[CpRu((R)-Binop-F)(H2O)][SbF6], a New Fluxional Chiral Lewis Acid Catalyst:  Synthesis, Dynamic NMR, Asymmetric Catalysis, and Theoretical Studies

Alezra, Valérie; Bérnardinelli, Gerald; Corminbœuf, Clémence; Frey, Urban; Kündig, E. Peter; Merbach, André E.; Saudan, C; Viton, Florian; Weber, Jacques

doi:10.1021/ja0374123

Cited by 75 publications

(51 citation statements)

References 81 publications

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“…[3] The introduction of electron-withdrawing groups R at the coordinating phosphorus atom will increase the Lewis acidity of the transition-metal atom, [4] which again influences the catalytic activity of the corresponding transition-metal complex. [5] In particular, the implementation of the strongly electron-withdrawing CF 3 group causes high p acidity of the phosphane ligand. [6] The bis(trifluoromethyl)phosphinous acid (CF 3 ) 2 POH, synthesized in 1960 by Griffiths and Burg, [7,8,9] represents to date the only known example of a diorganylphosphinous acid.…”

Section: Introductionmentioning

confidence: 99%

The Bis(pentafluoroethyl)phosphinous Acid (C₂F₅)₂POH

Hoge¹,

Bader²,

Beckers³

et al. 2009

Chemistry A European J

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The industrial product (C(2)F(5))(3)PF(2) is transformed into the phosphinic acid chloride (C(2)F(5))(2)P(O)Cl, which reacts with an excess of Bu(3)SnH in a clean, multistep reaction to give the stannyl derivative (C(2)F(5))(2)POSnBu(3). Subsequent treatment with gaseous HBr leads to the formation of (C(2)F(5))(2)POH, which is isolated in 70 % yield. Besides (CF(3))(2)POH, bis(pentafluoroethyl)phosphinous acid, (C(2)F(5))(2)POH, represents the second known example of a phosphinous acid that is predicted by using density functional theory calculations at the B3PW91/6-311G(3d,p) level to be more stable than the phosphane oxide tautomer, the energy difference being 11.7 kJ mol(-1). Only the phosphinous acid isomer is detectable in the gas phase and in solution. However, investigations of the neat liquid reveal a temperature-dependent tautomeric equilibrium with the phosphane oxide isomer (C(2)F(5))(2)P(O)H, which is characterized by vibrational and multinuclear NMR spectroscopic methods in combination with quantum-chemical calculations.

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Section: Introductionmentioning

confidence: 99%

The Bis(pentafluoroethyl)phosphinous Acid (C₂F₅)₂POH

Hoge¹,

Bader²,

Beckers³

et al. 2009

Chemistry A European J

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“…[1] For example, Kündig and co-workers successfully used chiral bidentate bis(pentafluorophenyl)phosphinite ligands to create weak iron-and ruthenium-containing Lewis acids to activate enals and effectively catalyze their asymmetric Diels-Alder reactions with dienes and 1,3-dipolar cycloaddition reactions with nitrones. [2] In addition, electron-poor phosphane ligands (partly fluorinated BINAP derivatives) were shown, in some cases, to be more efficient in asymmetric hydrogenations than their nonfluorinated counterparts. [3] The influence of electron-poor phosphane ligands is described by using the nonsymmetric diphosphane complexes [M(Cl) 2 Ph 2 PCH 2 CH 2 PA C H T U N G T R E N N U N G (CF 3 ) 2 ] with M = Pd, Pt as examples.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of the First Chiral Bidendate Bis(trifluoromethyl)phosphane Ligand through Stabilization of the Bis(trifluoromethyl)phosphanide Anion in the Presence of Acetone

Hoge

Thösen

Pantenburg

2006

Chemistry A European J

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Lewis acid/Lewis base adduct formation of the P(CF3)2- ion and acetone leads to a reduced negative hyperconjugation and, therefore, limits the C--F bond activation. The resulting increased thermal stability of the P(CF3)2- ion in the presence of acetone allows selective substitutions and enables the synthesis of the first example of a chiral, bidentate bis(trifluoromethyl)phosphane ligand: a DIOP derivative, [(2,2-dimethyl-1,3-dioxolane-4,5-diyl)bis(methylene)]bis(diphenylphosphane), in which the phenyl groups at the phosphorus atoms are replaced by strong electron-withdrawing trifluoromethyl groups. The resulting high electron-acceptor strength of the synthesized bidentate (CF3)2P ligand is demonstrated by a structural and vibrational study of the corresponding tetracarbonyl-molybdenum complex. The stabilization of the P(CF3)2- ion in the presence of acetone is based on the formation of a dynamic Lewis acid/Lewis base couple, (CF3)2PC(CH3)2O-. Although there is no spectroscopic evidence for the formation of the formulated alcoholate ion, the intermediate formation of (CF3)2PC(CH3)2O- could be proved through the reaction with (CF3)2PP(CF3)2, which yields the novel phosphane-phosphinite ligand (CF3)2PC(CH3)2OP(CF3)2. This ligand readily forms square-planar Pt(II) complexes upon treatment with solid PtCl2.

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“…[9] However, we anticipated that there are other oxidizable substrates in whose presence Rh 2 5+ will be reduced to Rh 2 4+ ; thus, one procedural requirement of our investigation has been to test the redox stability of the reacting partners with the Rh 2 5+ catalyst. One of the significant challenges in asymmetric Lewis acid catalysis is a 1,3-dipolar cycloaddition between nitrones and enals [10][11][12][13] to form isoxazolidines. A variety of chiral catalysts have been used for the transformation with methacrolein, which occurs in variable yields, usually below room temperature, with the use of 5-10 mol % of catalyst and excess methacrolein ( Table 2).…”

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confidence: 99%

“…A variety of chiral catalysts have been used for the transformation with methacrolein, which occurs in variable yields, usually below room temperature, with the use of 5-10 mol % of catalyst and excess methacrolein ( Table 2). Ruthenium and iron catalysts ( Table 2, entries 1-2) appear to favor the formation of 2, [10,11] and the only example of a nickel catalyst (Table 2, entry 5, with chiral ligand 3, which is shown in Scheme 2) shows complete selectivity for the formation of 2.…”

mentioning

confidence: 99%

Cationic Chiral Dirhodium Carboxamidates Are Activated for Lewis Acid Catalysis

Wang¹,

Wolf²,

Zavalij³

et al. 2008

Angew Chem Int Ed

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Dedicated to Professor Henri Brunner on the occasion of his 72nd birthday Chiral dirhodium(II) carboxamidates have high potential for enantioselective Lewis acid catalyzed reactions because they hold the Lewis base, which is activated for reaction, at the axial coordination site in close proximity to the ligand attachments for chiral differentiation. As has already been demonstrated for the hetero-Diels-Alder reaction (Scheme 1) [1,2] and for trimethylsilylketene/glyoxal cycloaddition, [3] the chiral environment around the axial coordination site strongly influences enantiocontrol and also pushes the product off the rhodium axial coordination site to provide turnover numbers (TON) as high as 10 000. However, the Lewis acidity for dirhodium(II) carboxamidates is low compared to that of many other catalysts for these reactions.[4] Suitable Diels-Alder, ene, and dipolar cycloaddition reactions, for example, show no catalytic activity with chiral dirhodium(II) carboxamidates, even with a,adifluoro analogues of the mepy and meaz catalysts that were developed to enhance Lewis acid association with Lewis bases.[5] We have prepared cationic Rh II /Rh III counterparts to the moderately active chiral dirhodium(II) carboxamidates to enhance the Lewis acidity of these chiral dirhodium catalysts. Cationic metal complexes are now commonly used to achieve rate and selectivity enhancements for those transformations suitable to catalysis by the cationic metal complex.[6] We anticipated that cationic chiral Rh II /Rh III compounds could increase the closeness of association of the catalyst with Lewis bases, increase the rate of reaction with selected substrates, and enhance enantiocontrol.Oxidation of dirhodium(II) (Rh 2 4+ ) compounds is well known ,[6] but their Rh 2 5+ counterparts have been produced in the presence of either a less labile ligand such as halide [7] or by using another transition metal such as Ag I , Ce IV , or Cu II for the oxidation, [6,8] none of which are amenable to the use of Rh 2 5+ complexes as catalysts without laborious separation or further catalyst manipulation. However, we have recently discovered that nitrosonium salts effect facile oxidation of dirhodium(II) carboxamidates at room temperature to form the corresponding Rh II /Rh III salts quantitatively, evolving nitric oxide in the process. These complexes exhibit a characteristic electronic absorption near 1000 cm À1 . A crystal structure for the bis(acetonitrile) complex of [Rh 2 {(4S)-meox} 4 ]BF 4 is shown in Figure 1.To test the ability of chiral Rh 2 5+ carboxamidates to enhance selectivity in Lewis acid catalyzed transformations we turned our attention to the hetero-Diels-Alder reaction and to [Rh 2 (mepy) 4 ] as the catalyst. As has been reported, [1a] the use of 1.0 mol % [Rh 2 (mepy) 4 ] with p-nitrobenzaldehyde and the Danishefsky diene (see Scheme 1) resulted in the corresponding hetero-Diels-Alder product (53 % yield) in 73 % ee; use of the corresponding Rh 2 5+ complex, [Rh 2 {(5S)-mepy} 4 ]BF 4 , produced the same product in 93 %...

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[CpRu((R)-Binop-F)(H₂O)][SbF₆], a New Fluxional Chiral Lewis Acid Catalyst: Synthesis, Dynamic NMR, Asymmetric Catalysis, and Theoretical Studies

Cited by 75 publications

References 81 publications

The Bis(pentafluoroethyl)phosphinous Acid (C₂F₅)₂POH

The Bis(pentafluoroethyl)phosphinous Acid (C₂F₅)₂POH

Synthesis of the First Chiral Bidendate Bis(trifluoromethyl)phosphane Ligand through Stabilization of the Bis(trifluoromethyl)phosphanide Anion in the Presence of Acetone

Cationic Chiral Dirhodium Carboxamidates Are Activated for Lewis Acid Catalysis

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[CpRu((R)-Binop-F)(H2O)][SbF6], a New Fluxional Chiral Lewis Acid Catalyst: Synthesis, Dynamic NMR, Asymmetric Catalysis, and Theoretical Studies

Cited by 75 publications

References 81 publications

The Bis(pentafluoroethyl)phosphinous Acid (C2F5)2POH

The Bis(pentafluoroethyl)phosphinous Acid (C2F5)2POH

Synthesis of the First Chiral Bidendate Bis(trifluoromethyl)phosphane Ligand through Stabilization of the Bis(trifluoromethyl)phosphanide Anion in the Presence of Acetone

Cationic Chiral Dirhodium Carboxamidates Are Activated for Lewis Acid Catalysis

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[CpRu((R)-Binop-F)(H₂O)][SbF₆], a New Fluxional Chiral Lewis Acid Catalyst: Synthesis, Dynamic NMR, Asymmetric Catalysis, and Theoretical Studies

The Bis(pentafluoroethyl)phosphinous Acid (C₂F₅)₂POH

The Bis(pentafluoroethyl)phosphinous Acid (C₂F₅)₂POH