Phosphine–phosphite ligands: chelate ring size vs. activity and enantioselectivity relationships in asymmetric hydrogenation

Farkas, Gergely; Balogh, Szabolcs; Madarász, József; Szöllősy, Áron; Darvas, Ferenç; Ürge, László; Gouygou, Maryse; Bakos, József

doi:10.1039/c2dt30386h

Cited by 19 publications

(7 citation statements)

References 48 publications

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“…[30] When no RA was used, the ee values ranged from 73 to 98 %( see Table 8). [31] Interestingly,l igands 3a and 4a gave very similarr esults, although slightly higher ee values and positive regulation effects associated with the use of an RA were obtained for ligand 3a,a sd etailed in the discussion that follows.…”

Section: Asymmetrich Ydrogenation Of Alkenes Catalyzed By Rh-complexementioning

confidence: 79%

“…[14] The binding of the bisphosphites 3a, 3b, 4a,o r4b to NaBArFo rC sBArFw as studied by using several spectroscopic techniques. Addition of increasing amounts of the RA to asolution of the bisphosphite (dichloromethane or toluene, plus am inimal amount of THF to ensure solubility of the RA throughout the titration) led to changes in the UV, 1 H, or 31 PNMR spectra. [15] Association constantsb etween the bisphosphitesa nd RAs were determined by multivariate factor analysis of titration data, considering a1 :1 bindingm odel (see Ta ble 1).…”

Section: Studies On Binding Of the Ligands 1-5a-d To The Rasmentioning

confidence: 99%

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Supramolecularly Regulated Ligands for Asymmetric Hydroformylations and Hydrogenations

Vidal‐Ferran

Mon

Bauzá

et al. 2015

Chemistry A European J

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Abstract:Herein we report the use of polyether binders as regulation agents (RAs) to enhance the enantioselectivity of rhodium-catalyzed transformations. For reactions of diverse substrates mediated by rhodium complexes of the ,-bisphosphite-polyether ligands 15,ad, the enantiomeric excess (ee) of hydroformylations was increased by up to 82% (substrate: vinyl benzoate, 96% ee), and the ee value of hydrogenations was increased by up to 5% (substrate: N-(1-(naphthalene-1-yl)vinyl)acetamide, 78% ee). The ligand design enabled the regulation of enantioselectivity by generation of an array of catalysts that simultaneously preserve the advantages of a privileged structure in asymmetric catalysis and offer geometrically close catalytic sites. The highest enantioselectivities in the hydroformylation of vinyl acetate with ligand 4b were achieved by using the Rb[B(3,5-(CF3)2C6H3)4 (RbBArF) as the RA. The enantioselective hydrogenation of the substrates 10 required the rhodium catalysts derived from bisphosphites 3a or 4a, either alone or in combination with different RAs (sodium, cesium or (R,R)-bis(1-phenylethyl)ammonium salts). This design approach was supported by results from computational studies.

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Section: Asymmetrich Ydrogenation Of Alkenes Catalyzed By Rh-complexementioning

confidence: 79%

Section: Studies On Binding Of the Ligands 1-5a-d To The Rasmentioning

confidence: 99%

Supramolecularly Regulated Ligands for Asymmetric Hydroformylations and Hydrogenations

Vidal‐Ferran

Mon

Bauzá

et al. 2015

Chemistry A European J

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“…14 In connection with this, Bakos and coworkers have shown an important influence of the length of the backbone in rhodium catalyzed olefin hydrogenation using BINOL and H 8 -BINOL based ligands with oxymethylene to oxybutylene bridges. 15 On the other hand, we have also observed that the use of bulkier, terc-butyl based phosphite fragments, has a profound effect on enantioselectivity in diverse olefin and imine hydrogenations. 10g, 12b Upon these considerations and as a complement to our previous work with ligands of types 1 and 2, we describe herein a study dealing with oxymethylene bridged ligands 3.…”

Section: Introductionmentioning

confidence: 85%

Asymmetric hydrogenation reactions with Rh and Ru complexes bearing phosphine–phosphites with an oxymethylene backbone

Kleman

Vaquero

Arribas

et al. 2014

Tetrahedron: Asymmetry

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Phosphine-phosphites 3a and 3b, derived from diphenylhydroxymethyl phosphine have been prepared. From these ligands [Rh(COD)(3a)]BF 4 (5a) and RuCl 2 (3b)[(S,S)-DPEN] (6b, DPEN = 1,2-diphenylethylenediamine) were synthesized and their structure determined by X-ray diffraction. Ligands 3 are characterized by a small bite angle of 83º. In addition, 5a led to an active catalyst for the hydrogenation of olefins, giving enantioselectivities up to 96 % ee. Likewise, compound 6b showed a good activity and enantioselectivity in the hydrogenation of N-1-phenyl ethylidene aniline and completed a reaction at S/C = 500 in 24 h with a 83 % ee.

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“…Enantiomeric excess values were confirmed by a Shimadzu HPLC LC8A with a 5u Lux Cellulose‐1 250 x 4.6 mm Phenomenex column (Substrate 11 , UV λ 250 nm, Hexane/Isopropanol 95/5, 25 °C; Substrate 9 and 12 , UV λ 215 nm, Hexane/Isopropanol 98/2, 25 °C). The absolute configurations of the materials were determined by comparison with reported data . Optical rotations were measured on a Jasco P‐1010 polarimeter at 25 °C.…”

Section: Methodsmentioning

confidence: 99%

Rh(I) complexes with new C₂‐symmetric chiral diphosphoramidite ligands: Catalytic activity for asymmetric hydrogenation of olefins

Drommi¹,

Arena²

2017

Applied Organom Chemis

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The design and synthesis of three new C 2 -symmetric chiral diphosphoramidite ligands starting from simple and cheap building blocks have been developed. Rhodium(I) cationic complexes bearing these chelate ligands have been prepared and applied in asymmetric hydrogenation of model olefins. A rhodium complex with a diphosphoramidite containing a chiral diamine configurationally stable and two fluxional chiral biphenyl units gave higher enantioselectivity with increasing hydrogen pressure (87% ee) in the hydrogenation of dimethyl itaconate. KEYWORDSasymmetric hydrogenation, C 2 -symmetric ligand, chiral rhodium complexes, diphosphoramidite | INTRODUCTIONThe development of a really worthwhile catalytic system for asymmetric synthesis is still a challenge for the chemical community. Presently, most efficient enantioselective catalysts are chiral ligand modified transition metal complexes. Therefore, the chiral environment generated by the enantiopure ligand coordinated to the metal is a crucial element in determining the outcome of the process.Although significant enantiomeric excesses were achieved with chiral metal complexes, the cost and availability of the ligands remain critical factors for larger scale applications. [1] Industrial demand for economical and modular chiral ligands have given rise to the development of rationally designed syntheses of chiral ligands derived from a simple and inexpensive enantiopure source. In this context, over the last years phosphoramidites have arisen as cheap and easily available chiral ligands for asymmetric catalysis. [2] Among catalytic asymmetric reactions, the hydrogenation of C¼C bond catalyzed by chiral ligand modified transition metal complexes is an important and efficient tool for the organic synthesis [3,4] and fine chemical production. [5] Several monodentate phosphoramidites as MonoPhos, SiPhos, DpenPhos, PipPhos, Morphos, PegPhos [6,7] as well as bidentate phosphine-phosphoramidites [8,9] have been applied in the rhodium catalyzed asymmetric hydrogenation of functionalized olefins with outstanding results. Although, diphosphoramidites are readily obtainable from inexpensive achiral/chiral diamines, only a few of them have been evaluated in the asymmetric hydrogenation. [10,2] Some years ago, we reported a family of C 2 -symmetric bidentate diphosphoramidite ligands containing the inexpensive chiral source (1R,2R)-diaminocyclohexane as the backbone and two biaryl units (Figure 1). We tested these P,P ligands in transition metal catalyzed asymmetric reactions such as conjugate addition, [11] hydrosilylation, [12] Diels-Alder [13] and hydrogenation. [14] Interestingly, we observed an uncommon positive H 2 pressure effect on the stereoselectivity in the Rh-catalyzed asymmetric hydrogenation of dimethyl itaconate using the diphosphoramidite (R,R,S a S a )-L2 which contains two (S)-BINOL (1,1′-binaphthalene-2,2′-diol) moieties.We also note that rhodium catalyst bearing the diphosphoramidite ligand L3 in which each BINOL-unit was replaced by a fluxional axially chir...

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Phosphine–phosphite ligands: chelate ring size vs. activity and enantioselectivity relationships in asymmetric hydrogenation

Cited by 19 publications

References 48 publications

Supramolecularly Regulated Ligands for Asymmetric Hydroformylations and Hydrogenations

Supramolecularly Regulated Ligands for Asymmetric Hydroformylations and Hydrogenations

Asymmetric hydrogenation reactions with Rh and Ru complexes bearing phosphine–phosphites with an oxymethylene backbone

Rh(I) complexes with new C₂‐symmetric chiral diphosphoramidite ligands: Catalytic activity for asymmetric hydrogenation of olefins

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Phosphine–phosphite ligands: chelate ring size vs. activity and enantioselectivity relationships in asymmetric hydrogenation

Cited by 19 publications

References 48 publications

Supramolecularly Regulated Ligands for Asymmetric Hydroformylations and Hydrogenations

Supramolecularly Regulated Ligands for Asymmetric Hydroformylations and Hydrogenations

Asymmetric hydrogenation reactions with Rh and Ru complexes bearing phosphine–phosphites with an oxymethylene backbone

Rh(I) complexes with new C2‐symmetric chiral diphosphoramidite ligands: Catalytic activity for asymmetric hydrogenation of olefins

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Rh(I) complexes with new C₂‐symmetric chiral diphosphoramidite ligands: Catalytic activity for asymmetric hydrogenation of olefins