Negishi Cross‐Couplings Compatible with Unprotected Amide Functions

Manolikakes, Georg; Dong, Mengshu; Mayr, Herbert; Li, Jinshan; Knöchel, Paul

doi:10.1002/chem.200802349

Cited by 71 publications

(38 citation statements)

References 32 publications

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“…Metal-halogen exchange reactions constitute one of the most powerful synthetic tools to functionalise aromatic molecules (35). Zn-halogen exchange reactions of aromatic halides are particularly important because they allow the preparation of arylzinc compounds that are key precursors in Negishi cross-coupling processes (36)(37)(38). Whereas more polar (and therefore more reactive) organometallics such as organolithium or organomagnesuium reagents are well established metal-halogen exchange reagents, less polar dialkylzinc compounds are more reluctant to react with aryl iodides and the presence of additives or catalytic conditions is required for the Zn-I exchange reaction to occur at a reasonable rate.…”

Section: Resultsmentioning

confidence: 99%

“…Because Mg-Zn hybrid 5 possesses three covalent Zn-C (aryl) bonds within an anionic-activated "ate" structure, it could potentially be an excellent precursor in Negishi cross-coupling reactions (36)(37)(38). Therefore, to evaluate the synthetic utility of 5, we carried out test reactions of solutions of 5 (prepared in situ) with 3 M equivalents of iodobenzene in the presence of 2.5 mol% ½PdCl 2 ðdppfÞ [dppf ¼ 1; 1 0 -bis(diphenylphosphino)ferrocene] (Scheme 4).…”

Section: Resultsmentioning

confidence: 99%

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Exposing the hidden complexity of stoichiometric and catalytic metathesis reactions by elucidation of Mg-Zn hybrids

Hevia

Chua

García‐Álvarez

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

100

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Studying seemingly simple metathesis reactions between ZnCl 2 and t BuMgCl has, surprisingly, revealed a much more complex chemistry involving mixed magnesium-zinc compounds that could be regarded as Mg-Zn hybrids. Thus, the reaction of equimolar amounts of ZnCl 2 and t BuMgCl reveals the formation of the unprecedented mixed Mg-Zn complex [ðTHFÞ 4 Mgðμ-ClÞ 2 Znð t BuÞðClÞ] (1), as a result of the co-complexation of the two anticipated exchange products of the metathesis. This magnesium zincate adopts a contacted ion-pair structure, closely related to Knochel's pioneering "Turbo" Grignard reagents. Furthermore, a second coproduct identified in this reaction is the solvent-separated mixed magnesiumzinc chloride complex [fMgðTHFÞ 6 g 2þ fZn 2 Cl 6 g 2− ] (3) that critically diminishes the amount of ZnCl 2 available for the intended metathesis reaction to take place. In another surprising result, when the reaction is carried out by using an excess of 3 M equivalents of the Grignard reagent (closer to the catalytic conditions employed by synthetic chemists), solvent-separated magnesium trialkyl zincate [fMg 2 Cl 3 ðTHFÞ 6 g þ fZnð t BuÞ 3 g − ] (4) is obtained that can be viewed as a model for the active species involved in the increasingly important organic transformations of Grignard reagents catalysed by ZnCl 2 . Furthermore, preliminary reactivity studies reveal that complex 4 can be used as an effective new reagent for direct Zn-I exchange reactions that allow the preparation and structural identification of the magnesium tris(aryl) zincate [fMg 2 Cl 3 ðTHFÞ 6 g þ fZnðp-TolÞ 3 g − ] (5) that represents the first example of complete 3-fold activation of a zincate in a Zn-I exchange reaction which, in turn, can efficiently be used as a precursor for Negishi crosscoupling reactions.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Exposing the hidden complexity of stoichiometric and catalytic metathesis reactions by elucidation of Mg-Zn hybrids

Hevia

Chua

García‐Álvarez

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

100

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“…Até então, na literatura existiam relatos apenas da aplicação de ésteres e de ácidos borônicos como substratos capazes de reagir com substratos amídicos sem a necessidade proteção prévia. 54 Os autores demonstraram que a utilização de um sistema catalítico composto por Pd(AcO) 2 a 1 mol% e o ligante 1-diciclohexilfosfino-2',6'-dimetoxibifenila (SPhos) a 2 mol% em contato com brometos de arila, por 90 minutos antes da adição do organozinco, permitia que o acoplamento de Negishi ocorresse em bons rendimentos para uma grande quantidade de eletrófilos contendo o grupo amida e sulfonamida, sem que outras bases fossem adicionadas para desprotonação das mesmas e sem necessidade de aplicação de um grande excesso do nucleófilo (Tabela 8). o C e 20 o C, respectivamente, fornece os produtos de hidrogenação total 2,3-dialquílicos.…”

Section: Uso De Micro-ondasunclassified

C-C Cross-Coupling: New Methodologies, Applications and Discoveries over the Last Few Years

Batalha¹,

Sagrillo²,

Gama³

2014

Revista Virtual De Química

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Abstract:The possibility of obtaining new C-C bonds from the transition metals mediated catalysis, has represented a major advance in Organic Synthesis and correlated areas such as Chemistry of Natural Products and Medicinal Chemistry, since synthetically unreachable molecules could be obtained in an efficient and chemosselective way, from simple reactants. The cross-coupling reactions, as some of these processes are called, have gained prominence since the original publications of Suzuki-Miyaura, Kumada-Tamao-Corriu, Mizoroki-Heck, Sonogashira, Stille -during the 1970's -and Hiyama -in 1988. Since then numerous efforts are made by scientists around the world in order to not only understand better these processes, but also develop new catalytic systems with more efficiency and applicable to a wider range of substrates and the concepts of Green Chemistry. This work aims to expose some of the advances published by scientists around the world, in the last six years, based on this theme.Keywords: Cross coupling; new substrates; microwaves; palladium; gold. ResumoA possibilidade de se obter novas ligações C-C, a partir de reações de catálise mediadas por metais de transição, tem representado um grande avanço em Síntese Orgânica e áreas correlatas como a Química de Produtos Naturais e a Química Medicinal, uma vez que moléculas até então inalcançáveis sinteticamente puderam ser obtidas de forma eficiente e quimiosseletiva a partir de reagentes simples. As reações de acoplamento cruzado, como alguns desses processos são chamados, têm ganhado destaque desde as publicações originais de Suzuki-Miyaura, Kumada-Tamao-Corriu, Mizoroki-Heck, Sonogashira, Stille -durante a década de 1970 -e de Hiyama -em 1988. Desde então são numerosos os esforços feitos por cientistas do mundo todo no sentido de não apenas entender melhor tais processos, mas também desenvolver novos sistemas catalíticos mais eficientes e aplicáveis a uma maior variedade de substratos e aos conceitos da Química Verde. Este trabalho objetiva expor alguns dos avanços publicados por cientistas ao redor do mundo, nos últimos seis anos, com base neste tema.

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“…Diese Toleranz gegenüber OH-und NH-Gruppen wurde besonders ausführlich in Bezug auf Organozinkreagentien untersucht. [53,54] Folglich ermçg-licht ein adäquates Pd-Katalysatorsystem vielfältige Kreuzkupplungen der Organozinkverbindungen 34-36 mit Arylbromiden oder -iodiden, die NH 2 -, RNH-Gruppen bzw. eine sekundäre Alkoholfunktion tragen.…”

Section: Die Frage Der Chemoselektivitätunclassified

Regio‐ und chemoselektive Metallierung von Arenen und Heteroarenen mit gehinderten Metallamidbasen

et al. 2011

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Die Synthese hoch funktionalisierter Organometallverbindungen gelingt durch C‐H‐Aktivierung zahlreicher ungesättigter Substrate mit Lithiumchlorid‐solubilisierten 2,2,6,6‐Tetramethylpiperidyl‐Basen (TMPnMXm⋅p LiCl). Diese Reagentien erweisen sich als exzellent zur Umwandlung vielfältiger aromatischer sowie heterocyclischer Substrate in nützliche metallorganische Reagentien mit weiter Anwendungsbreite in der organischen Synthese.

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Negishi Cross‐Couplings Compatible with Unprotected Amide Functions

Cited by 71 publications

References 32 publications

Exposing the hidden complexity of stoichiometric and catalytic metathesis reactions by elucidation of Mg-Zn hybrids

Exposing the hidden complexity of stoichiometric and catalytic metathesis reactions by elucidation of Mg-Zn hybrids

C-C Cross-Coupling: New Methodologies, Applications and Discoveries over the Last Few Years

Regio‐ und chemoselektive Metallierung von Arenen und Heteroarenen mit gehinderten Metallamidbasen

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