The copper catalysed reaction of sodium methoxide with aryl bromides. A mechanistic study leading to a facile synthesis of anisole derivatives

Aalten, H.L.; Koten, Gerard van; Grove, David M.; Kuilman, T.; Piekstra, O.G.; Hulshof, L.A.; Sheldon, Roger A.

doi:10.1016/s0040-4020(01)89502-8

Cited by 167 publications

(96 citation statements)

References 9 publications

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“…106 A few years later though, van Koten and co-workers systematically studied the copper-catalyzed reaction of sodium methoxide with aryl halides, 59 and reported an alternative mechanism for the same reaction, via intimate-electron transfer, through the Cu(I)-Cu(II) redox couple. In a general overview of these proposals, a potential scheme for the mechanistic pathway via s-bond metathesis can be depicted as in Fig.…”

Section: -105mentioning

confidence: 99%

The mechanism of the modified Ullmann reaction

et al. 2010

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The copper-mediated aromatic nucleophilic substitution reactions developed by Fritz Ullmann and Irma Goldberg required stoichiometric amounts of copper and very high reaction temperatures. Recently, it was found that addition of relatively cheap ligands (diamines, aminoalcohols, diketones, diols) made these reactions truly catalytic, with catalyst amounts as low as 1 mol% or even lower. Since these catalysts are homogeneous, it has opened up the possibility to investigate the mechanism of these modified Ullmann reactions. Most authors agree that Cu(I) is the true catalyst even though Cu(0) and Cu(II) catalysts have also shown to be active. It should be noted however that Cu(I) is capable of reversible disproportionation into Cu(0) and Cu(II). In the first step, the nucleophile displaces the halide in the LnCu(I)X complex forming LnCu(I)ZR (Z = O, NR¢, S). Quite a number of mechanisms have been proposed for the actual reaction of this complex with the aryl halide: 1. Oxidative addition of ArX forming a Cu(III) intermediate followed by reductive elimination; 2. Sigma bond metathesis; in this mechanism copper remains in the Cu(II) oxidation state; 3. Single electron transfer (SET) in which a radical anion of the aryl halide is formed (Cu(I)/Cu(II)); 4. Iodine atom transfer (IAT) to give the aryl radical (Cu(I)/Cu(II)); 5. p-complexation of the aryl halide with the Cu(I) complex, which is thought to enable the nucleophilic substitution reaction. Initially, the radical type mechanisms 3 and 4 where discounted based on the fact that radical clock-type experiments with ortho-allyl aryl halides failed to give the cyclised products. However, a recent DFT study by Houk, Buchwald and co-workers shows that the modified Ullmann reaction between aryl iodide and amines or primary alcohols proceeds either via an SET or an IAT mechanism. Van Koten has shown that stalled aminations can be rejuvenated by the addition of Cu(0), which serves to reduce the formed Cu(II) to Cu(I); this also corroborates a Cu(I)/Cu(II) mechanism. Thus the use of radical clock type experiments in these metal catalysed reactions is not reliable. DFT calculations from Hartwig seem to confirm a Cu(I)/Cu(III) type mechanism for the amidation (Goldberg) reaction, although not all possible mechanisms were calculated.

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Section: -105mentioning

confidence: 99%

The mechanism of the modified Ullmann reaction

et al. 2010

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“…The haloarene has been proposed to react with either anionic, two-coordinate cuprates, such as [Cu(OR) 2 ] − , [14] or neutral copper alkoxides, such as CuOR. [15] The C-X bond-cleavage step has been proposed to occur either by oxidative addition of the C-X bond to yield a Cu III intermediate or through a oneelectron transfer from the copper center to the haloarene to yield a haloarene radical anion that undergoes C-X cleavage.…”

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Copper(I) Phenoxide Complexes in the Etherification of Aryl Halides

et al. 2010

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Was ist der richtige Weg? Kupfer(I)‐Phenoxid‐Komplexe mit Chelatliganden (siehe Bild) sind mögliche Intermediate bei Kupfer‐katalysierten Veretherungen von Arylhalogeniden. Sie wurden nun synthetisiert und vollständig charakterisiert. Es wurde demonstriert, dass die isolierten Komplexe in kinetischer und chemischer Hinsicht plausible Zwischenstufen bei der Synthese von Arylphenylethern sind. Ein Verlauf über Radikale wurde experimentell ausgeschlossen.

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“…The absence of these singlets provide strong support in favor of the structure of the compound 7. The acid 8 obtained in 94% yield by the alkaline hydrolysis of the compound 7, was heated following the method of Alten 10 with a saturated solution of sodium methoxide, DMF and copper (I) bromide to afford the desired acid 9 in 93% yield which is superior (90%) to the published report. 7 The overall yield of the acid 9 was 52%.…”

Section: Resultsmentioning

confidence: 96%