Chiral iridium(I) bis(NHC) complexes as catalysts for asymmetric transfer hydrogenation

Diez, Claus; Nagel, Ulrich

doi:10.1002/aoc.1650

Cited by 43 publications

(21 citation statements)

References 23 publications

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“…For clarity, the hydrogen atoms are omitted and the cis,cis-1,5-cyclooctadiene ligands are represented as lines. Selected bond lengths (Å) and angles (deg): C1−N1, 1.360(8); C1−N2, 1.351(8); C2−N1, 1.369(8); C3−N2, 1.387(9); C2−C3, 1.306(10); C4−N1, 1.462(8); C13−N2, 1.474(9); C1−Ir1, 2.085(7); Cl1−Ir2, 2.352 (2); N1−C1−N2, 103.8(6); N2−C13−C14, 111.4(6).…”

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Cationic Iridium Complexes Containing Anionic Iridium Counterions Supported by Redox-Active N-Heterocyclic Carbenes

et al. 2013

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The first cationic iridium complex supported by two bulky, ferrocenylated N-heterocyclic carbenes, [(1) 2 Ir-(COD)] + [Cl] − ([2] + [Cl] − ; 1 = 1-ferrocenylmethyl-3-mesitylimidazol-2-ylidene, Fc-NHC; COD = cis,cis-1,5-cyclooctadiene), was synthesized and characterized. Treatment of the aforementioned complex with a mixture of [N(nBu) 4 ] + [Cl] − and [Ir(COD)(Cl)] 2 afforded [(1) 2 Ir(COD)] + [Ir(COD)-(Cl) 2 ] − ([2] + [Ir(COD)Cl 2 ] − ), which featured cationic as well as anionic Ir centers. Electrochemical analysis of [2] + [Ir(COD)Cl 2 ] − revealed that the complex displayed two reversible (iron-and iridium-centered) and two irreversible (iridium-centered) redox processes, which were assigned to the cationic and anionic components, respectively. Stirring [2] + [Ir(COD)Cl 2 ] − under an atmosphere of carbon monoxide generated the corresponding Ir carbonyl complex [(1) 2 Ir(CO) 2 ] + [Ir(CO) 2 (Cl) 2 ] − ([3] + [Ir(CO) 2 Cl 2 ] − ). Cyclic voltammetry (CV) measurements of the aforementioned complexes containing [(1) 2 Ir(COD)] + showed that the iron-centered oxidations were concurrent, reflective of limited electronic coupling between the two ferrocenyl moieties. However, spectroelectrochemical analysis of [(1) 2 Ir(CO) 2 ] + [BAr F 4 ] − revealed that the electron density at the Ir centers supported by the Fc-NHC ligands decreased upon oxidation of the ferrocenyl groups, as evidenced by a ca. 10 cm −1 increase in the recorded ν CO bands.

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“…] + [PF6 ] − (0.1 M) as the electrolyte. The time-dependent and steady-state currents, i(t) and i ss , respectively, were measured by increasing the potential from 0 to 0.4 V (holding at 0.4 V for 10 s).…”

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Cationic Iridium Complexes Containing Anionic Iridium Counterions Supported by Redox-Active N-Heterocyclic Carbenes

et al. 2013

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“…N-Heterocyclic carbenes, either generated in situ from the ligand and the complex [IrCl 2 Cp*] 2 or already prepared, such in the case of complexes 64, 66 65 67 and 66, 68 were used in the ATH of phenones with variable results. Similarly, the two sulphurcontaining ligands 67 69 and 68 70 were efficient in the ATH of aromatic and heterocyclic ketones using different iridium(I) complexes as metallic components and isopropanol as the hydrogen source.…”

Section: Iridium Catalystsmentioning

confidence: 99%

Catalytic asymmetric transfer hydrogenation of ketones: recent advances

Foubelo

Nájera

Yus

2015

Tetrahedron: Asymmetry

205

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Abstract-In this review article we will consider the main processes on asymmetric transfer hydrogenation (ATH) of ketones from 2008 up today. The most effective organometallic compounds (derived from Ru, Rh, Ir, Fe, Os, Ni, Co, and Re) and chiral ligands (derived from amino alcohols, diamines, sulphur-and phosphorous-containing compounds, as well as heterocyclic systems) will be shown paying special attention to functionalized substrates, tandem reactions, processes under nonconventional conditions, supported catalysts, dynamic kinetic resolutions (DKR), the use of water as a green solvent, theoretical and experimental studies on reaction mechanisms, enzymatic processes and finally applications to the total synthesis of biologically active organic molecules. _____________________________________________________________________________________

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“…For this reason, the scientific community has been directing considerable research effort into catalytic transfer hydrogenation, [6][7][8] which favors use of hydrogen donors (alcohols, diimides, amines, hydrocarbons or formic acid) and avoids molecular hydrogen. Ruthenium, 9-11 rhodium, [12][13][14][15] iridium, [16][17][18][19] and nickel 20 are the metals most frequently used as catalysts. Organocatalytic transfer hydrogenation using dihydropyridines as hydride donors and Brönsted acid catalysis has also been intensively investigated.…”

Section: Introductionmentioning

confidence: 99%

Triazolopyridines. Part 30. Hydrogen transfer reactions; pyridylcarbene formation

Abarca

Adam²,

Alom³

et al. 2013

Arkivoc

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The transfer hydrogenation reaction of [1,2,3]triazolo [1,5-a]pyridines with Pd/C/Zn or Pd(OH) 2 /C/Zn in water, ethanol or water/ethanol mixture has been explored. 4,5,6,7-Tetrahydrotriazolopyridines were obtained in good to medium yields. In addition, under the same conditions 2-substituted pyridines were also formed as a result of intermediate pyridylcarbene formation, by triazole ring opening and loss of nitrogen.

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Chiral iridium(I) bis(NHC) complexes as catalysts for asymmetric transfer hydrogenation

Cited by 43 publications

References 23 publications

Cationic Iridium Complexes Containing Anionic Iridium Counterions Supported by Redox-Active N-Heterocyclic Carbenes

Cationic Iridium Complexes Containing Anionic Iridium Counterions Supported by Redox-Active N-Heterocyclic Carbenes

Catalytic asymmetric transfer hydrogenation of ketones: recent advances

Triazolopyridines. Part 30. Hydrogen transfer reactions; pyridylcarbene formation

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