From Prochiral N-Heterocyclic Carbenes to Optically Pure Metal Complexes: New Opportunities in Asymmetric Catalysis

Kong, Lingyu; Morvan, Jennifer; Pichon, Delphine; Jean, Marion; Albalat, Muriel; Vivès, Thomas; Colombel‐Rouen, Sophie; Giorgi, Michel; Dorcet, Vincent; Roisnel, Thierry; Crévisy, Christophe; Nuel, Didier; Nava, Paola; Humbel, Stéphane; Vanthuyne, Nicolas; Mauduit, Marc; Clavier, Hervé

doi:10.1021/jacs.9b12698

Cited by 48 publications

(42 citation statements)

References 28 publications

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“…Owing to the good stability of NHC-metal complexes towards purification by silica gel chromatography, enantiomers resolutions could be achieved using chiral high-performance liquid chromatography (HPLC) in preparative scale (up to 600-mg scale). 22 C 2 -symmetric Pd-and Cu-IKong complexes exhibited good performances in asymmetric catalysis with chiral inductions exceeding 90% ee. Even if C 1 -symmetric Cu-IKong complexes gave good results in copper-catalyzed asymmetric allylic alkylation, these dissymmetric NHC ligands are interesting to accurately investigate their configurational stability, in particular the values of rotational barriers of the NHC-metal complexes.…”

Section: Introductionmentioning

confidence: 99%

Transition metal complexes bearing atropisomeric saturated NHC ligands

et al. 2021

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From achiral imidazolinium salts, chiral transition metal complexes containing an N-heterocyclic carbene (NHC) ligand were prepared (metal = palladium, copper, silver, gold, rhodium). Axial chirality in these complexes results from the formation of the metal-carbene bond leading to the restriction of rotation of dissymmetric N-aryl substituents about the C-N bond. When these complexes exhibited a sufficient configurational stability, a resolution by chiral highperformance liquid chromatography (HPLC) on preparative scale enabled isolation of enantiomers with excellent enantiopurities (>99% ee) and good yields. A study of the enantiomerization barriers revealed the effect of the backbone nature as well as the type of transition metal on its values. Nevertheless, the evaluation of palladium-based complexes in asymmetric intramolecular α-arylation of amides demonstrated that the ability to induce an enantioselectivity cannot be correlated to the configurational stability of the precatalysts.

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Section: Introductionmentioning

confidence: 99%

Transition metal complexes bearing atropisomeric saturated NHC ligands

et al. 2021

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“…The 1 H NMR spectra of complexes 9 and 10 are somewhat intricate due to the presence of at least two isomeric forms. For the same reason, 13 C NMR spectra show a multitude of peaks, but characteristic carbenic carbons were observable in the range 178-182 ppm. [17]…”

Section: Palladium Complexes Preparation and Resolutionmentioning

confidence: 99%

C₁‐Symmetric Atropisomeric NHC Palladium(II) Complexes: Synthesis, Resolution and Characterization

et al. 2021

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Series of chiral palladium(II) allyl and cinnamyl complexes bearing a C 1 -symmetric N-heterocyclic carbenes were synthesized from achiral precursors. The chirality of theses complexes results from the formation of the carbene-palladium bond which restricts the rotation of dissymmetric N-aryl substituents of the NHC and thus creates an axis of chirality. Chiral HPLC at preparative scale enabled the resolution of racemic complexes and provided a straightforward access to complexes with excellent enantiopurities (> 99.5% ee). Enantiopure complexes were studied by crystal X-ray diffraction and electronic circular dichroism (ECD). Their configuration stabilities were investigated both experimentally and theoretically through the determination of the rotational barrier values. These complexes were tested for the intramolecular α-arylation of amides, with a moderate chiral induction (up to 54% ee).

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“…Two theoretically possible mechanisms of such processes have been considered: the monomolecular dissociative and the bimolecular associative ones (Scheme 50, a and b, respectively) [230]. The monomolecular mechanism suggests the dissociation of NHC-M C complex with the formation of free carbene, which is then bound to the other metal, affording the transmetalation product.…”

Section: Possible Mechanisms and Driving Forces Of Transmetalation And Related Processesmentioning

confidence: 99%

“…The reaction of the chiral carbene copper complexes (NHC)CuCl with compounds of other metals under conditions of transmetalation reactions has been recently investigated in the study [230] Hence, basing on the data from that and other studies discussed in this review, the associative mechanism occurring via the formation of the NHC-bridged heterometallic transition states or intermediates seems to be more plausible. Remarkably, the formation of multinuclear N-heterocyclic carbene complexes with two bridging NHC is also possible [244].…”

Section: Possible Mechanisms and Driving Forces Of Transmetalation And Related Processesmentioning

confidence: 99%

Alternative Transformations of N-Heterocyclic Carbene Complexes of the Group 11 Metals in Transmetalation Reactions (A Review)

Mikhaylov

Балова

2021

Russ J Gen Chem

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The carbene transfer from N-heterocyclic carbene complexes of Group 11 metals (NHC-M C ) (especially silver and copper) to other metals is considered a convenient and universal, sometimes having no alternative, method for the synthesis of a wide range of important N-heterocyclic carbene complexes of transition metals. As the number of successful examples of transmetalation with the formation of the target product has increased, the data were accumulated on alternative or unexpected results of the interaction of NHC-M C complexes with compounds of other metals. This review considers the examples of NHC-M C reactions with compounds of other metals which proceed with a change in the metals oxidation state, conversion of (NHC)M C X into cationic homoleptic [(NHC) 2 M C ] + forms, transmetalation retaining the other metal in the coordination sphere of the product, or formation of heterometallic adducts preserving the M C -C carbene bond, rather than these occurring according to the standard reaction pathway. Unusual "reverse" carbene transfer reactions have been considered separately. The review material reveals a promising new synthetic potential of NHC-M C in the reactions with other metals and discusses the possible mechanisms and driving forces of such transformations. The most important aspects of the application of the obtained products, primarily in various catalytic processes, have been considered as well.

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From Prochiral N-Heterocyclic Carbenes to Optically Pure Metal Complexes: New Opportunities in Asymmetric Catalysis

Cited by 48 publications

References 28 publications

Transition metal complexes bearing atropisomeric saturated NHC ligands

Transition metal complexes bearing atropisomeric saturated NHC ligands

C₁‐Symmetric Atropisomeric NHC Palladium(II) Complexes: Synthesis, Resolution and Characterization

Alternative Transformations of N-Heterocyclic Carbene Complexes of the Group 11 Metals in Transmetalation Reactions (A Review)

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From Prochiral N-Heterocyclic Carbenes to Optically Pure Metal Complexes: New Opportunities in Asymmetric Catalysis

Cited by 48 publications

References 28 publications

Transition metal complexes bearing atropisomeric saturated NHC ligands

Transition metal complexes bearing atropisomeric saturated NHC ligands

C1‐Symmetric Atropisomeric NHC Palladium(II) Complexes: Synthesis, Resolution and Characterization

Alternative Transformations of N-Heterocyclic Carbene Complexes of the Group 11 Metals in Transmetalation Reactions (A Review)

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C₁‐Symmetric Atropisomeric NHC Palladium(II) Complexes: Synthesis, Resolution and Characterization