Regio- and chemoselective Csp<sup>3</sup>–H arylation of benzylamines by single electron transfer/hydrogen atom transfer synergistic catalysis

Ide, Takafumi; Barham, Joshua P.; Fujita, Masashi; Kawato, Yuji; Egami, Hiromichi; Hamashima, Yoshitaka

doi:10.1039/c8sc02965b

Cited by 102 publications

(72 citation statements)

References 108 publications

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“…Considering the S−H bond energy of around 354 kJ mol −1 , the thiyl radical can only abstract a hydrogen atom from an activated C−H bond, rendering the HAT step selective but at the same time also limiting the substrate range. Hence, benzylic alcohols/ethers (Figure a), alkenes, alkylarenes (Figure b), and benzyl amines (Figure c) are suitable substrates. The C radical is then trapped by a radical anion 68 and ionic cyanide fragmentation affords the direct C−H arylation product 69 .…”

Section: Metal‐free Processesmentioning

confidence: 99%

“…Under basic conditions,t he thiol formed is deprotonated to the thiolate, which is then oxidized to the thiyl radical by the photoredox catalyst. Considering the SÀHb ond energy of around 354 kJ mol À1 , [95] the thiyl radical can only abstract ahydrogen atom from an activated C À Hb ond, rendering the HATs tep selective but at the same time also limiting the substrate range.H ence,b enzylic alcohols/ethers (Figure 20 a), [94] alkenes, [96] alkylarenes (Figure 20 b), [96c] and benzyl amines (Figure 20 c) [97] are suitable substrates.T he Cradical is then trapped by aradical anion 68 and ionic cyanide fragmentation affords the direct C À Harylation product 69.Along with thiols (R 2 SH), sulfonamides (R 2 ArSO 2 NH) were also implemented as cocatalysts to mediate the HATstep. [96c] In addition to the many examples dealing with redoxneutral processes,t here are also procedures in which both radical species are generated by reduction using as toichiometric reducing reagent.…”

Section: Cyanoarenesmentioning

confidence: 99%

“…Coupling of cyanoarenes with activated alkanes via HAT. [94,96,97] Figure 21. Pyridine-boryl radical as ap ersistent radical.…”

Section: Ketyls and A-amido Alkyl Radical Anionsmentioning

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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“…Dies führt zum einem zu einem selektiven HAT‐Schritt, limitiert aber auf der anderen Seite die Anwendungsbreite der Reaktion. Daher sind benzylische Alkohole/Ether (Abbildung a), Alkene, Alkylarene (Abbildung b) und benzylische Amine (Abbildung c) mögliche Substrate. Das C‐Radikal wird vom Radikalanion 68 abgefangen und die ionische Cyanid‐Fragmentierung liefert das Produkt 69 .…”

Section: Metall‐freie Prozesseunclassified

“…Dies führt zum einem zu einem selektiven HAT-Schritt, limitiert aber auf der anderen Seite die Anwendungsbreite der Reaktion. Daher sind benzylische Alkohole/Ether (Abbildung 20 a), [94] Alkene, [96] Alkylarene (Abbildung 20 b) [96c] und benzylische Amine (Abbildung 20 c) [97] mçgliche Substrate.D as C-Radikal wird vom Radikalanion 68 abgefangen und die ionische Cyanid-Fragmentierung liefert das Produkt 69.N eben Thiolen (R 2 SH) wurden auch Sulfonamide (R 2 ArSO 2 NH) als Cokatalysatoren fürden HAT-Schritt eingesetzt. [96c] Neben den vielen Beispielen eines Redox-neutralen Prozesses gibt es auch Reaktionen, in denen beide Radikalspezies über eine Reduktion durch den Einsatz eines stçchiometrischen Reagenzes gebildet werden.…”

Section: Cyanoareneunclassified

Der “Persistent Radical Effect” in der organischen Chemie

Leifert

Studer

2019

Angewandte Chemie

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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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CH Arylation of Saturated N ‐Heterocycles

Haldar

Mandal

Jana

2022

Handbook of CH-Functionalization

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Saturated N ‐heterocycles having an aryl group are core structures of numerous natural products, pharmaceuticals, chiral catalysts, etc. Therefore, different strategies have been developed for the synthesis of arylated N ‐heterocycles. In contrast to multistep synthesis, the development of direct arylation of saturated N ‐heterocycles has become increasingly popular in recent years. This article summarizes the methods for the synthesis of arylated N ‐heterocycles through direct CH arylation of alicyclic amines.

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Regio- and chemoselective Csp³–H arylation of benzylamines by single electron transfer/hydrogen atom transfer synergistic catalysis

Abstract: Catalyst controlled regio-, and chemo-selective C-H arylation of benzylamines.

Cited by 102 publications

References 108 publications

The Persistent Radical Effect in Organic Synthesis

The Persistent Radical Effect in Organic Synthesis

Der “Persistent Radical Effect” in der organischen Chemie

CH Arylation of Saturated N ‐Heterocycles

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Regio- and chemoselective Csp3–H arylation of benzylamines by single electron transfer/hydrogen atom transfer synergistic catalysis

Abstract: Catalyst controlled regio-, and chemo-selective C-H arylation of benzylamines.

Cited by 102 publications

References 108 publications

The Persistent Radical Effect in Organic Synthesis

The Persistent Radical Effect in Organic Synthesis

Der “Persistent Radical Effect” in der organischen Chemie

CH Arylation of Saturated N ‐Heterocycles

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Product

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Regio- and chemoselective Csp³–H arylation of benzylamines by single electron transfer/hydrogen atom transfer synergistic catalysis