Perfluoroalkylative pyridylation of alkenes<i>via</i>4-cyanopyridine-boryl radicals

Cao, Jun; Wang, Guoqiang; Gao, Liuzhou; Chen, Hui; Liu, Xueting; Xu, Cheng; Li, Shuhua

doi:10.1039/c8sc05237a

Cited by 88 publications

(40 citation statements)

References 105 publications

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“…Reductive arylation of ketones with 64 is achieved with pinacoldiborane (B 2 pin 2 )asareagent. Theaddition of B 2 pin 2 to cyanopyridine 64 leads to the formation of the neutral borylated cyanopyridine radical 70 ( Figure 21), [99] which is assumed to be ap ersistent species.I nt he presence of a,bunsaturated ketones or ketones,reductive g-ora-pyridylation occurs to provide products 71 and 73 after hydrolysis.B ased on DFT calculations and radical clock experiments,t he authors claimed that the transient intermediates 72 and 74 are generated as coupling partners of the persistent radical 70.…”

Section: Cyanoarenesmentioning

confidence: 99%

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The Persistent Radical Effect in Organic Synthesis

2019

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Radical–radical couplings are mostly nearly diffusion‐controlled processes. Therefore, the selective cross‐coupling of two different radicals is challenging and not a synthetically valuable transformation. However, if the radicals have different lifetimes and if they are generated at equal rates, cross‐coupling will become the dominant process. This high cross‐selectivity is based on a kinetic phenomenon called the persistent radical effect (PRE). In this Review, an explanation of the PRE supported by simulations of simple model systems is provided. Radical stabilities are discussed within the context of their lifetimes, and various examples of PRE‐mediated radical–radical couplings in synthesis are summarized. It is shown that the PRE is not restricted to the coupling of a persistent with a transient radical. If one coupling partner is longer‐lived than the other transient radical, the PRE operates and high cross‐selectivity is achieved. This important point expands the scope of PRE‐mediated radical chemistry. The Review is divided into two parts, namely 1) the coupling of persistent or longer‐lived organic radicals and 2) “radical–metal crossover reactions”; here, metal‐centered radical species and more generally longer‐lived transition‐metal complexes that are able to react with radicals are discussed—a field that has flourished recently.

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Section: Cyanoarenesmentioning

confidence: 99%

“…Pyridine-boryl radical as ap ersistent radical. [99] Figure 22. Cross-coupling of benzylic ethers with imines via a-amido alkyl radical anions.…”

Section: Ketyls and A-amido Alkyl Radical Anionsmentioning

confidence: 99%

The Persistent Radical Effect in Organic Synthesis

2019

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“…In 2019, Li and co-workers developed a perfluoroalkylative pyridylation reaction of alkenes (Scheme 38). 59 The pyridine-boryl radical 75, generated by the reaction of 4-cyanopyridine with B 2 pin 2 , underwent halogen-atom abstraction with the C-I or C-Br bond in a haloperfluoroalkane to afford a perfluoroalkyl radical (R f •), which then added to the alkene substrate to produce radical adduct 78. Subsequently, radical-radical coupling between 78 and the pyridine-boryl radical 75, followed by elimination of the pinBCN, generated the 4-functionalized pyridines 79.…”

Section: Cluster Synlettmentioning

confidence: 99%

Recent Developments in Transition-Metal-Free Functionalization and Derivatization Reactions of Pyridines

Zhou

Jiao²

2020

Synlett

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Pyridine is an important structural motif that is prevalent in natural products, drugs, and materials. Methods that functionalize and derivatize pyridines have gained significant attention. Recently, a large number of transition-metal-free reactions have been developed. In this review, we provide a brief summary of recent advances in transition-metal-free functionalization and derivatization reactions of pyridines, categorized according to their reaction modes.1 Introduction2 Metalated Pyridines as Nucleophiles2.1 Deprotonation2.2 Halogen–Metal exchange3 Activated Pyridines as Electrophiles3.1 Asymmetric 2-Allylation by Chiral Phosphite Catalysis3.2 Activation of Pyridines by a Bifunctional Activating Group3.3 Alkylation of Pyridines by 1,2-Migration3.4 Alkylation of Pyridines by [3+2] Addition3.5 Pyridine Derivatization by Catalytic In Situ Activation Strategies3.6 Reactions via Heterocyclic Phosphonium Salts4 Radical Reactions for Pyridine Functionalization4.1 Pyridine Functionalization through Radical Addition Reactions4.2 Pyridine Functionalization through Radical–Radical Coupling Reactions5 Derivatization of Pyridines through the Formation of Meisenheimer-Type Pyridyl Anions6 Conclusion

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“…Pyridin-Boryl-Radikal als persistentes Radikal. [99] Abbildung 22. Kreuzkupplung eines benzylischen Ethers mit Iminen über a-Amidoalkyl-Radikalanionen.…”

Section: Cyanoareneunclassified

Der “Persistent Radical Effect” in der organischen Chemie

2019

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Radikal‐Radikal‐Kupplungen sind nahezu diffusionskontrollierte Prozesse. Daher sind selektive Kreuzkupplungen zweier unterschiedlicher Radikale schwierig zu realisieren und stellen somit synthetisch nicht wertvolle Prozesse dar. Wenn die beiden Radikale allerdings eine unterschiedliche Lebensdauer aufweisen und in gleichen Raten gebildet werden, wird die Kreuzkupplung zum dominierenden Prozess. Die hohe Kreuzselektivität basiert auf einem kinetischen Phänomen, dem “Persistent Radical Effect” (PRE). In diesem Aufsatz wird eine von Simulationen einfacher Modellsysteme gestützte Erklärung des PRE geliefert. Weiter werden die Stabilität von Radikalen in Bezug auf ihre Lebensdauer und verschiedene Beispiele für PRE‐vermittelte Radikal‐Radikal‐Kupplungen in der Synthese diskutiert. Es wird gezeigt, dass der PRE nicht auf Kupplungen persistenter mit transienten Radikalen beschränkt ist. Der PRE mit einhergehender hoher Kreuzselektivität greift bereits, wenn ein Kupplungspartner langlebiger als das andere transiente Radikal ist. Diese Tatsache erweitert signifikant das Anwendungsgebiet PRE‐vermittelter Radikalchemie. Dieser Aufsatz ist in zwei Teile aufgeteilt: 1) die Kupplung persistenter oder langlebiger organischer Radikale und 2) Radikal‐Metall‐Kreuzungsreaktionen; hierbei werden Metall‐zentrierte Radikalspezies oder allgemeiner langlebige Übergangsmetallkomplexe, welche mit Radikalen reagieren, diskutiert – ein Gebiet, das jüngst stark expandiert ist.

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Perfluoroalkylative pyridylation of alkenesvia4-cyanopyridine-boryl radicals

Abstract: A metal- and photo-free method for the perfluoroalkylative pyridylation of alkenes has been developed.

Cited by 88 publications

References 105 publications

The Persistent Radical Effect in Organic Synthesis

The Persistent Radical Effect in Organic Synthesis

Recent Developments in Transition-Metal-Free Functionalization and Derivatization Reactions of Pyridines

Der “Persistent Radical Effect” in der organischen Chemie

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