 4-pentenal substrates bearing 4-substituted tertiary substituents and for ester groups. Ketonic substituents give very high enantioselectivities. The mechanism of intramolecular hydroacylation has been explored, and it is suggested that an important consideration for obtaining high turnover frequencies is related to the acyl-alkyl reductive elimination mechanism which is inferred to occur by a process similar to ester hydrolysis. The origin of the enantioselection is discussed in terms of the interactions between the phenyl groups of the phosphine and the substituent of the pentenal.
- Barnhart, Richard W.,Wang, Xianqi,Noheda, Pedro,Bergens, Steven H.,Whelan, John,Bosnich
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p. 1821 - 1830
(2007/10/02)
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- Remote Control of Stereogenicity Transfer by Ring-Generated Anisotropic Orbital Overlap. Stereochemistry of Hydrogen Shift in the Intramolecular Reverse Ene Reaction of a cis-2- Alkyl-1 -alkenylcyclopropane
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The thermal rearrangement of cis-2-(2-propyl)-1(E)-propenylcyclopropane at temperatures near 230 °C in the gas phase occurs with activation parameters of Ea = 35.5 ±0.6 kcal/mol and log A = 12.05 ±0.5 (A, s-1). The optically active isotopically doubly labeled analogue (cis-2(S)-(2(S)-propyl-1-d3)-1(S)-(1(E)-propenyl-2-rf)cyclopropane 5 was synthesized in 12 steps from dicyciopentadiene. Pyrolysis of 5 gave only 2-methyl-octa-2(Z),5(Z)-diene-1-d3-7(S)-d, with high stereospecificity at each of the three sites of stereogenicity. This result is the one predicted if the reaction is controlled by optimal overlap ' of the reacting C-H and π bond orbitals with the Cs symmetric component of the degenerate 3E' highest occupied orbital of the cyclopropane ring.
- Parziale, Patti A.,Berson, Jerome A.
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p. 4595 - 4606
(2007/10/02)
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- CUPRATE ADDITIONS TO 5-METHOXYCYCLOPENTENONES: A NOVEL STEREOELECTRONIC EFFECT
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Cuprate additions to 5-methoxy-2-cyclopentenone have been found to proceed with moderate to extremely high diastereofacial selectivity, depending upon the specific cuprate and reaction protocol employed.Comparisons with related 5-substitued cyclopentenones suggest that the observed selectivity is not simply steric in nature, but instead reflects a novel stereoelectronic effect.
- Smith III, Amos B.,Dunlap, Norma K.,Sulikowski, Gary A.
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p. 439 - 442
(2007/10/02)
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- CATALYTIC ASYMMETRIC SYNTHESES II. HYDROGENATION OF α,β-UNSATURATED KETONES USING CHIRAL RUTHENIUM COMPLEXES
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α,β-Unsaturated ketones have been hydrogenated in the presence of HRuCl(TBPC)2 (TBPC) = (-)-trans-1,2-bis(diphenylphosphinomethyl)cyclobutane) to give ketones with a maximum optical purity of 62percent.Factors affecting the stereoselectivity of the catalytic reaction are discussed.
- Massonneau, Viviane,Maux, Paul Le,Simonneaux, Gerard
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p. 269 - 274
(2007/10/02)
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- ENZYMIC OPTICAL RESOLUTION AND FLASH VACUUM THERMOLYSIS IN CONCERT FOR THE SYNTHESIS OF OPTICALLY ACTIVE CYCLOPENTENONES
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A practical synthesis of enantiomerically pure cyclopentenones with a predeterminated absolute configuration has been realized, starting from optically active tricyclo2,6>decadienones.
- Klunder, A. J. H.,Huizinga, W. B.,Sessink, P. J. M.,Zwanenburg, B.
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p. 357 - 360
(2007/10/02)
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- 3. 2. 1.
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Preparative-scale horse liver alcohol dehydrogenase catalyzed oxidations of meso-1,3-bis(hydroxymethyl)cyclopentyl and -cyclohexyl substrates proceed stereospecifically to give 42-81% yields of the corresponding chiral bridged-bicyclic gamma -lactones of 100% ee. For each diol, oxidation of the hydroxymethyl group attached to the S center occurs exclusively. The stereospecificities observed are as predicted by the active-site model of the enzyme.
- Bridges,Raman,Ng,Jones
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p. 1461 - 1467
(2007/10/02)
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- ENANTIOCONTROLLED SYNTHESIS OF (S)-3-SUBSTITUTED CYCLOALKANONES FROM (S)-2-(p-TOLYLSULFINYL)-2-CYCLOALKENONES AND DIORGANOMAGNESIUM REAGENTS.
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By appropriate choice of reaction conditions, the same enantiomerically pure (S)-(+)-2-(p-tolylsulfinyl)cycloalkenone can be converted into either an (R)- or an (S)-3-substituted cycloalkanone in good to excellent enantiomeric purity.
- Posner, Gary H.,Hulce, Martin
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p. 379 - 382
(2007/10/02)
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