2013
DOI: 10.1021/ja403759x
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Cobalt-Catalyzed Ortho Alkylation of Aromatic Imines with Primary and Secondary Alkyl Halides

Abstract: We report here cobalt-N-heterocyclic carbene catalytic systems for the ortho alkylation of aromatic imines with alkyl chlorides and bromides, which allows the introduction of a variety of primary and secondary alkyl groups at room temperature. The stereochemical outcomes of the reaction of secondary alkyl halides suggest that the present reaction involves single-electron transfer from a cobalt species to the alkyl halide to generate the corresponding alkyl radical. A cycloalkylated product obtained by this met… Show more

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Cited by 160 publications
(71 citation statements)
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“…(2)].T he main limitation is the requirement of an excess of aGrignard reagent, which clearly limits the functional groups tolerated. [66] Thes tereochemical outcome of the reactions involving secondary alkyl halides suggests asingle-electron transfer from ac obalt species to the starting alkyl halide to generate an alkyl radical, although afull mechanistic proposal was not reported. This process was further extended to the use of pivalophenone N À Hi mines,w hich were shown to be excellent benzonitrile surrogates for directed CÀHalkylation, with the corresponding benzonitriles being generated in as ubsequent step either by irradiation in the presence of aperoxide or by reaction with ac atalytic amount of copper(II) acetate under aerobic conditions.…”
Section: Alkylation Of Arylimines With Alkyl Halidesmentioning
confidence: 99%
“…(2)].T he main limitation is the requirement of an excess of aGrignard reagent, which clearly limits the functional groups tolerated. [66] Thes tereochemical outcome of the reactions involving secondary alkyl halides suggests asingle-electron transfer from ac obalt species to the starting alkyl halide to generate an alkyl radical, although afull mechanistic proposal was not reported. This process was further extended to the use of pivalophenone N À Hi mines,w hich were shown to be excellent benzonitrile surrogates for directed CÀHalkylation, with the corresponding benzonitriles being generated in as ubsequent step either by irradiation in the presence of aperoxide or by reaction with ac atalytic amount of copper(II) acetate under aerobic conditions.…”
Section: Alkylation Of Arylimines With Alkyl Halidesmentioning
confidence: 99%
“…51 On the other hand, NHCs were found to be superior ligands to mono-phosphines for the ortho-arylation or benzamides with chloroarenes, 52 smoothly delivering the desired products at RT whereas a reaction temperature of 80 1C was required using PEt 3 as ligand. A similar system was also successfully applied in alkylation reactions with alkyl chloride and bromide coupling partners 53 and in a direct ring-opening process with aziridines. 54 Significant contributions to the field of mild Co-catalyzed C-H activation were also made by the group of Ackermann.…”
Section: Co-based Catalytic Systemsmentioning
confidence: 99%
“…[66] Das stereochemische Ergebnis der Reaktionen mit sekundären Alkylhalogeniden lässt auf einen Einelektronentransfer von einer Cobaltspezies auf das Alkylhalogenid-Startmaterial unter Bildung eines Alkylradikals schließen, wenn auch kein vollständiger mechanistischer Vorschlag unterbreitet wurde. (2)].D ie grçßte Einschränkung war der erforderliche Überschuss an Grignard-Reagens,d er die tolerierten funktionellen Gruppen deutlich begrenzt.…”
Section: Alkylierung Von Aryliminen Mit Alkylhalogenidenunclassified
“…D ie grçßte Einschränkung war der erforderliche Überschuss an Grignard-Reagens,d er die tolerierten funktionellen Gruppen deutlich begrenzt. [66] Das stereochemische Ergebnis der Reaktionen mit sekundären Alkylhalogeniden lässt auf einen Einelektronentransfer von einer Cobaltspezies auf das Alkylhalogenid-Startmaterial unter Bildung eines Alkylradikals schließen, wenn auch kein vollständiger mechanistischer Vorschlag unterbreitet wurde. Dieses Verfahren wurde weiter auf die Umsetzung von Pivalophenon-N-H-Iminen ausgeweitet, die sich als hervorragende Benzonitrilsurrogate fürdirigierte C-H-Alkylierungen erwiesen, bei denen die entsprechenden Benzonitrile in einem Folgeschritt entweder durch Bestrahlung in Gegenwart eines Peroxids oder durch Reaktion mit einer katalytischen Mengen an Kupfer(II)-acetat unter aeroben Bedingungen hergestellt wurden.…”
Section: Alkylierung Von Aryliminen Mit Alkylhalogenidenunclassified