Alkyl Carbon–Carbon Bond Formation by Nickel/Photoredox Cross‐Coupling

Milligan, John A.; Phelan, James P.; Badir, Shorouk O.; Molander, Gary A.

doi:10.1002/anie.201809431

Cited by 525 publications

(316 citation statements)

References 147 publications

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“…The groups of Molander, MacMillan, and Baran introduced Ni‐catalyzed cross‐coupling by radical decarboxylation or deboronation. Molander and MacMillan used alkyl trifluoroborates, carboxylates, or later also N‐alkylated 1,4‐dihydropyridines (DHP) and silicates as the C radical precursors, which, after SET oxidation by a photoredox catalyst, fragment to the corresponding alkyl radicals R . (Figure a).…”

Section: Radical–metal Crossover Reactionsmentioning

confidence: 99%

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: Radical–metal Crossover Reactionsmentioning

confidence: 99%

The Persistent Radical Effect in Organic Synthesis

2019

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“…Die Gruppen von Molander, MacMillan und Baran führten Ni‐katalysierte Kreuzkupplungen mittels radikalischer Decarboxylierung oder Deborierung ein. Molander und MacMillan verwendeten Alkyltrifluorborate, Carboxylate oder später auch N‐alkylierte 1,4‐Dihydropyridine (DHP) und Silicate als C‐Radikalvorläufer, welche nach SET‐Oxidation durch einen Photoredoxkatalysator zu den entsprechenden Alkyl‐Radikalen R . fragmentieren (Abbildung a).…”

Section: Radikal‐metall‐kreuzungsreaktionenunclassified

“… Decarboxylierende/deborylierende Nickel‐katalysierte Kreuzkupplung mittels a) oxidativem Ansatz ausgehend von Carboxylaten, Boraten, Dihydropyridinen und Alkylsilicaten (cat=Brenzcatechin) oder b) reduktivem Ansatz ausgehend von Aktivestern …”

Section: Radikal‐metall‐kreuzungsreaktionenunclassified

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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“…Our recent discovery of an ickel catalyzed carboiodination [5a] and the potential for an alternative mechanism [6] opened the door to exploring the creation of highly sensitive benzylic iodides.T ot he best of our knowledge,t here is only one example of nickel catalyzed dearomative functionalization, [7] leaving this concept largely unexplored. Nickel is known to catalyze the reductive elimination of aC (sp 2 ) À X bond [8] however,t he formation of aC (sp 3 ) À Xb ond is rare.…”

mentioning

confidence: 99%

Forming Benzylic Iodides via a Nickel Catalyzed Diastereoselective Dearomative Carboiodination Reaction of Indoles

et al. 2019

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Ad iastereoselective dearomative carboiodination reaction is reported. We report an ovel metal-catalyzed approach to install reactive secondary benzylic iodides. Utilizing the unique reactivity of nickel, we have expanded the carboiodination reaction to non-activated aromatic double bonds forming ap reviously unattainable class of iodides.W e also report ab roadly applicable method to avoid the use of ametallic reducing agent by utilizing an alkylphosphite as the ligand. The reaction is thought to proceed through as yn intramolecular carbonickelation across a2 -substituted indole followed by ad iastereoretentive reductive elimination of the carbonÀiodine bond. The complex iodinated indolines generated in the reaction were obtained in moderate to good yields and good to excellent diastereoselectivity.T he products were easily functionalized by av ariety of synthetic methods.

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Alkyl Carbon–Carbon Bond Formation by Nickel/Photoredox Cross‐Coupling

Cited by 525 publications

References 147 publications

The Persistent Radical Effect in Organic Synthesis

The Persistent Radical Effect in Organic Synthesis

Der “Persistent Radical Effect” in der organischen Chemie

Forming Benzylic Iodides via a Nickel Catalyzed Diastereoselective Dearomative Carboiodination Reaction of Indoles

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