Ligand Self‐Sorting and Nonlinear Effects in Dinuclear Asymmetric Hydrogenation: Complexity in Catalysis

Terrade, Frédéric G.; Lutz, Martin; Reek, Joost N. H.

doi:10.1002/chem.201301966

Cited by 15 publications

(20 citation statements)

References 59 publications

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“…The 31 P NMR spectrum of such a complex displays characteristic signals that consist of a doublet‐of‐doublets at δ ≈135 ppm (chelating ligand) and an AA′BB′XX′ pattern at δ ≈115 ppm (bridging ligand). The crystal structures of these dinuclear complexes exhibit very short distances between the BINOL moieties connected to geminal P atoms: the distance between the O atom from the BINOL moiety of the bridging ligand and the C atom from the BINOL moiety of the chelating ligand is less than 3.1 Å, which is significantly lower than the sum of the van der Waals radii (3.22 Å) and suggests the presence of lone pair–π interactions . This interaction is difficult to observe in solution, but it is expected to also give additional stabilization to the bimetallic structure if the complex is dissolved.…”

Section: Resultsmentioning

confidence: 92%

“…Before we applied mixtures of these ligands in catalysis, we first explored their coordination chemistry under various conditions. The coordination behavior of unfunctionalized BINOL‐METAMORPhos ligands ( Lan1 − and Lan2 − ) has been well established (Scheme a) . If Lan1 − (or Lan2 − ) is mixed with [Rh(nbd) 2 ]BF 4 (nbd=norbornadiene) under a hydrogen atmosphere, a dianionic dinuclear complex is formed selectively.…”

Section: Resultsmentioning

confidence: 99%

“…METAMORPhos ligands are effectively phosphorus ligands equipped covalently with weakly interacting sulfonamide anions (Scheme ). Recently, it was shown that dinuclear Rh complexes based on anionic ligands Lan2 − and Lan1 − are dianionic in the resting state, that is, four negative charges are located on ligands, two positive charges are located on the metal centers, and the overall charge is balanced by two positive charges of the triethylammonium counterions (Scheme a) . These complexes display a high efficiency for a number a substrates such as methyl‐2‐acetamidoacrylate, but also for the challenging cyclic enamides.…”

Section: Introductionmentioning

confidence: 99%

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Combinatorial Strategies to find New Catalysts for Asymmetric Hydrogenation Based on the Versatile Coordination Chemistry of METAMORPhos Ligands

Terrade

Kluwer²,

Detz³

et al. 2015

ChemCatChem

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To extend the toolbox and find improved catalysts, anionic METAMORPhos ligands and neutral amino‐acid‐based ligands were used separately and in mixtures to form Rh complexes used in the asymmetric hydrogenation of eight industrially relevant substrates. Spectroscopic studies showed that under the catalytic conditions, the mononuclear complex with two different ligands (the heterocombination) is the main complex in solution if both the anionic and neutral ligands have the same chirality. If the neutral ligand and the anionic ligand have the opposite chirality at the P atom, monometallic and bimetallic heterocomplexes were detected by NMR spectroscopy and MS. For the majority of substrates evaluated in this study, higher enantioselectivities were obtained if the complexes used were based on the heterocombination of an anionic and a neutral ligand compared to respective homocombinations. After we found the initial leads, higher turnover numbers and enantioselectivities could be obtained easily by further exploring focused ligand libraries. The superior activity of the complexes based on the different ligands is highlighted by their robustness: significant divergence from a 1:1 ratio between the ligands does not lower the selectivity of the catalyst, although more of the competing homocomplexes are formed under these conditions.

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Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Combinatorial Strategies to find New Catalysts for Asymmetric Hydrogenation Based on the Versatile Coordination Chemistry of METAMORPhos Ligands

Terrade

Kluwer²,

Detz³

et al. 2015

ChemCatChem

Self Cite

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show abstract

“…It has to be noted that complete stereocontrol corresponds only to a linear transmission of the chirality, in which the amplification factor converges to 1.0, as is seen in the right branch of the plot depicted in Figure 4 B. [28][29][30][31] The Table 1: Enantioselectivity of the bidirectional Rh I catalyst 3 in the asymmetric hydrogenation of (Z)methyl-a-acetamidocinnamate derivatives, dimethyl itaconate (6), and methyl-a-acetamidoacrylate (8). [27] Nonlinear effects in asymmetric hydrogenations were observed in catalysts built from (mixed) pairs of monophosphorus ligands, for example, phosphonites, phosphites, and phosphoramidites.…”

Section: Methodsmentioning

confidence: 99%

Temperature‐Controlled Bidirectional Enantioselectivity in a Dynamic Catalyst for Asymmetric Hydrogenation

Storch

Trapp

2015

Angew Chem Int Ed

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Asymmetric catalysis using enantiomerically pure catalysts is one of the most widely used methods for the preparation of enantiomerically pure compounds. The separate synthesis of both enantiomerically pure compounds requires tedious and time-consuming preparation of both enantiomerically pure catalysts or chiral separation of the racemic products. Here, we report a stereochemically flexible diastereomeric rhodium(I) catalyst for asymmetric hydrogenations of prochiral (Z)-α-acetamidocinnamates and α-substituted acrylates, which changes its enantioselectivity depending on the temperature to produce each enantiomerically pure compound in high yield with constant high enantioselectivity over time. The same axially chiral rhodium(I) catalyst produces (R)-phenylalanine derivatives in enantiomeric ratios of up to 87:13 (R/S) at low temperature and up to 3:97 (R/S) of the corresponding S enantiomers after re-equilibration of the same catalyst at elevated temperature.

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“…The implementation of sulfonamides was shown to be successful in the design of self‐sorting binuclear catalysts by Reek and colleagues. Independent of the ligands' enantiomeric ratio, only complexes with phosphoramidites of the same axial chirality were observed (Figure B) …”

Section: Introductionmentioning

confidence: 99%

A stereodynamic phosphoramidite ligand derived from 3,3′‐functionalized ortho‐biphenol and its rhodium(I) complex

et al. 2016

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Stereodynamic ligands and complexes bearing functional groups to attach chiral or achiral binding sites and auxiliaries are highly attractive due to the interesting opportunities for controlling the stereochemical outcome of enantioselective transformations. In this study we report the preparation of a 3,3'-functionalized biphenol (BIPOL) phosphoramidite ligand (P ) bearing 3,5-dichlorobenzoyl (3,5-DCB) amide binding sites for noncovalent interactions. Upon coordination to [Rh(COD) ]BF this substitution pattern directs one of the 3,5-DCB binding sites in close proximity of the metal center resulting in liberation of both COD ligands and the formation of a [Rh(P ) ]BF complex. Coordination of the amide carbonyl unit was found to be reversible, since the complex acted as an active catalyst in the hydrogenation of dehydroamino acid derivatives. X-ray crystallographic investigation revealed that the second 3,5-DCB unit is capable of forming noncovalent π-π interactions connecting both phosphoramidite ligands.

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Ligand Self‐Sorting and Nonlinear Effects in Dinuclear Asymmetric Hydrogenation: Complexity in Catalysis

Cited by 15 publications

References 59 publications

Combinatorial Strategies to find New Catalysts for Asymmetric Hydrogenation Based on the Versatile Coordination Chemistry of METAMORPhos Ligands

Combinatorial Strategies to find New Catalysts for Asymmetric Hydrogenation Based on the Versatile Coordination Chemistry of METAMORPhos Ligands

Temperature‐Controlled Bidirectional Enantioselectivity in a Dynamic Catalyst for Asymmetric Hydrogenation

A stereodynamic phosphoramidite ligand derived from 3,3′‐functionalized ortho‐biphenol and its rhodium(I) complex

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