Highly Efficient and Versatile Phosphine‐Phosphoramidite Ligands for Asymmetric Hydrogenation

Eggenstein, Matthias; Thomas, Anika; Theuerkauf, Jens; Franciò, Giancarlo; Leitner, Walter

doi:10.1002/adsc.200800653

Cited by 79 publications

(33 citation statements)

References 21 publications

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“…Very recently, Franciò and Leitner reported a set of novel phosphinephosphoramidite ligands 48 possessing two elements of chirality prepared through a modular synthetic approach (Figure 9.12). The ligands bearing (S)-central and (S)-axial chiralities are unique in providing enantioselectivities (>99% ee) in the Rhcatalyzed asymmetric hydrogenation of the model substrate 4a [52].…”

Section: Unsymmetrical Hybrid Phosphorus-containing Ligands For Rh-camentioning

confidence: 99%

Bidentate Ligands for Enantioselective Enamide Reduction

Zheng

2010

Chiral Amine Synthesis

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Scheme 9.1 The first catalytic asymmetric hydrogenation of enamide 1a reported by Kagan.Scheme 9.2 General methods for the synthesis of N-acyl-a-arylenamides. 274j 9 Bidentate Ligands for Enantioselective Enamide Reduction R O Scheme 9.4 Synthesis of exocyclic enamides. 9.2 Catalytic Enantioselective Hydrogenation of Enamides j275 4 15 Scheme 9.11 Rh-catalyzed asymmetric hydrogenation of ortho-substituted arylenamides with a triphosphorus bidentate phosphine-phosphoramidite ligand 49. 288j 9 Bidentate Ligands for Enantioselective Enamide Reduction P P P P Me-DuPhos Me-BPE 61 Scheme 9.15 Asymmetric hydrogenation of tetra-substituted cyclic enamides using the Ru-catalyst containing Me-DuPHOS or Me-BPE. 9.2 Catalytic Enantioselective Hydrogenation of Enamides j291

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Section: Unsymmetrical Hybrid Phosphorus-containing Ligands For Rh-camentioning

confidence: 99%

Bidentate Ligands for Enantioselective Enamide Reduction

Zheng

2010

Chiral Amine Synthesis

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“…These ligands proved to be very efficient for asymmetry of 2-substituted quinolines [22]. The hydrogenation reaction proceeded smoothly with up to 97% ee and full conversion (Scheme 10.16).…”

mentioning

confidence: 94%

Enantioselective Reduction of Nitrogen‐Based Heteroaromatic Compounds

Wang

Zhou

Wang

2010

Chiral Amine Synthesis

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Optically active amines are fundamentally important synthetic intermediates and structural components of biologically active natural products, drugs, and pharmaceuticals. Asymmetric hydrogenation of nitrogen-based heteroaromatic compounds is one of the most attractive and efficient approaches to enantiomerically pure amines, especially for numerous saturated or partially saturated chiral cyclic amines, whose synthesis by direct cyclization is often difficult. In the past decades, some progresses have been achieved in the hydrogenation of nitrogen-containing heteroaromatic compounds [1]. For example, quinolines, quinoxalines, pyridines, indoles, and pyrroles have been hydrogenated successfully with over 90% enantiomeric excess (ee). In this chapter, we focus on the synthesis of chiral amines via enantioselective hydrogenation of nitrogen-based heteroaromatic compounds. Asymmetric Hydrogenation of Quinolines Ir-and Ru-Catalyzed Asymmetric Hydrogenation of QuinolinesAmong these studies on asymmetric hydrogenation of nitrogen-based heteroaromatic compounds, the hydrogenation of quinolines was studied extensively and elaborately. In 2003, Zhou and coworkers reported the first highly enantioselective hydrogenation of quinolines with high enantioselectivities [2]. They employed [Ir(COD)Cl] 2 /MeO-BiPhep as catalyst using iodine as additive, while the hydrogenation reaction could not take place in the absence of iodine. Their studies showed that this reaction was highly solvent dependent, and toluene was the best solvent.Subsequently, some commercially available chiral bidentate phosphine ligands were tested for the asymmetric hydrogenation of quinolines, and (S)-MeO-BiPhep was the best ligand with 94% ee (Scheme 10.1). The optimal conditions are [Ir(COD) Cl] 2 /MeO-BiPhep/I 2 in toluene at 700 psi H 2 .

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“…Since then, a rapidly increasing number of effective ligands have been introduced by other groups 3f. j, 4f, g, 9, 10 Other approaches to activate the substrate have also been reported. Zhou studied chloroformate as activators, which acted by the formation of quinolinium and isoquinolinium salts in situ; these salts were then smoothly hydrogenated 3c.…”

Section: Introductionmentioning

confidence: 99%

Additive Effects of Amines on Asymmetric Hydrogenation of Quinoxalines Catalyzed by Chiral Iridium Complexes

Nagano

Iimuro

Schwenk

et al. 2012

Chemistry A European J

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The additive effects of amines were realized in the asymmetric hydrogenation of 2-phenylquinoxaline, and its derivatives, catalyzed by chiral cationic dinuclear triply halide-bridged iridium complexes [{Ir(H)[diphosphine]}(2)(μ-X)(3)]X (diphosphine = (S)-2,2'-bis(diphenylphosphino)-1,1'-binaphthyl [(S)-BINAP], (S)-5,5'-bis(diphenylphosphino)-4,4'-bi-1,3-benzodioxole [(S)-SEGPHOS], (S)-5,5'-bis(diphenylphosphino)-2,2,2',2'-tetrafluoro-4,4'-bi-1,3-benzodioxole [(S)-DIFLUORPHOS]; X = Cl, Br, I) to produce the corresponding 2-aryl-1,2,3,4-tetrahydroquinoxalines. The additive effects of amines were investigated by solution dynamics studies of iridium complexes in the presence of N-methyl-p-anisidine (MPA), which was determined to be the best amine additive for achievement of a high enantioselectivity of (S)-2-phenyl-1,2,3,4-tetrahydroquinoxaline, and by labeling experiments, which revealed a plausible mechanism comprised of two cycles. One catalytic cycle was less active and less enantioselective; it involved the substrate-coordinated mononuclear complex [IrHCl(2)(2-phenylquinoxaline){(S)-BINAP}], which afforded half-reduced product 3-phenyl-1,2-dihydroquinoxaline. A poorly enantioselective disproportionation of this half-reduced product afforded (S)-2-phenyl-1,2,3,4-tetrahydroquinoxaline. The other cycle involved a more active hydride-amide catalyst, derived from amine-coordinated mononuclear complex [IrCl(2)H(MPA){(S)-BINAP}], which functioned to reduce 2-phenylquinoxaline to (S)-2-phenyl-1,2,3,4-tetrahydroquinoxaline with high enantioselectivity. Based on the proposed mechanism, an Ir(I)-JOSIPHOS (JOSIPHOS = (R)-1-[(S(p))-2-(dicyclohexylphosphino)ferrocenylethyl]diphenylphosphine) catalyst in the presence of amine additive resulted in the highest enantioselectivity for the asymmetric hydrogenation of 2-phenylquinoxaline. Interestingly, the reaction rate and enantioselectivity were gradually increased during the reaction by a positive-feedback effect from the product amines.

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Highly Efficient and Versatile Phosphine‐Phosphoramidite Ligands for Asymmetric Hydrogenation

Abstract: A set of novel phosphine-phosphoramidite ligands possessing two elements of chirality have been prepared through a modular synthetic approach.

Cited by 79 publications

References 21 publications

Bidentate Ligands for Enantioselective Enamide Reduction

Bidentate Ligands for Enantioselective Enamide Reduction

Enantioselective Reduction of Nitrogen‐Based Heteroaromatic Compounds

Additive Effects of Amines on Asymmetric Hydrogenation of Quinoxalines Catalyzed by Chiral Iridium Complexes

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