- Indene Derived Phosphorus-Thioether Ligands for the Ir-Catalyzed Asymmetric Hydrogenation of Olefins with Diverse Substitution Patterns and Different Functional Groups
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A family of phosphite/phosphinite-thioether ligands have been tested in the Ir-catalyzed asymmetric hydrogenation of a range of olefins (50 substrates in total). The presented ligands are synthesized in three steps from cheap indene and they are air-stable solids. Their modular architecture has been crucial to maximize the catalytic performance for each type of substrate. Improving most Ir-catalysts reported so far, this ligand family presents a broader substrate scope, covering different substitution patterns with different functional groups, ranging from unfunctionalized olefins, through olefins with poorly coordinative groups, to olefins with coordinative functional groups. α,β-Unsaturated acyclic and cyclic esters, ketones and amides werehydrogenated in enantioselectivities ranging from 83 to 99% ee. Enantioselectivities ranging from 91 to 98% ee were also achieved for challenging substrates such as unfunctionalized 1,1′-disubstituted olefins, functionalized tri- and 1,1′-disubstituted vinyl phosphonates, and β-cyclic enamides. The catalytic performance of the Ir-ligand assemblies was maintained when the environmentally benign 1,2-propylene carbonate was used as solvent. (Figure presented.).
- Margalef, Jèssica,Biosca, Maria,de la Cruz-Sánchez, Pol,Caldentey, Xisco,Rodríguez-Escrich, Carles,Pàmies, Oscar,Pericàs, Miquel A.,Diéguez, Montserrat
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supporting information
p. 4561 - 4574
(2021/04/05)
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- Fluoride Anions in Self-Assembled Chiral Cage for the Enantioselective Protonation of Silyl Enol Ethers
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The potential of Song's chiral oligoethylene glycols (oligoEGs) as catalysts was explored in the enantioselective protonation of trimethylsilyl enol ethers in combination with alkali metal fluoride (KF and CsF) and in the presence of a proton source. Highly enantioselective protonations of various silyl enol ethers of α-substituted tetralones were achieved, producing chiral α-substituted tetralones in full conversion and with up to 99% ee. The established protocol was successfully extended to the synthesis of biologically relevant chiral α-substituted chromanone and thiochromanone derivatives.
- Paladhi, Sushovan,Liu, Yidong,Kumar, B. Senthil,Jung, Min-Jung,Park, Sang Yeon,Yan, Hailong,Song, Choong Eui
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supporting information
p. 3279 - 3282
(2017/06/23)
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- Rhodium-Catalyzed Enantioselective Isomerization of Secondary Allylic Alcohols
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The first catalytic enantioselective isomerization of secondary allylic alcohols to access ketones with a α-tertiary stereocenter is presented. The racemic allylic alcohol substrates can be converted to the enantioenriched ketone products in a stereoconvergent fashion. The use of commercially available catalysts and mild reaction conditions makes this an attractive method in stereoselective synthesis.
- Liu, Tang-Lin,Ng, Teng Wei,Zhao, Yu
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supporting information
p. 3643 - 3646
(2017/03/20)
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- Investigation of a novel diamine based chiral auxiliary in the asymmetric alkylation of ketones
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A novel chiral auxiliary containing a pyrrolidine ring has been utilised in the preparation of various chiral ketones with good to excellent enantioselectivities (up to 92%). It has been successfully employed in aldol and Michael reactions giving moderate to high selectivity.
- Clarke, Sarah L.,McSweeney, Christina M.,McGlacken, Gerard P.
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p. 356 - 361
(2014/04/03)
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- Expanded scope of the asymmetric hydrogenation of minimally functionalized olefins catalyzed by iridium complexes with phosphite-thiazoline ligands
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We have replaced the oxazoline group with a thiazoline moiety in one of the most successful of the phosphite-oxazoline ligand families for the Ir-catalyzed hydrogenation of minimally functionalized olefins. A small but structurally important library of Ir phosphite-thiazoline precatalysts (Ir-L1-L2a-e) has been developed by changing the substituents/configurations at the biaryl phosphite group. We found that the replacement of the oxazoline with a thiazoline moiety in the ligand design is beneficial in terms of substrate scope.
- Mazuela, Javier,Pamies, Oscar,Dieguez, Montserrat
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p. 2410 - 2417
(2013/08/23)
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- Pyranoside phosphite-oxazoline ligands for the highly versatile and enantioselective Ir-catalyzed hydrogenation of minimally functionalized olefins. A combined theoretical and experimental study
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A modular set of phosphite-oxazoline (P,N) ligands has been applied to the title reaction. Excellent ligands have been identified for a range of substrates, including previously challenging terminally disubstituted olefins, where we now have reached enantioselectivities of 99% for a range of substrates. The selectivity is best for minimally functionalized substrates with at least a moderate size difference between geminal groups. A DFT study has allowed identification of the preferred pathway. Computational prediction of enantioselectivities gave very good accuracy.
- Mazuela, Javier,Norrby, Per-Ola,Andersson, Pher G.,Pamies, Oscar,Dieguez, Montserrat
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supporting information; experimental part
p. 13634 - 13645
(2011/10/10)
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- Highly enantioselective construction of the α-chiral center of amides via iridium-catalyzed hydrogenation of α,β-unsaturated amides
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The chiral center at the a-position of amides is installed in excellent enantioselectivity via the iridium-catalyzed asymmetric hydrogenation of αβ-unsaturated amides under mild conditions. Even aliphatic amides are suitable substrates. The presence of a
- Lu, Wei-Jing,Hou, Xue-Long
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supporting information; scheme or table
p. 1224 - 1228
(2009/12/06)
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- Highly enantioselective synthesis of optically active ketones by iridium-catalyzed asymmetric hydrogenation
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(Chemical Equation Presented) Close to perfect enantioselectivity (up to 99% ee, see scheme) is found for the formation of α-substituted ketones by the asymmetric hydrogenation of enones with an iridium-phosphinooxazoline catalyst. In an operationally simple process, both linear and cyclic substrates react well and afford the desired products in high yields. A wide variety of substituents are tolerated, thus making the method synthetically appealing.
- Lu, Sheng-Mei,Bolm, Carsten
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supporting information; experimental part
p. 8920 - 8923
(2009/05/30)
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- Application of A Recyclable Pseudoephedrine Resin in Asymmetric Alkylations on Solid Phase
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A pseudoephedrine resin has been successfully employed in asymmetric alkylations on solid phase. Immobilized pseudoephedrine amides are conveniently prepared by the one-step attachment of pseudoephedrine to Merrifield resin through the hydroxyl group and subsequent acylation on nitrogen. Deprotonation and alkylation of the resin-bound amides proceeds smoothly. Ketones and alcohols are cleaved from the resin in high enantiomeric excess and moderate to good overall yield. The parallel, asymmetric solid-phase synthesis of a small library of chiral ketones and alcohols has been carried out to illustrate the utility of the approach. Finally, the pseudoephedrine resin can be conveniently recycled and utilized with no significant loss in the yield or enantiomeric excess of the products.
- Hutchison, Panee C.,Heightman, Tom D.,Procter, David J.
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p. 790 - 801
(2007/10/03)
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- Evaluation of a Pseudoephedrine Linker for Asymmetric Alkylations on Solid Phase
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(Equation Presented) Immobilized pseudoephedrine amides have been conveniently prepared by attachment of pseudoephedrine to Merrifield resin and acylation on nitrogen. Deprotonation and alkylation of the resin bound amides proceeds smoothly. Products were cleaved from the resin to give ketones and alcohols in high enantiomeric excess and moderate to good overall yield.
- Hutchison, Panee C.,Heightman, Tom D.,Procter, David J.
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p. 4583 - 4585
(2007/10/03)
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- Non-destructive Removal of the Bornanesultam Auxiliary in α-Substituted N-Acylbornane-10,2-sultams under Mild Conditions: An Efficient Synthesis of Enantiomerically Pure Ketones and Aldehydes
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α-Substituted N-acylbornane-10,2-sultams 6, 9, and 10 can be converted into enantiomerically pure ketones 5, 13, and 14, respectively, via a two-step procedure involving a known mercaptolysis reaction followed by an -mediated coupling of the resulting S-benzyl thioesters with Grignard reagents.Furthermore, enantiomerically pure aldehydes 23 can be obtained from α-substituted N-acylbornane-10,2-sultams 6 via a one-step reduction with (i-Bu)2AlH.No epimerization at the α-chiral center is observed during the cleavage reaction whereby the chiral auxiliary, bornane-10,2-sultam 1 or ent-1, was recovered.By using this methodology, several natural products or precursors thereof can be prepared.
- Oppolzer, Wolfgang,Darcel, Christophe,Rochet, Patrick,Rosset, Stephane,Brabander, Jef De
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p. 1319 - 1337
(2007/10/03)
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- Syntheses of optically active γ-ketothiols and the esters by lipase-catalyzed hydrolysis via α-acetylthiomethylation of ketones
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The α-acetylthiomethylation of ketones was achieved by the reaction of ketones or the enamines with N,N-bis-(acetylthiomethyl)-p-chloroaniline in the presence of trifluoroacetic acid. The resulting thiolesters were hydrolyzed enantioselectively by catalys
- Izawa, Tomohiko,Terao, Yoshiyasu,Suzuki, Kunio
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p. 2645 - 2648
(2007/10/03)
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