Secondary Alkyl Halides in Transition‐Metal‐Catalyzed Cross‐Coupling Reactions

Rudolph, Alena; Lautens, Mark

doi:10.1002/anie.200803611

Cited by 763 publications

(293 citation statements)

References 106 publications

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“…[1][2][3][4] However, the mechanistic understanding of these reactions is still limited. There is ample evidence that most coupling involves alkyl radicals originated from alkyl halides.…”

Section: Introductionmentioning

confidence: 99%

Bimetallic Oxidative Addition in Nickel-Catalyzed Alkyl–Aryl Kumada Coupling Reactions

Breitenfeld

Wodrich

2014

Organometallics

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“…[1][2][3][4] However, the mechanistic understanding of these reactions is still limited. There is ample evidence that most coupling involves alkyl radicals originated from alkyl halides.…”

Section: Introductionmentioning

confidence: 99%

Bimetallic Oxidative Addition in Nickel-Catalyzed Alkyl–Aryl Kumada Coupling Reactions

Breitenfeld

Wodrich

2014

Organometallics

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“…While screening palladium sources,w eo bserved that the rearrangement did not occur when we used [Pd(MeCN) 4 ]-(BF 4 ) 2 instead of Pd(TFA) 2 .I nt he absence of ab ase,t he treatment of aminoalkene 7 with [Pd(MeCN) 4 ](BF 4 ) 2 afforded primary alkyl complex 8,a sam ixture of two rotamers (Scheme 3). Protonation of the amide oxygen atom prevents its chelation to Pd.…”

mentioning

confidence: 99%

Chelation‐Driven Rearrangement of Primary Alkyl Aminopalladation Products to Stable Trisubstituted Alkyl–Palladium Complexes

et al. 2015

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The formation of highly substituted carbon centers using catalysis has been aw idely sought after goal, but complexes of highly substituted carbon atoms with transition metals are rare,and the factors that affect the relative stability of complexes with differentially substituted carbon atoms are poorly understood. In this study,aset of equilibrating alkylpalladium complexes were subtly tuned to form either ap rimary or trisubstituted alkylc omplex as the more thermodynamically favored state,d epending on either the substrate or reaction conditions.A nX -ray crystal structure of the trisubstituted alkyl-palladium complex is presented and compared with the corresponding primary alkylc omplex. The mechanism for rearrangement and the factors that drive the change in stability are discussed.Alkyl-metal complexes are key intermediates in aw ide variety of important organic reactions.[1] Among the more challenging goals of organic synthesis is the formation of highly substituted carbon centers,a nd metal-catalyzed reactions have the potential to be powerful tools in the realization of this goal.[2] However,s uch reactions are still quite challenging because of the scarcity of highly substituted alkyl-metal complexes.U nderstanding the factors that control the structure and stability of alkyl-metal intermediates is critical to expanding the scope of these metal-catalyzed processes.Ther elative stability of primary,s econdary,a nd tertiary alkyl-metal complexes is generally expected to follow the trend for organolithium compounds, [3] in which the highly polarized CÀLi bond results in alarge negative-charge density at the carbon atom. Increasing the substitution of the carbon atom with electron-donating alkyl groups increases the negative charge at the carbon center,a nd thus destabilizes tertiary alkyllithium compounds relative to primary alkyllithium compounds.T his model works well for many alkylmetal complexes,b ut the analysis is more complicated for transition metals such as palladium. Information on the relative stability of alkyl-palladium complexes is sparse, contradictory,a nd without clear general trends.Tw oexperimental studies of the relative stability of alkylpalladium complexes have been reported. Reger et al. [4] studied Pd complexes bearing dithiocarbamate ligands,i n which the small size of the ligands presumably minimizes any steric effects on stability.Inthis study,the stability of the alkyl complexes followed the traditional order:p rimary > secondary @ tertiary.However,alkyl groups bearing electron-withdrawing groups,such as CF 3 or CN,overrode this preference to put those groups next to the PdÀCb ond. More recently, Brookhart and co-workers [5] studied the isomerization of alkyl-palladium complexes with ad iimine ligand. Here,t he relative stability of the alkyl complexes was highly dependent on the structure of the fourth ligand. When no ligand or acetonitrile was bound in cis position to the alkyl ligand, [6] the secondary alkyl complex was more stable,b ut when bulkier ligands were pre...

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“…Obwohl das Auftreten von Radikalen in verschiedenen übergangsmetallkatalysierten Prozessen wie palladiumkatalysierten Reaktionen, [6] Kharasch-Reaktionen [7] oder nickelkatalysierten Kreuzkupplungen [8] mit der Pd I I-Spezies zum Acylpalladium-Intermediat 6 kuppeln kann. Durch Substitution mit einem Nucleophil wird daraus das Produkt freigesetzt und der Katalysator zurück-gebildet.…”

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Radikale und Übergangsmetallkatalyse – eine Allianz par excellence zur Steigerung von Reaktivität und Selektivität in der organischen Chemie

Ford¹,

Jahn²

2009

Angewandte Chemie

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Willkommen in der Radikalkatalyse: Durch Einbindung in Übergangsmetallkatalysezyklen „gezähmte“ Radikale beschleunigen den Gesamtprozess: in Minuten beendete Kumada‐Kupplungen (siehe Schema), hoch regioselektive cobaltkatalysierte Eliminierungen und Markownikow‐Additionen oder durch Titan‐Rhodium‐Systeme katalysierte reduktive Epoxidöffnungen – alle werden durch die hohe Reaktivität von Radikalintermediaten im Zyklus eines übergangsmetallkatalysierten Prozesses angetrieben.

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Secondary Alkyl Halides in Transition‐Metal‐Catalyzed Cross‐Coupling Reactions

Cited by 763 publications

References 106 publications

Bimetallic Oxidative Addition in Nickel-Catalyzed Alkyl–Aryl Kumada Coupling Reactions

Bimetallic Oxidative Addition in Nickel-Catalyzed Alkyl–Aryl Kumada Coupling Reactions

Chelation‐Driven Rearrangement of Primary Alkyl Aminopalladation Products to Stable Trisubstituted Alkyl–Palladium Complexes

Radikale und Übergangsmetallkatalyse – eine Allianz par excellence zur Steigerung von Reaktivität und Selektivität in der organischen Chemie

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