C2 and C1 Symmetry of chiral auxiliaries in catalytic reactions on metal complexes

Павлов, В. А.

doi:10.1016/j.tet.2007.10.078

Cited by 47 publications

(12 citation statements)

References 420 publications

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“…However, to date, there has not been a substantial reason why a C 2 ‐symmetric ligand should necessarily be superior to a nonsymmetric counterpart. In contrast, good arguments have recently surfaced suggesting that nonsymmetrical ligands provide a more effective enantiocontrol than C 2 ‐symmetric ligands for certain reactions 5. Also noteworthy, the idea that C 1 ‐symmetric phosphite‐type compounds with P *‐stereocenters still remain as relatively rare class of chiral inductors 6–13.…”

Section: Introductionmentioning

confidence: 99%

(S)‐6‐Bromo‐BINOL‐based phosphoramidite ligand with C₁ symmetry for enantioselective hydrogenation and allylic substitution

et al. 2010

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(S)-6-Br-BINOL-derived phosphoramidite, a simple monodentate ligand with a stereogenic center at the phosphorus atom, was synthesized for the first time. This stereoselector generated a high level of enantioselectivity (80-95% ee) in the rhodium-catalyzed hydrogenation of alpha-dehydrocarboxylic acid esters and was also successfully employed in the asymmetric palladium-catalyzed allylic substitution of (E)-1,3-diphenylallyl acetate. The optical yield also showed significant dependence with reaction type: up to 70% ee for allylic amination, up to 75% ee for allylic sulfonylation, and up to 90% ee for allylic alkylation.

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Section: Introductionmentioning

confidence: 99%

(S)‐6‐Bromo‐BINOL‐based phosphoramidite ligand with C₁ symmetry for enantioselective hydrogenation and allylic substitution

et al. 2010

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“…As a consequence, the number of interactions with a substrate is reduced compared to that of a catalyst devoid of symmetry. As pointed out by Pavlov,28 catalytically active species frequently have asymmetric structures; the role of the homotopic groups or faces present in a symmetric ligand is then to reduce the number of the these complexes. The examples given in this overview illustrate that besides symmetry, electronic and steric factors may be important for the enantioselectivity and these factors often outperform the effect of symmetry.…”

Section: Discussionmentioning

confidence: 99%

“…Of even higher interest are results obtained from ligands with mixed substitution patterns, 7a – d : in Cu(I)‐catalyzed cyclopropanations the asymmetric ligands, with both isopropyl and tert ‐butyl substituents, proved to lead to higher selectivity than those with only one type of substituents (Table 5),19 demonstrating that rotational symmetry does not necessarily lead to improved stereoselectivity 28…”

Section: Distorting the Symmetrymentioning

confidence: 99%

The Role of Symmetry in Asymmetric Catalysis

Moberg

2012

Israel Journal of Chemistry

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Chiral ligands and metal complexes with rotational (Cn, Dn) symmetry often have beneficial properties in asymmetric catalysis. The enhanced enantioselectivity frequently observed is a result of a reduction of competing reaction routes. This may be due to rotational symmetry in the catalyst, leading to a limited number of different catalyst‐substrate interactions, or to formation of a limited number of catalytic species as a result of rotational symmetry in the ligand. The effect of symmetry is usually difficult to evaluate, since a change in symmetry properties necessarily is accompanied by structural modifications. In each situation the number of intermediate complexes, their electronic and steric properties, and their energy need to be analyzed. Although other factors may be more important than symmetry for achieving high enantioselectivity, a vast number of C2‐ and to some extent C3‐symmetric ligands have been found to have excellent properties in asymmetric catalysis, providing products with high enantiomeric purity. Besides the benefit of symmetry in the ligand and catalyst, the symmetry of the substrate may be important since a gain in enantioselectivity can result from simultaneous asymmetric transformations of homotopic functional groups.

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“…Catalytic reactions were run with 20 mol% of (BINOLate)Ti(O-i-Pr) 2 and 80 mol% of titanium tetraisopropoxide. The stoichiometric reaction were performed using 100 mol% of (BINOLate)Ti(O-i-Pr) 2 .…”

Section: Ohmentioning

confidence: 99%

“…Curie [1] was convinced that "without asymmetric physical impact no asymmetric chemical effect arises". Modern experimental data support this criterion: asymmetric induction in asymmetric catalysis is only implemented through the asymmetric (C 1 symmetry axis) key intermediate [2].…”

Section: Introductionmentioning

confidence: 99%

Сhiral and Racemic Fields Concept for Understanding of the Homochirality Origin, Asymmetric Catalysis, Chiral Superstructure Formation from Achiral Molecules, and B-Z DNA Conformational Transition

2019

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The four most important and well-studied phenomena of mirror symmetry breaking of molecules were analyzed for the first time in terms of available common features and regularities. Mirror symmetry breaking of the primary origin of biological homochirality requires the involvement of an external chiral inductor (environmental chirality). All reviewed mirror symmetry breaking phenomena were considered from that standpoint. A concept of chiral and racemic fields was highly helpful in this analysis. A chiral gravitational field in combination with a static magnetic field (Earth’s environmental conditions) may be regarded as a hypothetical long-term chiral inductor. Experimental evidences suggest a possible effect of the environmental chiral inductor as a chiral trigger on the mirror symmetry breaking effect. Also, this effect explains a conformational transition of the right-handed double DNA helix to the left-handed double DNA helix (B-Z DNA transition) as possible DNA damage.

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C2 and C1 Symmetry of chiral auxiliaries in catalytic reactions on metal complexes

Cited by 47 publications

References 420 publications

(S)‐6‐Bromo‐BINOL‐based phosphoramidite ligand with C₁ symmetry for enantioselective hydrogenation and allylic substitution

(S)‐6‐Bromo‐BINOL‐based phosphoramidite ligand with C₁ symmetry for enantioselective hydrogenation and allylic substitution

The Role of Symmetry in Asymmetric Catalysis

Сhiral and Racemic Fields Concept for Understanding of the Homochirality Origin, Asymmetric Catalysis, Chiral Superstructure Formation from Achiral Molecules, and B-Z DNA Conformational Transition

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C2 and C1 Symmetry of chiral auxiliaries in catalytic reactions on metal complexes

Cited by 47 publications

References 420 publications

(S)‐6‐Bromo‐BINOL‐based phosphoramidite ligand with C1 symmetry for enantioselective hydrogenation and allylic substitution

(S)‐6‐Bromo‐BINOL‐based phosphoramidite ligand with C1 symmetry for enantioselective hydrogenation and allylic substitution

The Role of Symmetry in Asymmetric Catalysis

Сhiral and Racemic Fields Concept for Understanding of the Homochirality Origin, Asymmetric Catalysis, Chiral Superstructure Formation from Achiral Molecules, and B-Z DNA Conformational Transition

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(S)‐6‐Bromo‐BINOL‐based phosphoramidite ligand with C₁ symmetry for enantioselective hydrogenation and allylic substitution

(S)‐6‐Bromo‐BINOL‐based phosphoramidite ligand with C₁ symmetry for enantioselective hydrogenation and allylic substitution