PHOX Ligands

Bausch, Cory C.; Pfaltz, Andreas

doi:10.1002/9783527635207.ch6

Cited by 23 publications

(12 citation statements)

References 103 publications

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“…The enantioselective synthesis of molecules bearing allylic stereogenic centers is an important undertaking due to the prevalence of this motif in a large number of natural products and bioactive compounds and the influence of the stereogenic center in subsequent diastereoselective transformations of the olefin . The union of two reactants through allylic substitution is a hallmark method for generating this scaffold but does not often afford compounds with 1,2-disubstituted alkenes. − Enantioselective reactions of acyclic 1,3-dienes provide one route to chiral allyl fragments that bear 1,2-disubstituted olefins, and hydrofunctionalizations are a significant subset of these.…”

Section: Introductionmentioning

confidence: 99%

Development and Mechanistic Investigations of Enantioselective Pd-Catalyzed Intermolecular Hydroaminations of Internal Dienes

Park

Malcolmson

2018

ACS Catal.

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We report the development of highly enantio- and regioselective Pd-catalyzed intermolecular hydroaminations of challenging 1,4-disubstituted acyclic dienes. Several aryl/alkyl-disubstituted dienes and a sterically differentiated alkyl/alkyl-disubstituted diene undergo coupling with a variety of secondary aliphatic amines, indoline, and primary anilines to generate allylic amines with myriad α-alkyl groups in up to 78% yield, >98:2 rr, and 98.5:1.5 er. A number of experiments, including deuterium labeling and transamination studies, shed light on mechanistic details of the reaction, such as the reversibility of individual steps of the proposed catalytic cycle and of the reaction as a whole.

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Section: Introductionmentioning

confidence: 99%

Development and Mechanistic Investigations of Enantioselective Pd-Catalyzed Intermolecular Hydroaminations of Internal Dienes

Park

Malcolmson

2018

ACS Catal.

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“…We then turned our attention to phosphinooxazoline (PHOX) ligands, which have enjoyed a great deal of success in enantioselective allylic substitution, but to the best of our knowledge have not been employed in hydrofunctionalization reactions . We began by examining the Ph-substituted PHOX ligand L1 (Table , entry 1).…”

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confidence: 99%

Enantioselective Intermolecular Addition of Aliphatic Amines to Acyclic Dienes with a Pd–PHOX Catalyst

2017

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We report a method for the catalytic, enantioselective intermolecular addition of aliphatic amines to acyclic 1,3-dienes. In most cases, reactions proceed efficiently at or below room temperature in the presence of 5 mol % of a Pd catalyst bearing a PHOX ligand, generating allylic amines in up to 97:3 er. The presence of an electron-deficient phosphine within the ligand not only leads to a more active catalyst but also is critical for achieving high site selectivity in the transformation.

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“…PHOX ligands are nonsymmetrical ligands which can coordinate to a metal center through their N- and P-moieties. They are usually prepared from amino acids or from the corresponding amino alcohols [ 9 , 13 ]. Some examples of literature-known PHOX ligands are shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

“…1 ( 1a – d ). These ligands gave up to 96% ee by their application in allylic substitution with dimethyl malonate as nucleophile [ 13 – 14 ]. The design of new PHOX ligands is still subject to current research and the synthesis of a lot of different PHOX ligands have been reported during the last years [ 15 – 18 ].…”

Section: Introductionmentioning

confidence: 99%

D-Fructose-based spiro-fused PHOX ligands: synthesis and application in enantioselective allylic alkylation

Imrich

Kraft

Maichle‐Mößmer

et al. 2018

Beilstein J. Org. Chem.

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Phosphinooxazoline (PHOX) ligands are an important class of ligands in asymmetric catalysis. We synthesized ten novel D-fructose-derived spiro-fused PHOX ligands with different steric and electronic demand. The application of two of them was tested in asymmetric allylic alkylation. The ligands are prepared in two steps from readily available 1,2-O-isopropylidene protected β-D-fructopyranoses by the BF3·OEt2-promoted Ritter reaction with 2-bromobenzonitrile to construct the oxazoline moiety followed by Ullmann coupling of the resulting aryl bromides with diphenylphosphine. Both steps proceeded mostly in good to high yields (57–86% for the Ritter reaction and 35–89% for the Ullmann coupling). The Ritter reaction gave two anomers, which could be separated by column chromatography. The prepared ligands showed promising results (er of up to 84:16) in Tsuji–Trost reactions with diphenylallyl acetate as model substrate.

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PHOX Ligands

Cited by 23 publications

References 103 publications

Development and Mechanistic Investigations of Enantioselective Pd-Catalyzed Intermolecular Hydroaminations of Internal Dienes

Development and Mechanistic Investigations of Enantioselective Pd-Catalyzed Intermolecular Hydroaminations of Internal Dienes

Enantioselective Intermolecular Addition of Aliphatic Amines to Acyclic Dienes with a Pd–PHOX Catalyst

D-Fructose-based spiro-fused PHOX ligands: synthesis and application in enantioselective allylic alkylation

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