Adaptable P–X Biaryl Phosphite/Phosphoroamidite‐Containing Ligands for Asymmetric Hydrogenation and C–X Bond‐Forming Reactions: Ligand Libraries with Exceptionally Wide Substrate Scope

Pàmies, Òscar; Diéguez, Montserrat

doi:10.1002/tcr.201600062

Cited by 21 publications

(15 citation statements)

References 161 publications

(76 reference statements)

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“…Moreover, as Diéguez and coworkers have shown, the flexibility of tropos ligands has proven beneficial for a variety of Pd-catalyzed allylic substitutions because the flexible backbone can accommodate both hindered and unhindered substrates. 18,19 They have shown that phosphite, phosphonite, and phosphite-thioether tropos ligands are quite effective. 18, 19c For example, phosphite-oxazoline tropos ligands such as 2 were developed for the allylic substitution of three sterically different substrate classes including 3–5 (Scheme 3a).…”

Section: Tropos Ligandsmentioning

confidence: 99%

“…18,19 They have shown that phosphite, phosphonite, and phosphite-thioether tropos ligands are quite effective. 18, 19c For example, phosphite-oxazoline tropos ligands such as 2 were developed for the allylic substitution of three sterically different substrate classes including 3–5 (Scheme 3a). 20 Beyond the fact that the use of phosphite ligands increases reaction rates over phosphines, the flexible biphenyl backbone of the ligand increases catalyst adaptability.…”

Section: Tropos Ligandsmentioning

confidence: 99%

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Conformational Dynamics in Asymmetric Catalysis: Is Catalyst Flexibility a Design Element?

Crawford

Sigman

2019

Synthesis

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Traditionally, highly selective low molecular weight catalysts have been designed to contain rigidifying structural elements. As a result, many proposed stereochemical models rely on steric repulsion for explaining the observed selectivity. Recently, as is the case for enzymatic systems, it has become apparent that some flexibility can be beneficial for imparting selectivity. Dynamic catalysts can reorganize to maximize attractive non-covalent interactions that stabilize the favored diastereomeric transition state, while minimizing repulsive non-covalent interactions for enhanced selectivity. This short review discusses catalyst conformational dynamics and how these effects have proven beneficial for a variety of catalyst classes, including tropos ligands, cinchona alkaloids, hydrogen-bond donating catalysts, and peptides.1 Introduction2 Tropos Ligands3 Cinchona Alkaloids4 Hydrogen-Bond Donating Catalysts5 Peptide Catalysts6 Conclusion

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Section: Tropos Ligandsmentioning

confidence: 99%

Section: Tropos Ligandsmentioning

confidence: 99%

Conformational Dynamics in Asymmetric Catalysis: Is Catalyst Flexibility a Design Element?

Crawford

Sigman

2019

Synthesis

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“…We and others have shown the benefits of having biaryl phosphite moieties in the ligands for several asymmetric catalytic transformations ,–. Our group has contributed with an improved generation of phosphite‐N ligand libraries . In this context, we found that replacing the phosphine moiety in phosphine‐oxazoline PHOX ligands by a biaryl phosphite moiety not only improved activity but also increased substantially the substrate scope in the Pd‐allylic substitution and the Ir‐catalyzed hydroboration .…”

Section: Introductionmentioning

confidence: 82%

“…Our group has expertise in preparing easy to handle ligand families from readily available starting materials . We and others have shown the benefits of having biaryl phosphite moieties in the ligands for several asymmetric catalytic transformations ,–. Our group has contributed with an improved generation of phosphite‐N ligand libraries .…”

Section: Introductionmentioning

confidence: 99%

“…The reason for this exceptional performance is the flexiblility of the biaryl phosphite group that allows the chiral pocket of the catalyst to accommodate itself according to the steric demands of the substrate . Moreover, their easy preparation from alcohols and their higher stability towards air and other oxidizing agents than other commonly used phosphines make phosphite ligands very attractive ,–. These features facilitate preparing large series of ligands in the quest to maximize catalytic performance for each particular reaction and substrate.…”

Section: Introductionmentioning

confidence: 99%

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Alternatives to Phosphinooxazoline (t‐BuPHOX) Ligands in the Metal‐Catalyzed Hydrogenation of Minimally Functionalized Olefins and Cyclic β‐Enamides

et al. 2017

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This studyp resents an ew serieso fr eadily accessible iridium-and rhodium-phosphite/oxazoline catalytic systems that can efficiently hydrogenate,f or the first time,b othm inimally functionalized olefins and functionalized olefins (62 examples in total) in high enantioselectivities( eesu pt o> 99%) and conversions. Thep hosphite-oxazoline ligands,w hich are readily available in only two synthetic steps,a re derived from previous privileged 4-alkyl-2-[2-(diphenylphosphino)phenyl]-2-oxazoline (PHOX) ligands by replacing the phosphinemoiety by ab iaryl phosphite group and/or the introductiono famethylene spacer between the oxazoline and the phenylr ing. The modular design of the ligands hasgiven us the opportunity not only to overcome the limitations of the iridium-PHOX catalytic systems in the hydrogenation of minimally functionalized Z-olefins and 1,1-disubstitutedo lefins, but also to expand theiru se to unfunctionalized olefins containing other challenging scaffolds (e.g.,e xocyclic benzofused andt riaryl-substitutedo lefins) anda lso to olefinsw ith poorly coor-dinativeg roups (e.g., a,b-unsaturated lactams,l actones,a lkenylboronic esters, etc.) with enantioselectivities typically > 95% ee. Moreover, both enantiomers of the hydrogenation product could be obtained by simply changing the configuration of the biaryl phosphite moiety.R emarkably, the new catalytic systems also provided excellent enantioselectivities (up to 99% ee)i nt he asymmetric hydrogenation of another challengingc lass of olefins -t he functionalized cyclic b-enamides.A gain, both enantiomers of the reduceda midesc ould be obtained by changing the metal from Ir to Rh. We also demonstrated that environmentally friendly propylene carbonate can be used with no loss of enantioselectivity.A nothera dvantage of the new ligands over the PHOX ligands is that the best ligands are derived from the affordable (S)-phenylglycinolr ather than from the expensive (S)-tert-leucinol.

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Synthesis, Application and Kinetic Studies of Chiral Phosphite‐Oxazoline Palladium Complexes as Active and Selective Catalysts in Intermolecular Heck Reactions

et al. 2018

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This study identifies new phosphite-oxazoline ligands that have been successfully applied in the palladiumcatalyzed intermolecular asymmetric Heck reaction. The design of the new phosphite-oxazoline ligands derives from a previous successful generation of phosphine-oxazoline ligands, by replacing the phosphine group with several πacceptor biaryl phosphite moieties. With these simple modifications, the new phosphite-based ligands, unlike previous phosphine-oxazoline, not only present a modular design with numerous potential phosphite groups available, but they are also air-stable solids, which can be made in the same number of synthetic steps as the phosphine analogues. The substitution of the phosphine by a biaryl phosphite group extended the range of substrates and triflates sources that can be coupled with regio-, enantioselectivities and activities comparable to the few best ones reported. In addition, the ligands that provided the best selectivities contained an isopropyl oxazoline moiety instead of the tert-butyl group found in the related phosphine-oxazoline ligands, which is made from a much more expensive precursor. In this paper we have also carried out kinetic studies and a Hammett plot analysis to determine the rate determining step of this system in the regime of interest. We suggest a likely explanation for the fast Heck reaction of the phosphite-oxazoline catalysts.

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Adaptable P–X Biaryl Phosphite/Phosphoroamidite‐Containing Ligands for Asymmetric Hydrogenation and C–X Bond‐Forming Reactions: Ligand Libraries with Exceptionally Wide Substrate Scope

Abstract: In this personal review, we present our efforts in the design of ligand libraries for the discovery of suitable metal catalysts for asymmetric hydrogenation and C-X bond-forming reactions.

Cited by 21 publications

References 161 publications

Conformational Dynamics in Asymmetric Catalysis: Is Catalyst Flexibility a Design Element?

Conformational Dynamics in Asymmetric Catalysis: Is Catalyst Flexibility a Design Element?

Alternatives to Phosphinooxazoline (t‐BuPHOX) Ligands in the Metal‐Catalyzed Hydrogenation of Minimally Functionalized Olefins and Cyclic β‐Enamides

Synthesis, Application and Kinetic Studies of Chiral Phosphite‐Oxazoline Palladium Complexes as Active and Selective Catalysts in Intermolecular Heck Reactions

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