Intermolecular, redox-neutral azidoarylation of alkenes<i>via</i>photoredox catalysis

Chen, Jian; Zhu, Shuaishuai; Qin, Jian; Chu, Lingling

doi:10.1039/c9cc00241c

Cited by 63 publications

(45 citation statements)

References 61 publications

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“…Benzyl radicals, generated by oxidation and α‐fragmentation of 1‐benzyl‐tetrahydroisoquinolines, were successfully arylated with radical anions of type 68 (Figure f), and arylation of benzyl and allyl radicals was realized by using benzyl‐ or vinylpinacolboranes as substrates (Figure g) . Recently, an intermolecular α‐azido‐β‐arylation of alkenes with cyanopyridines and TMSN 3 as reagents has been reported based on the same strategy . In this cascade, the azidyl radical is oxidatively generated along with the radical anion 68 by using a redox catalyst.…”

Section: Metal‐free Processesmentioning

confidence: 99%

“…[91] Recently,a ni ntermolecular a-azido-b-arylation of alkenes with cyanopyridines and TMSN 3 as reagents has been reported based on the same strategy. [92] In this cascade,t he azidyl radical is oxidatively generated along with the radical anion 68 by using ar edox catalyst. Thea zidyl radical adds terminally to the alkene,a nd subsequent trapping of the adduct radical with 68 provides,after cyanide fragmentation, the b-arylated alkyl azides (Figure 19 h).…”

Section: Cyanoarenesmentioning

confidence: 99%

“…Radical-radical cross-couplingreaction with cyanoarenes 66 using photoredox catalysis. [85][86][87][88][89][90][91][92][93] desired cross-coupling product can be achieved if an excess of the precursor of the radical showing the longer-lifetime-the cyanoarene (10 equiv [98a] and 5equiv [98b] )-is used.…”

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: Metal‐free Processesmentioning

confidence: 99%

Section: Cyanoarenesmentioning

confidence: 99%

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The Persistent Radical Effect in Organic Synthesis

2019

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“…Die Arylierung von Benzyl‐ und Allyl‐Radikalen konnte auch durch den Einsatz von Benzyl‐ oder Vinylpinakolboranen realisiert werden (Abbildung g) . Kürzlich wurde dieselbe Strategie auch verwendet, um eine intermolekulare α‐Azido‐β‐arylierung von Alkanen mit Cyanopyridinen und TMSN 3 als Reagenzien durchzuführen . In dieser Kaskade wird das Azidyl‐Radikal oxidativ unter Verwendung eines Photoredoxkatalysators erzeugt und der Katalysator durch Erzeugung des Radikalanions 68 regeneriert.…”

Section: Metall‐freie Prozesseunclassified

“…[91] Kürzlich wurde dieselbe Strategie auch verwendet, um eine intermolekulare a-Azido-b-arylierung von Alkanen mit Cyanopyridinen und TMSN 3 als Reagenzien durchzuführen. [92] [95] kçnnen nur Wasserstoffe von aktivierten C-H-Bindungen abstrahiert werden. Dies führt zum einem zu einem selektiven HAT-Schritt, limitiert aber auf der anderen Seite die Anwendungsbreite der Reaktion.…”

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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Catalytic Azido‐Hydrazination of Alkenes Enabled by Visible Light: Mechanistic Studies and Synthetic Applications

et al. 2019

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A visible-light-enabled catalytic intermolecular azido-hydrazination method for unactivated alkenes is developed via an orderly radical addition sequence. This transformation features metal-free and redoxneutral conditions and is applicable to a wide range of alkenes with commercially available reagents. Mechanistic and kinetic studies reveal that the efficient generation of azide radical enabled by fluorenone under visible-light is critical to this methodology. The β-azido alkyl hydrazines prepared with this reaction can be conveniently derived to valuable synthetic building blocks, and one of the products has been successfully applied in the total synthesis of (�)-ibrutinib, which is used to treat B cell cancers.

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Intermolecular, redox-neutral azidoarylation of alkenesviaphotoredox catalysis

Abstract: An intermolecular, redox-neutral azidoarylation of alkenes with pyridines and TMSN3 has been reported via visible light-induced photoredox catalysis.

Cited by 63 publications

References 61 publications

The Persistent Radical Effect in Organic Synthesis

The Persistent Radical Effect in Organic Synthesis

Der “Persistent Radical Effect” in der organischen Chemie

Catalytic Azido‐Hydrazination of Alkenes Enabled by Visible Light: Mechanistic Studies and Synthetic Applications

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