Phase Transfer of Enantiopure Werner Cations into Organic Solvents: An Overlooked Family of Chiral Hydrogen Bond Donors for Enantioselective Catalysis

Ganzmann, Carola; Gladysz, J. A.

doi:10.1002/chem.200800226

Cited by 83 publications

(96 citation statements)

References 44 publications

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“…The use of chiral metal complexes as chiral “metalloligands” was first demonstrated by Gladysz et al . With respect to octahedral coordination complexes, Ganzmann and Gladysz reported in 2008 that the cobalt complex Δ‐[Co(1,2‐ethylenediamine) 3 ] 3+ ( 5 ), in combination with the large counterion tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate (BArF) catalyzed the Michael addition of dimethyl malonate to 2‐cyclopentene‐1‐one with 33 % ee (Figure c) . Despite weak asymmetric induction, the simplicity of the inert octahedral template is appealing because it contains three identical ligands assembled around a stereogenic octahedral cobalt center.…”

Section: Early Studiesmentioning

confidence: 99%

Stereogenic‐Only‐at‐Metal Asymmetric Catalysts

Zhang

Meggers

2017

Chemistry An Asian Journal

110

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Chirality is an essential feature of asymmetric catalysts. This review summarizes asymmetric catalysts that derive their chirality exclusively from stereogenic metal centers. Reported chiral-at-metal catalysts can be divided into two classes, namely, inert metal complexes, in which the metal fulfills a purely structural role, so catalysis is mediated entirely through the ligand sphere, and reactive metal complexes. The latter are particularly appealing because structural simplicity (only achiral ligands) is combined with the prospect of particularly effective asymmetric induction (direct contact of the substrate with the chiral metal center). Challenges and solutions for the design of such reactive stereogenic-only-at-metal asymmetric catalysts are discussed.

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Section: Early Studiesmentioning

confidence: 99%

Stereogenic‐Only‐at‐Metal Asymmetric Catalysts

Zhang

Meggers

2017

Chemistry An Asian Journal

110

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“…Recently, we introduced a new class of stereochemically inert coordinatively saturated chiral complexes of cobalt(III) as promoters of asymmetric carbon–carbon bond forming reactions . The use of chiral octahedral complexes, where the metal ion is not involved in the catalytic act and only serves to position and activate organic groups of a ligand, is a fast evolving new field of research . An efficient group of such catalysts developed by our group are cationic complexes of cobalt(III) and Schiff bases obtained from substituted salicylic aldehydes and ( R,R )‐ or ( S,S )‐cyclohexane diamine (Figure ) .…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5][6] The use of chiral octahedral complexes, where the metal ion is not involved in the catalytic act and only serves to positiona nd activate organic groups of al igand,i safast evolvingn ew field of research. [7][8][9][10][11][12][13][14][15] An efficient group of such catalysts developed by our group are cationic complexes of cobalt(III) and Schiff bases obtained from substituted salicylic aldehydes and (R,R)-or (S,S)-cyclohexane diamine (Figure 1). [5,6] The NÀHb onds of the coordinated ligandsw ere activated by the Lewis acidity of the central metal ion, becoming better Brønsteda cids (so called Lewis-acid activated Brønsted catalysis [16] ).…”

Section: Introductionmentioning

confidence: 99%

Chiral Cobalt(III) Complexes as Bifunctional Brønsted Acid–Lewis Base Catalysts for the Preparation of Cyclic Organic Carbonates

et al. 2015

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Stereochemically inert cationic cobalt(III) complexes were shown to be one-component catalysts for the synthesis of cyclic carbonates from epoxides and carbon dioxide at 50 °C and 5 MPa carbon dioxide pressure. The optimal catalyst possessed an iodide counter anion and could be recycled. A catalytic cycle is proposed in which the ligand of the cobalt complexes acts as a hydrogen-bond donor, activating the epoxide towards ring opening by the halide anion and activating the carbon dioxide for subsequent reaction with the halo-alkoxide. No kinetic resolution was observed when terminal epoxides were used as substrates, but chalcone oxide underwent kinetic resolution.

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Chiral‐at‐Metal Octahedral Iridium Catalyst for the Asymmetric Construction of an All‐Carbon Quaternary Stereocenter

et al. 2013

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Asymmetric catalysts, whether metal complexes with chiral ligands, chiral organometallics, or chiral organic compounds (organocatalysts), achieve asymmetric induction by transferring chiral information from the catalyst to the substrate(s). [1] The source of the catalysts chirality therefore plays a crucial role for its mode of action, and is typically derived from one or more tetrahedral stereogenic centers (mostly carbon atoms, but also heteroatoms, such as sulfur or phosphorus), axial chirality, planar chirality, or a combination thereof (Scheme 1). In contrast, only few reports exist of asymmetric catalysts that derive their chirality exclusively from an octahedral stereocenter. [2][3][4] This seems surprising, considering the prevalence of the octahedral coordination geometry in chemistry and its ability to support the generation of structures with high complexity and, as a result of ligand crowding and chelate effects, often low conformational flexibility. [5] We recently demonstrated the use of chiral-atmetal octahedral complexes for the tailored design of a highly efficient asymmetric noncovalent catalyst that requires low catalyst loading by reporting an inert iridium(III)-based catalyst for the conjugate asymmetric transfer hydrogenation of b,b-disubstituted nitroalkenes. [6] However, excellent metal-, bio-, and organo-catalysts already exist for this transformation, [7] and we were therefore wondering whether an octahedral chiral-at-metal catalyst could be developed for a more challenging asymmetric conversion. In this respect, the asymmetric conjugate addition of carbon nucleophiles to b,b-disubstituted nitroalkenes constitutes a highly attractive reaction as it permits the construction of a stereogenic carbon atom bound to four other carbon substituents (all-carbon quaternary stereocenter). [8] Only a handful of studies are available dealing with this particular reaction, thereby presumably reflecting the involved challenge of overcoming a significant steric repulsion between the incoming carbon nucleophile and the carbon substituents of the nitroalkene electrophile. Nevertheless, Hoveyda and co-workers introduced a Cu-catalyzed dialkylzinc conjugate addition, [9] Arai and co-workers reported a Cu-catalyzed addition of indoles to isatin-derived nitroalkenes, [10] Jia and co-workers disclosed a Ni-catalyzed addition of indoles to b-CF 3 -b-disubstituted nitroalkenes, [11] Ricci and co-workers reported a phase-transfer asymmetric organocatalytic conjugate addition of cyanide to b,b-disubstituted nitroalkenes, albeit with only modest enantioselectivities, [12] Melchiorre and co-workers introduced the asymmetric vinylogous Michael addition of cyclic enones to nitroalkenes catalyzed by natural cinchona alkaloids, including one reaction using a b,b-disubstituted nitroalkene, [13] and finally Kastl and Wennemers introduced a proline-peptide-catalyzed asymmetric addition of aldehydes to b,b-disubstituted nitroalkenes under formation of g-nitroaldehydes. [14] The restricted scope of dialkylzinc reagents and t...

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Phase Transfer of Enantiopure Werner Cations into Organic Solvents: An Overlooked Family of Chiral Hydrogen Bond Donors for Enantioselective Catalysis

Cited by 83 publications

References 44 publications

Stereogenic‐Only‐at‐Metal Asymmetric Catalysts

Stereogenic‐Only‐at‐Metal Asymmetric Catalysts

Chiral Cobalt(III) Complexes as Bifunctional Brønsted Acid–Lewis Base Catalysts for the Preparation of Cyclic Organic Carbonates

Chiral‐at‐Metal Octahedral Iridium Catalyst for the Asymmetric Construction of an All‐Carbon Quaternary Stereocenter

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