Simple and Fast Synthesis of New Axially Chiral Bipyridine <i>N,N′</i>‐Dioxides for Highly Enantioselective Allylation of Aldehydes

Kadlčíková, Aneta; Hrdina, Radim; Valterová, Irena; Kotora, Martin

doi:10.1002/adsc.200900224

Cited by 69 publications

(39 citation statements)

References 49 publications

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“…promote the formation of hexacoordinate neutral silicon species 29. These observations and results thus provided the necessary background to understand the high level of asymmetric induction observed for allylations carried out in THF 27a,28…”

Section: Introductionmentioning

confidence: 66%

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Two‐Dimensional Electronic Conjugation: Statics and Dynamics at Structural Domains Beyond Molecular Wires

Opsitnick

Lee

2007

Chemistry A European J

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Chemical architectures supporting a high degree of electronic conjugation serve as important functional components in devices and materials for advanced electronic and photonic applications. Increasing the spatial dimensionality of such constructs can fundamentally modify their optoelectronic properties and significantly alter intra- and intermolecular interactions that are crucial for understanding and controlling charge/energy-transfer processes. In this article, emerging design principles in the construction of well-defined conjugated platforms beyond molecular wires are highlighted. Both covalent and noncovalent approaches can be strategically employed to position one-dimensional (1D) substructures in a spatially well-defined manner in order to enhance both structural and functional complexity in a two-dimensional (2D) setting. A predictable and controllable switching mechanism can be designed and implemented with mobile 2D electronic conjugation that operates by correlated motions of inherently rigid 1D subunits. This emerging "dynamic" approach complements and challenges the prevailing "static" paradigm of conjugated chemical architectures.

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Section: Introductionmentioning

confidence: 66%

“…Furthermore, we showed that the appropriate choice of the reaction medium,26,27a,28 that is, the solvent, was crucial for the course of the reaction and for asymmetric induction. In summary, although both reaction mechanisms proceed through six‐membered transition states, electrophilic solvents (CH 2 Cl 2 , MeCN, etc.)…”

Section: Introductionmentioning

confidence: 99%

Two‐Dimensional Electronic Conjugation: Statics and Dynamics at Structural Domains Beyond Molecular Wires

Opsitnick

Lee

2007

Chemistry A European J

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“…Once again, cross-cyclotrimerization catalyzed by CpCo(CO) 2 under microwave irradiation proved to be the convenient method of choice. Thus, the reaction of 10 with excess of benzonitrile and (R)-tetrahydrofurannitrile yielded the desired unsymmetrically substituted bis(tetrahydroisoquinolines) 21 and symmetrically substituted 11a in 28 and 20 % isolated yields, respectively [11]. The third possible product, 11f, was not detected.…”

Section: Synthesis Of Unsymmetrical Bis(tetrahydroisoquinolines)mentioning

confidence: 97%

Synthesis of axially chiral bipyridine N,N'-dioxides and enantioselective allylation of aldehydes

Kotora

2010

Pure and Applied Chemistry

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N-oxides possessing the pyridine framework are strong Lewis bases that can activate the C-Si bond of allylhalosilanes to such an extent that they catalyze reactions with aldehydes. N-oxides embedded in chiral scaffolds are usually capable of highly selective chirality transfer to the derived products. Our goal was to develop a general synthetic method allowing the preparation of structurally varied N,N'-dioxides suitable for enantioselective organocatalysis. The underlying synthetic strategy was based on [2 + 2 + 2]-cyclotrimerization of suitably substituted diynes with nitriles catalyzed by Co-complexes to generate the desired bipyridines, their further oxidation and resolution of which furnished the corresponding chiral N,N'-dioxides. The prepared compounds were used in catalytic allylation of aromatic aldehydes to homoallyl alcohols with high enantioselectivity (up to 96 % ee). Enantioselectivity, enantiodiscrimination, and the reaction mechanism are controlled by the choice of solvent.

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“…Initially, compounds were based on 4,4'-biquinoline and 2,2'-bipyridine N,N′-dioxide backbones (1 and 2, see Figure 1) which, apart from Nakajima's work, were also investigated by Feng and coworkers [28]. A little later, Kotora et al synthesized N-oxides with tetrahydroisoquinoline [29] and bis(tetrahydroisoquinoline) frameworks [30,31]. It is worth to highlight that organocatalysts 1 and 2 give, so far, one of the highest results (both in terms of yield and enantioselectivity) in the allylation of benzaldehyde with allyltrichlorosilane (85%, 88% ee (R) and 95%, 84% ee (S) respectively).…”

Section: Axially Chiral N-oxides and Nn′-dioxidesmentioning

confidence: 99%

“…Asymmetric allylation of aldehydes by 32 [50] and 34a [31]. The unsymmetrically substituted bis(tetrahydroisoquinoline) N,N'-dioxides 34a were also synthesized and employed in catalytic allylation of aromatic aldehydes (see Table 4) [31]. Again, the huge influence of the solvent on the stereochemical result of the reaction was observed.…”

Section: N-oxides With Central and Axial Chiralitymentioning

confidence: 99%

Heteroaromatic N-Oxides in Asymmetric Catalysis: A Review

Wrzeszcz

Siedlecka

2020

Molecules

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An increasing interest in the synthesis and use of optically active pyridine N-oxides as chiral controllers for asymmetric reactions has been observed in the last few years. Chiral heteroaromatic N-oxides can work as powerful electron-pair donors, providing suitable electronic environments in the transition state formed within the reaction. The nucleophilicity of the oxygen atom in N-oxides, coupled with a high affinity of silicon to oxygen, represent ideal properties for the development of synthetic methodology based on nucleophilic activation of organosilicon reagents. The application of chiral N-oxides as efficient organocatalysts in allylation, propargylation, allenylation, and ring-opening of meso-epoxides, as well as chiral ligands for metal complexes catalyzing Michael addition or nitroaldol reaction, can also be found in the literature. This review deals with stereoselective applications of N-oxides, and how the differentiating properties are correlated with their structure. It contains more recent results, covering approximately the last ten years. All the reported examples have been divided into five classes, according to the chirality elements present in their basic molecular frameworks.

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Simple and Fast Synthesis of New Axially Chiral Bipyridine N,N′‐Dioxides for Highly Enantioselective Allylation of Aldehydes

Cited by 69 publications

References 49 publications

Two‐Dimensional Electronic Conjugation: Statics and Dynamics at Structural Domains Beyond Molecular Wires

Two‐Dimensional Electronic Conjugation: Statics and Dynamics at Structural Domains Beyond Molecular Wires

Synthesis of axially chiral bipyridine N,N'-dioxides and enantioselective allylation of aldehydes

Heteroaromatic N-Oxides in Asymmetric Catalysis: A Review

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