Quaternary Centers by Nickel‐Catalyzed Cross‐Coupling of Tertiary Carboxylic Acids and (Hetero)Aryl Zinc Reagents

Chen, Tie Gen; Zhang, Haolin; Mykhailiuk, Pavel K.; Merchant, Rohan R.; Smith, Christopher J.; Qin, Tian; Baran, Phil S.

doi:10.1002/anie.201814524

Cited by 89 publications

(59 citation statements)

References 48 publications

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“… Decarboxylative/deborylative nickel‐catalyzed cross‐coupling using a) an oxidative approach starting with carboxylates, boronates, dihydropyridines, and alkyl silicates (cat=catechol) or b) a reductive approach starting with active esters …”

Section: Radical–metal Crossover Reactionsmentioning

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: Radical–metal Crossover Reactionsmentioning

confidence: 99%

“…Reductive elimination leads to the cross‐coupling product Ar‐R and a Ni I complex. The resulting Ni I complex then undergoes transmetalation with aryl boronic acids, aryl, vinyl, and alkyl zinc compounds to provide the redox‐active arylNi(I) complex closing the catalytic cycle.…”

Section: Radical–metal Crossover Reactionsmentioning

confidence: 99%

The Persistent Radical Effect in Organic Synthesis

2019

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“…Interestingly, the reaction of redox‐active ester 2 bd obtained from gabapentin, provided an unusual product which was thought to be generated by a 1,5‐hydrogen atom transfer (1,5‐HAT) prior to nickel mediated cross‐coupling (Figure a). As noted by others, the limitation of this procedure was the lack of reactivity towards tertiary redox‐active esters . Adamantane carboxylic acid and tert ‐butyl carboxylic acid phthalimide ester both failed to deliver desired product under our standard conditions.…”

Section: Figurementioning

confidence: 72%

A Practical Method for Continuous Production of sp3‐Rich Compounds from (Hetero)Aryl Halides and Redox‐Active Esters

Watanabe¹,

Chen

May

et al. 2019

Chemistry A European J

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A practically useful coupling reaction between aromatic halides and redox‐active esters was realized by nickel catalysis through the use of a packed zinc bed column in continuous flow. Multiple reuse of the column showed a negligible decrease in efficiency, affording high space/time yields. A wide range of substrates, including a number of heteroaryl halides and polyfunctional materials were coupled in generally good yields. Longer‐time and larger‐scale experiments further demonstrates the robustness of the system.

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“… 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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Quaternary Centers by Nickel‐Catalyzed Cross‐Coupling of Tertiary Carboxylic Acids and (Hetero)Aryl Zinc Reagents

Cited by 89 publications

References 48 publications

The Persistent Radical Effect in Organic Synthesis

The Persistent Radical Effect in Organic Synthesis

A Practical Method for Continuous Production of sp3‐Rich Compounds from (Hetero)Aryl Halides and Redox‐Active Esters

Der “Persistent Radical Effect” in der organischen Chemie

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