Asymmetric Catalysis with the Normally Unresolvable, Conformationally Dynamic 2,2‘-Bis(diphenylphosphino)-1,1‘-biphenyl (Biphep)

Becker, Jennifer J.; White, Peter S.; Gagné, Michel R.

doi:10.1021/ja016167p

Cited by 103 publications

(47 citation statements)

References 9 publications

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“…After performing a similar dynamic resolution as the above method, protonolysis of the BINOL ligand gave the (BIP-HEP)Pt II dication, which was used as a highly enantioselective Lewis acid catalyst in the asymmetric Diels-Alder reaction [34].…”

Section: Introductionmentioning

confidence: 99%

Resolution of BIPHEP on Rh with a chiral diene auxiliary

Faller

Wilt

2006

Journal of Organometallic Chemistry

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Section: Introductionmentioning

confidence: 99%

Resolution of BIPHEP on Rh with a chiral diene auxiliary

Faller

Wilt

2006

Journal of Organometallic Chemistry

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“…In the light of this perception it looks promising to attach, for example, donor substituted configurationally labile biphenyl units to the polymer to obtain rapidly interconverting, conformationally diastereomeric catalysts with the metal determining the stereochemical outcome of the reaction. This can be provoked either by locking an induced preferred conformation by metal complexation (33,34) or by preferred reaction of one diastereomorphic conformation (32).…”

Section: Resultsmentioning

confidence: 99%

Helically chiral polymers: A class of ligands for asymmetric catalysis

Reggelin

Doerr

Klußmann

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

145

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Helically chiral polymers from achiral monomers containing N and P atoms have been shown to be ligands for transition metals such as Pd and Rh. The Rh complex of the phosphane-containing polyisocyanate p(18-co-17) was an active albeit hardly enantioselective catalyst in the asymmetric hydrogenation of the dehydro amino acid N-acetamidocinnamic acid (15% enantiomeric excess). The most active catalyst obtained until now was the Pd-complexed polymethacrylate Pd-p12, which catalyzes the allylic substitution reaction of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate even at ؊20°C in quantitative yield, although again the enantioselectivity was unsatisfactory. The most successful application of a helically chiral polymer in asymmetric catalysis with respect to both reactivity and enantioselectivity is the polymethacrylate p(5-co-8). Its palladium complex catalyzes the above-mentioned reaction at 0°C with quantitative yield and 60% enantiomeric excess.polymethacrylate ͉ polyisocyanate ͉ helicity ͉ polymeric ligand ͉ chiral catalyst S oluble chiral polymers may be promising ligands in asymmetric transition metal catalysis for a number of reasons. The reisolation of the mostly expensive chiral catalyst by precipitation or ultrafiltration should be easy, while all of the analytical and kinetic advantages of a reaction in homogeneous phase should be maintained. Moreover, there might be a number of beneficial effects related to the macromolecular state, for example cooperativity or chiral amplification as observed in polyisocyanates (1). These advantages may allow for the synthesis of novel catalysts with properties not achievable with micromolecular systems.The most obvious way to prepare macromolecular metal catalysts is to attach well known, catalytically active chiral components to soluble polymers. To get equal asymmetric inductions from each active site, the microenvironments of the complexed metal atoms must be uniform. This uniformity can be achieved either by attaching only one metal-binding site per polymer chain or by complexing several transition metals by a stereoregular polymer. The former strategy was realized rather successfully in the asymmetric dihydroxylation reaction with MeO-polyethylene glycolbound chiral ligands described by Bolm and Gerlach (2) and Han and Janda (3). However, the major disadvantage of this approach is the very low density of reactive centers per unit mass. A successful example for the second strategy is the application of polybinaphthol complexes as catalysts as exemplified by Pu (4). Problems associated with the latter ligands include the necessity to prepare the enantiomerically pure monomers and the question of potential counterproductive interactions of the different sources of chirality (axial chirality of the monomers and helical chirality of the polymer). Indeed, we think that for the phosphane-modified helical chiral dodecapeptides developed by Gilbertson and Wang (5) the major reason for their failure to achieve good enantioselectivities in asymmetric hydrogenation r...

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“…We are not the first to assert this claim; several research groups were cognizant of or invoked ligand distortions as being responsible for stereoinduction in Jacobsen-Katsuki-type catalysts, 11,[13][14][15][16][17] bisoxazolinyl-type catalysts, [18][19][20] porphyrins, 21,22 biaryls, [23][24][25] and there are examples in the literature where flexible ligands can be locked into an asymmetric shape so that good ee's are noted. [26][27][28][29][30] The difference between these studies and ours is that we can quantify how much chirality is associated with each of these distortions. In this article we report on several distortion modes available to this ligand and demonstrate that one or more such modes can significantly increase the chirality content of this catalyst.…”

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confidence: 79%

Ligand distortion modes leading to increased chirality content of Katsuki‐Jacobsen catalysts

Lipkowitz

Schefzick

2002

Chirality

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The "chirality content" of Katsuki-Jacobsen epoxidation catalysts are computed with the Avnir continuous chirality measure (CCM). An assessment of Mn(salen) molecules from the Cambridge Structural Database shows there exist some variation in CCM and the chirality content for several triplet state complexes of these catalysts purported in the literature to be the active species show even larger CCM values. Several deformation modes were analyzed to examine how chirality content changes as catalyst distortion is induced. The deformations studied include in-plane deformations, cup-shaped puckering, ligand twisting motions, and step-like deformations. Some distortions lead to increases of chirality while others lead to a decrease in chirality content. The most influential distortion modes that can be used for ligand design are twisting and step induction.

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Asymmetric Catalysis with the Normally Unresolvable, Conformationally Dynamic 2,2‘-Bis(diphenylphosphino)-1,1‘-biphenyl (Biphep)

Cited by 103 publications

References 9 publications

Resolution of BIPHEP on Rh with a chiral diene auxiliary

Resolution of BIPHEP on Rh with a chiral diene auxiliary

Helically chiral polymers: A class of ligands for asymmetric catalysis

Ligand distortion modes leading to increased chirality content of Katsuki‐Jacobsen catalysts

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