Mechanism of oxidation of the 2-hydroxycyclohexyl radical to cyclopentanecarbaldehyde by copper ions in aqueous solutions

Masarwa, Mohamad; Cohen, Haim; Meyerstein, Dan

doi:10.1021/ic00008a031

Cited by 17 publications

(9 citation statements)

References 6 publications

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“…Cu2+, + Cun-C~C(CHJ2C02H+ + CU+, + cu"'-C~c(cHJ2c02~+4 (21) This mechanism clearly does not describe the process observed due to the fact that it suggests the same final products as the mechanism discussed in section (a) above. Alternatively the oxidation reaction could yield other products directly, e.g., …”

Section: As the Lifetime Of Cun'-ch$(chj2c02p+ Ismentioning

confidence: 88%

Metal Induced Decarboxylation of Aliphatic Free Radicals. I. Kinetics of the Reactions of Copper(I) and Copper(II) Ions with the 2‐Methyl‐2‐Carboxylicacid‐Propyl Free Radical in Aqueous Solutions. A Pulse Radiolysis Study

Masarwa

Cohen

Saar

et al. 1990

Israel Journal of Chemistry

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CH2C(CH3)2CO2H free radicals react with Cu2+aq to form CuIII‐CH2C(CH3)2CO2H2+aq, which probably is rapidly transformed into intermediate I. This intermediate decomposes into Cu+aq + CO2 + CH2=C(CH3)2. This is the first system in which a metal ion induced β‐carboxyl elimination reaction was observed. ·CH2C(CH3)2CO2H free radicals react with CuIII‐CH2C(CH3)2CO2H2+aq to form Cu2+aq and a mixture of (‐CH2C(CH3)2CO2H)2, (CH3)3CCO2H, and HOCH2C(CH3)2CO2H. CH2C(CH3)2CO2H reacts with Cu+aq to form CuII‐CH2C(CH3)2CO2H+aq. The latter intermediate decomposes both via homolysis and by a reaction with Cu2+aq to form 2Cu2+aq + (CH3)3CCO2H. The spectra of the intermediates and the kinetics of reaction are reported.

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Section: As the Lifetime Of Cun'-ch$(chj2c02p+ Ismentioning

confidence: 88%

Metal Induced Decarboxylation of Aliphatic Free Radicals. I. Kinetics of the Reactions of Copper(I) and Copper(II) Ions with the 2‐Methyl‐2‐Carboxylicacid‐Propyl Free Radical in Aqueous Solutions. A Pulse Radiolysis Study

Masarwa

Cohen

Saar

et al. 1990

Israel Journal of Chemistry

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“…It is also relevant to mention the seminal work of Meyerstein, who has investigated the interaction between organic radicals and transition metal complexes, including those of Cu I , carrying out their studies in water or aqueous media. [32][33][34][35][36][37][38][39][40][41][42][43][44] The resulting organocopper transients usually decomposed by protonolysis. 45 In order to learn more about the RRT mechanism and about its impact in an ATRP/OMRP system, we have embarked in a detailed investigation of the nature of the termination products for stabilized radicals interacting with a variety of Cu I complexes in non-aqueous solvents and in the presence of controlled amounts of proton donors.…”

Section: Scheme 4 Ligands Used In This and Previous Studiesmentioning

confidence: 99%

Reductive Termination of Cyanoisopropyl Radicals by Copper(I) Complexes and Proton Donors: Organometallic Intermediates or Coupled Proton–Electron Transfer?

et al. 2019

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Cyanoisopropyl radicals, generated thermally by the decomposition of azobis(isobutyronitrile) (AIBN), participate in reductive radical termination (RRT) under the combined effect of copper(I) complexes and proton donors (water, methanol, triethylammonium salts) in acetonitrile or benzene. The investigated copper complexes were formed in situ from [Cu I (MeCN)4] + BF4in CD3CN or Cu I Br in C6D6 using tris[2-(dimethylamino)ethyl]amine (Me6TREN), tris(2-pyridylmethyl)amine (TPMA) and 2,2'-bipyridine (BIPY) ligands. Upon keeping all other conditions constants, the impact of RRT is much greater for the Me6TREN and TPMA systems than for the BIPY system. RRT scales with the proton donor acidity (Et3NH + >> H2O > CH3OH), it is reduced by deuteration (H2O > D2O and CH3OH > CD3OD) and it is more efficient in C6D6 than in CD3CN. The collective evidence gathered in this study excludes the intervention of an outer-sphere proton-coupled electron transfer (OS-PCET), while an innersphere PCET (IS-PCET) cannot be excluded for coordinating proton donors (water and methanol). On the other hand, the strong impact of RRT for the non-coordinating Et3NH + in CD3CN results from the formation of an intermediate Cu I-radical adduct, suggested by DFT calculations to involve binding via the N atom to yield keteniminato [L/Cu-N=C=CMe2] + derivatives with only partial spin delocalization onto the Cu atom.

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“…A study of the interaction of the 2-hydroxycyclohexyl radical, generated by pulse radiolysis from • OH and cyclohexene, with Cu + aq shows that the resulting organocopper(II) intermediate yields cyclopentanecarbaldehyde as the predominant product. The proposed mechanism of this transformation, shown in Scheme 4, is supported by the observation of deuterium incorporation at position 2 when the reaction was carried out in D2O [96]. On the basis of this study, it was suggested that the previously reported copper-catalyzed oxidation of cyclohexene by persulfate to cyclopentanecarbaldehyde [97] proceeds by formation of this key organocopper(II) transient by interaction with Cu + , even though the steady-state concentration of this ion is rather low, and not as previously proposed via the corresponding organocopper(III) transient.…”

Section: C2 Reactions With Cu + Aqmentioning

confidence: 76%

The interaction of carbon-centered radicals with copper(I) and copper(II) complexes*

Ribelli

Matyjaszewski

Poli

2018

Journal of Coordination Chemistry

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Although alkylcopper(I) reagents are widespread, compounds containing alkyl ligands on Cu II or Cu III are much less common. Such complexes, however, are generated as transient species when carbon-center radicals add to Cu I or Cu II complexes, respectively, and appear to be involved in several copper-catalyzed organic transformations. A few organocopper(II) and organocopper(III) complexes were found sufficiently robust to allow isolation and full characterization. This article reviews the reactivity of carbon-centered radicals with Cu I and Cu II ions, both in aqueous and non-aqueous environments, with focus on the importance of the resulting organocopper species on atom transfer radical polymerization and on copper-catalyzed radical termination.

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Mechanism of oxidation of the 2-hydroxycyclohexyl radical to cyclopentanecarbaldehyde by copper ions in aqueous solutions

Cited by 17 publications

References 6 publications

Metal Induced Decarboxylation of Aliphatic Free Radicals. I. Kinetics of the Reactions of Copper(I) and Copper(II) Ions with the 2‐Methyl‐2‐Carboxylicacid‐Propyl Free Radical in Aqueous Solutions. A Pulse Radiolysis Study

Metal Induced Decarboxylation of Aliphatic Free Radicals. I. Kinetics of the Reactions of Copper(I) and Copper(II) Ions with the 2‐Methyl‐2‐Carboxylicacid‐Propyl Free Radical in Aqueous Solutions. A Pulse Radiolysis Study

Reductive Termination of Cyanoisopropyl Radicals by Copper(I) Complexes and Proton Donors: Organometallic Intermediates or Coupled Proton–Electron Transfer?

The interaction of carbon-centered radicals with copper(I) and copper(II) complexes*

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