| 1. |
- Bartholomeyzik, Teresa, et al.
(author)
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Palladium-Catalyzed Oxidative Arylating Carbocyclization of Allenynes : Control of Selectivity and Role of H2O
- 2014
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In: Angewandte Chemie International Edition. - Weinheim : Wiley-VCH Verlag GmbH & Co. KGaA. - 1433-7851 .- 1521-3773. ; 53:33, s. 8696-8699
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Journal article (peer-reviewed)abstract
- Highly selective protocols for the carbocyclization/arylation of allenynes using arylboronic acids are reported. Arylated vinylallenes are obtained with the use of BF3 center dot Et2O as an additive, whereas addition of water leads to arylated trienes. These conditions provide the respective products with excellent selectivities (generally > 97:3) for a range of boronic acids and different allenynes. It has been revealed that water plays a crucial role for the product distribution.
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| 2. |
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| 3. |
- Diéguez, Montserrat, et al.
(author)
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Chiral pyranoside phosphite-oxazolines : a new class of ligand for asymmetric catalytic hydrogenation of alkenes
- 2008
-
In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 130:23, s. 7208-7209:130, s. 7208-7209
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Journal article (peer-reviewed)abstract
- We have described the first successful application of a phosphite-oxazoline ligand library in the asymmetric Ir-catalyzed hydrogenation of several unfunctionalized olefins. The introduction of a bulky biaryl phosphite moiety in the ligand design is highly adventitious in the product outcome. By carefully selecting the ligand components, we obtained high activities (TOFs up to >1500 mol x (mol x h)(-1) at 1 bar of H2) and enantioselectivities (ee values up to >99%) and, at the same time, show a broad scope for different substrate types. So, this is an exceptional ligand class that competes favorably with a few other ligand series that also provide high ee values for tri- and disubstituted substrate types.
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| 4. |
- Jiang, Tuo, et al.
(author)
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Palladium(II)/Bronsted Acid-Catalyzed Enantioselective Oxidative Carbocyclization-Borylation of Enallenes
- 2015
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In: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 54:20, s. 6024-6027
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Journal article (peer-reviewed)abstract
- An enantioselective oxidative carbocyclization-borylation of enallenes that is catalyzed by palladium(II) and a Bronsted acid was developed. Biphenol-type chiral phosphoric acids were superior co-catalysts for inducing the enantioselective cyclization. A number of chiral borylated carbocycles were synthesized in high enantiomeric excess.
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| 5. |
- Mazuela, Javier, et al.
(author)
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A new class of modular P,N-ligand library for asymmetric Pd-catalyzed allylic substitution reactions : a study of the key Pd-pi-allyl intermediates
- 2010
-
In: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 16:2, s. 620-638
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Journal article (peer-reviewed)abstract
- A new class of modular P,N-ligand library has been synthesized and screened in the Pd-catalyzed allylic substitution reactions of several substrate types. These series of ligands can be prepared efficiently from easily accessible hydroxyl-oxazole/thiazole derivatives. Their modular nature enables the bridge length, the substituents at the heterocyclic ring and in the alkyl backbone chain, the configuration of the ligand backbone, and the substituents/configurations in the biaryl phosphite moiety to be easily and systematically varied. By carefully selecting the ligand components, therefore, high regio- and enantioselectivities (ee values up to 96 %) and good activities are achieved in a broad range of mono-, di-, and trisubstituted linear hindered and unhindered substrates and cyclic substrates. The NMR spectroscopic and DFT studies on the Pd-pi-allyl intermediates provide a deeper understanding of the effect of ligand parameters on the origin of enantioselectivity.
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| 6. |
- Mazuela, Javier, et al.
(author)
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Adaptative Biaryl Phosphite-Oxazole and Phosphite-Thiazole Ligands for Asymmetric Ir-Catalyzed Hydrogenation of Alkenes
- 2010
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In: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 16:15, s. 4567-4576
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Journal article (peer-reviewed)abstract
- A library of readily available phosphite-oxazole/thiazole ligands (L1 a-g-L7 a-g) was applied in the Ir-catalyzed asymmetric hydrogenation of several largely unfunctionalized E- and Z-trisubstituted and 1,1-disubstituted terminal alkenes. The ability of the catalysts to transfer chiral information to the product could be tuned by choosing suitable ligand components (bridge length, the substituents in the heterocyclic ring and the alkyl backbone chain, the configuration of the ligand backbone, and the substituents/configurations in the biaryl phosphite moiety), so that enantioselectivities could be maximized for each substrate as required. Enantioselectivities were therefore excellent (enantiomeric excess (ee) values up to >99 %) for a wide range of E- and Z-trisubstituted and 1,1-disubstituted terminal alkenes. The biaryl phosphite moiety was a very advantageous ligand component in terms of substrate versatility.
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| 7. |
- 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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| 8. |
- Mazuela, Javier, et al.
(author)
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Palladium(II)-Catalyzed Tandem Oxidative Acetoxylation/ortho C-H Activation/Carbocyclization of Arylallenes
- 2015
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In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 137:30, s. 9559-9562
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Journal article (peer-reviewed)abstract
- Herein we report an example of tandem. oxidative acetoxylation/carbocyclization of arylallenes 1 using Pd(OAc)(2). The catalytic protocol is highly selective and provides access to new C-C and C-O bonds leading to a carbocyclization. The reaction proceeds via C-H activation by Pd. Mechanistic investigations show that the C-H activation is not the rate-limiting step and indicate that the reaction proceeds via acetoxylation of the allene.
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| 9. |
- Mazuela, Javier, et al.
(author)
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Phosphite-oxazole/imidazole ligands in asymmetric intermolecular Heck reaction
- 2011
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In: Organic and biomolecular chemistry. - : Royal Society of Chemistry (RSC). - 1477-0520 .- 1477-0539. ; 9:3, s. 941-946
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Journal article (peer-reviewed)abstract
- We describe the application of a new class of ligands -the phosphite-oxazole/imidazole (L1-L5a-g) in asymmetric intermolecular Pd-catalyzed Heck reactions under thermal and microwave conditions. These ligands combine the advantages of the oxazole/imidazole moiety with those of the phosphite moiety: they are more stable than their oxazoline counterparts, less sensitive to air and other oxidizing agents than phosphines and phosphinites, and easy to synthesize from readily available alcohols. The results indicate that activities, regio- and enantioselectivities, are highly influenced by the type of nitrogen donor group (oxazole or imidazole), the oxazole and biaryl-phosphite substituents and the axial chirality of the biaryl moiety of the ligand. By carefully selecting the ligand components, we achieved high activities, regio- (up to 99%) and enantioselectivities (up to 99%) using several triflate sources. Under microwave-irradiation conditions, reaction times were considerably shorter (from 24 h to 30 min) and regio- and enantioselectivities were still excellent.
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| 10. |
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