Phospholane–Oxazoline Ligands for Ir‐Catalyzed Asymmetric Hydrogenation

Tang, Wenjun; Wang, Weimin; Zhang, Xumu

doi:10.1002/ange.200390220

Cited by 35 publications

(3 citation statements)

References 31 publications

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“…Having been unsuccessful in generating an unsubstituted phospholane, we decided to try to further functionalize phospholane 8 a . Reactions at the α‐carbon of borane‐protected phosphanes (BisP*)28 and sulfur‐protected phospholanes (TangPhos)9b, 29 have been reported. However, when we applied the reported conditions to borane‐protected 8 a , no reaction was observed, regardless of the base or electrophile used.…”

Section: Resultsmentioning

confidence: 99%

P‐Chiral Ferrocenephospholanes: Synthesis, Reactivity, Metal Complex Chemistry and Application in the Asymmetric Hydrogenation of Olefins

Gschwend

Pugin²,

Bertogg³

et al. 2009

Chemistry A European J

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Starting from (R)-N,N-dimethyl-1-ferrocenylethylamine, a diastereoselective ortho-lithiation procedure and a stereoconvergent intramolecular hydrophosphination gave access to P-chiral ferrocenephospholanes. These mono- or bidentate ligands were converted to the corresponding rhodium and iridium complexes, including a chiral version of Crabtree's catalyst, and tested in the asymmetric hydrogenation of functionalized and unfunctionalized olefins. A significant reactivity difference between the rhodium-1,5-cyclooctadiene and the rhodium-norbornadiene complex was observed during catalyst activation.

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Section: Resultsmentioning

confidence: 99%

P‐Chiral Ferrocenephospholanes: Synthesis, Reactivity, Metal Complex Chemistry and Application in the Asymmetric Hydrogenation of Olefins

Gschwend

Pugin²,

Bertogg³

et al. 2009

Chemistry A European J

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“…A phospholane-oxazoline hybrid ligand was developed by Zhang et al for the Ir-catalyzed asymmetric hydrogenation of non-or less functionalized olefins (Scheme 3.65) [154]. Application of these ligands in the catalytic reaction gave good and excellent enantioselectivities (77-99 %ee.…”

Section: Bidentate Mono(phospholanes) Bearing a Second Ligating Non-pmentioning

confidence: 99%

Synthesis of Chiral Heterocyclic Phosphines for Application in Asymmetric Catalysis

Holz¹,

Gensow²,

Zayas

et al. 2007

COC

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“…Thus, using Crabtree's catalyst A as a conceptual template,4 Pfaltz and co‐workers pioneered the application of ligands with N,P‐coordinating groups5–7 in this area, particularly in phosphine oxazoline complexes like B 6. 8–14 Others,14–16 including our group,17 subsequently designed and tested similar complexes. More recently, studies from our laboratories demonstrated that N ‐heterocyclic carbene–oxazoline ligands like C also could be used to reduce tri‐ and disubstituted arylalkenes with good conversions and enantioselectivities 18.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Insights into Iridium‐Catalyzed Asymmetric Hydrogenation of Dienes

Cui

Fan

Hall

et al. 2005

Chemistry A European J

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Hydrogenation of 2,3-diphenylbutadiene (1) with the chiral carbene-oxazoline-iridium complex C has been studied by means of a combined experimental and computational approach. A detailed kinetic profile of the reaction was obtained with respect to consumption of the substrate and formation of the intermediate half-reduction products, 2,3-diphenylbut-1-ene (2) and the final product, 2,3-diphenylbutane (3). The data generated from these analyses, and from NMR experiments, revealed several facets of the reaction. After a brief induction period (presumably involving reduction of the cyclooctadiene ligand on C), the diene concentration declines in a zero-order process primarily to give monoene intermediates. When all the diene is consumed, the reaction accelerates and compound 3 begins to accumulate. Interestingly, the prevalent enantiomer of the monoene intermediate 2 is converted mostly to meso-3 so the enantioselectivity of the reaction appears to reverse. The reaction seems to be first-order with respect to the catalyst when the catalyst concentration is less than 0.0075 M; diffusion of hydrogen across the gas-liquid interface complicates the analysis at higher catalyst concentrations. Similarly, these diffusion effects complicated measurements of reaction rate versus applied pressure of dihydrogen; other factors like stir speed and flask geometry come into play under some, but not all, the conditions examined. Density functional theory (DFT) calculations, using the PBE method, were used to probe the reaction. These studies indicate a transoid-eta(4)-diene-dihydride complex forms in the first stages of the catalytic cycle. Further reaction requires dissociation of one alkene ligand to give a eta(2)-diene-dihydride-dihydrogen intermediate. A catalytic cycle that features Ir(3+)/Ir(5+) seems to be involved thereafter.

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Phospholane–Oxazoline Ligands for Ir‐Catalyzed Asymmetric Hydrogenation

Abstract: Eine neue Klasse chiraler Phospholan‐Oxazolin‐Liganden (P*) ermöglicht hohe Enantioselektivitäten in der Ir‐katalysierten asymmetrischen Hydrierung von Methylstilbenderivaten und (E)‐β‐Methylzimtsäureestern (siehe Schema; z. B. R=Ph, Ar=m‐CH3C6H4).

Cited by 35 publications

References 31 publications

P‐Chiral Ferrocenephospholanes: Synthesis, Reactivity, Metal Complex Chemistry and Application in the Asymmetric Hydrogenation of Olefins

P‐Chiral Ferrocenephospholanes: Synthesis, Reactivity, Metal Complex Chemistry and Application in the Asymmetric Hydrogenation of Olefins

Synthesis of Chiral Heterocyclic Phosphines for Application in Asymmetric Catalysis

Mechanistic Insights into Iridium‐Catalyzed Asymmetric Hydrogenation of Dienes

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