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- Coll, Mercedes, et al.
(author)
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Modular Furanoside Pseudodipeptides and Thioamides, Readily Available Ligand Libraries for Metal-Catalyzed Transfer Hydrogenation Reactions : Scope and Limitations
- 2012
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In: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 354:2-3, s. 415-427
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Journal article (peer-reviewed)abstract
- Two new highly modular carbohydrate-based, pseudodipeptide and thioamide ligand libraries have been synthesized for the rhodium- and ruthenium-catalyzed asymmetric transfer hydrogenation (ATH) of prochiral ketones. These series of ligands can be prepared efficiently from easily accessible D-xylose and D-glucose. The ligand libraries contain two main ligand structures (pseudodipeptide and thioamide) that have been designed by making systematic modifications to one of the most successful ligand families developed for the ATH. As well as studying the effect of these two ligand structures on the catalytic performance, we also evaluated the effect of modifying several of the ligand parameters. We found that the effectiveness of the ligands at transferring the chiral information in the product can be tuned by correctly choosing the ligand components (ligand structure and ligand parameters). Excellent enantioselectivities (ees up to 99%) were therefore obtained in both enantiomers of the alcohol products using a wide range of substrates.
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| 3. |
- Coll, Mercedes, et al.
(author)
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Second-Generation Amino Acid Furanoside Based Ligands from D-Glucose for the Asymmetric Transfer Hydrogenation of Ketones
- 2013
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In: ChemCatChem. - : Wiley. - 1867-3880 .- 1867-3899. ; 5:12, s. 3821-3828
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Journal article (peer-reviewed)abstract
- A novel series of modular amino acid thioamide ligands functionalized with carbohydrates were introduced and employed in the rhodium-catalyzed asymmetric transfer hydrogenation (ATH) of aryl alkyl ketones, including the less-studied heteroaromatic ketones. The ligands are based on amino acid hydroxyamides (pseudodipeptides), which are the most successful ligands previously used in asymmetric hydrogen transfer reactions. High enantioselectivities [up to 99% enantiomeric excess (ee)] were achieved in the ATH of a wide range of aryl alkyl ketones by using catalysts generated insitu from [RhCl2Cp*](2) (Cp*=C5Me5) and thioamide ligands comprising a 3-benzyl glucofuranoside backbone and a bulky isopropyl group in the -amino acid moiety. Interestingly, both enantiomers of the alcohol products can readily be obtained with high enantioselectivity by simply changing the absolute configuration of the -amino acid. The good performance can be extended to a very challenging class of industrially interesting heteroaromatic ketones (up to 99%ee).
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| 5. |
- Mazuela, Javier, et al.
(author)
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Iridium phosphite-oxazoline catalysts for the highly enantioselective hydrogenation of terminal alkenes
- 2009
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In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 131:34, s. 12344-12353
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Journal article (peer-reviewed)abstract
- A modular library of readily available phosphite-oxazoline ligands (L1-L16a-f) has been successfully applied for the first time in the Ir-catalyzed asymmetric hydrogenation of a broad range of highly unfunctionalized 1,1,-disubstituted terminal alkenes. Enantioselectivities up to >99% and full conversions were obtained in several 1,1-disubstituted alkenes, including substrate classes that have never been asymmetrically hydrogenated before (i.e., 1,1-heteoraryl-alkyl, 1,1-diaryl, trifluoromethyl, etc.). The results indicated that these catalytic systems have high tolerance to the steric and electronic requirements of the substrate and also to the presence of a neighboring polar group. The asymmetric hydrogenations were also performed using propylene carbonate as solvent, which allowed the Ir catalyst to be reused and maintained the excellent enantioselectivities.
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