Cu(bipy)2+/TEMPO-catalyzed oxidation of alcohols: radical or nonradical mechanism?

@article{Belanzoni2011Cubipy2TEMPOcatalyzedOO,
  title={Cu(bipy)2+/TEMPO-catalyzed oxidation of alcohols: radical or nonradical mechanism?},
  author={Paola Belanzoni and Carine Michel and Evert Jan Baerends},
  journal={Inorganic chemistry},
  year={2011},
  volume={50 23},
  pages={
          11896-904
        }
}
In the oxidation of alcohols with TEMPO as catalyst, the substrate has alternatively been postulated to be oxidized but uncoordinated TEMPO(+) (Semmelhack) or Cu-coordinated TEMPO(•) radical (Sheldon). The reaction with the Cu(bipy)(2+)/TEMPO cocatalyst system has recently been claimed, on the basis of DFT calculations, to not be a radical reaction but to be best viewed as electrophilic attack on the alcohol C-H(α) bond by coordinated TEMPO(+). This mechanism combines elements of the Semmelhack… 
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Mechanism of copper(I)/TEMPO-catalyzed aerobic alcohol oxidation.
TLDR
A mechanistic investigation of the (bpy)Cu(I)/TEMPO/NMI catalyst system is presented, in which the reactivity of benzylic and aliphatic alcohols are compared andCatalytic rate laws, kinetic isotope effects, and spectroscopic data show that reactions of benzymes have different turnover-limiting steps.
Reactivity of TEMPO toward 16- and 17-electron organometallic reaction intermediates: a time-resolved IR study.
TLDR
This study represents the first direct characterization of the mechanism of the reaction of TEMPO with coordinatively unsaturated organometallic complexes, providing valuable insight into its reactions with commonly encountered reaction intermediates.
Mechanism of alcohol oxidation mediated by copper(II) and nitroxyl radicals.
TLDR
The resulting Oppenauer-like reaction pathway further explains experimental trends in the relative reactivity of different classes of alcohols, as well as the different reactivity observed between TEMPO and bicyclic nitroxyls, such as ABNO.
Mechanism of the Copper/TEMPO-Catalyzed Aerobic Oxidation of Alcohols.
Identifying the mechanism of a catalytic reaction is paramount for designing new and improved catalysts. Several alternative catalytic cycles for the copper/2,2,6,6-tetramethylpiperidine-N-oxyl…
Mechanistic Insight into the 2° Alcohol Oxidation Mediated by an Efficient CuI/L-Proline-TEMPO Catalyst—A Density Functional Theory Study
Density functional theory (DFT) calculations have been performed to investigate the 2° alcohol oxidation to acetophenone catalyzed by the CuI/L-Proline-2,2,6,6- tetramethylpiperidinyloxy (TEMPO)…
Mechanistic Insight into the 2 ◦ Alcohol Oxidation Mediated by an Efficient Cu I / L-Proline-TEMPO Catalyst — A Density Functional Theory Study
Density functional theory (DFT) calculations have been performed to investigate the 2◦ alcohol oxidation to acetophenone catalyzed by the CuI/L-Proline-2,2,6,6tetramethylpiperidinyloxy (TEMPO)…
Copper/TEMPO Redox Redux: Analysis of PCET Oxidation of TEMPOH by Copper(II) and the Reaction of TEMPO with Copper(I).
TLDR
Overall, the facility of the proton-coupled oxidation of TEMPOH by CuII salts suggests that this process could contribute to catalyst regeneration under aerobic oxidation conditions.
Electronic Structure of a Cu(II)-Alkoxide Complex Modeling Intermediates in Copper-Catalyzed Alcohol Oxidations.
TLDR
An increased σ interaction in the Cu(II)-OR bond that results in the spectroscopic features is found and lays the basis for further elucidating the mechanism of copper-catalyzed alcohol oxidations.
Tuning the reactivity of TEMPO by coordination to a Lewis acid: isolation and reactivity of MCl3(η1-TEMPO) (M = Fe, Al).
TLDR
Control experiments indicated that neither MCl(3) (M = Al, Fe) nor TEMPO are capable of effecting the oxidation of alcohols independently.
Electronic Structural Analysis of Copper(II)-TEMPO/ABNO Complexes Provides Evidence for Copper(I)-Oxoammonium Character.
TLDR
The emergent electronic structure picture reveals that Cu coordination confers appreciable oxoammonium character to the aminoxyl ligand and has important implications for the mechanism of alcohol oxidation and the underlying basis for cooperativity in this co-catalyst system.
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References

SHOWING 1-10 OF 24 REFERENCES
Mechanistic insight into the alcohol oxidation mediated by an efficient green [CuBr(2)(2,2'-bipy)]-TEMPO catalyst by density functional method.
TLDR
DFT calculations have been performed to investigate the alcohol oxidation to acetaldehyde catalyzed by [CuBr(2)(2,2'-bipy)]-TEMPO and it is found that the path, in which alcohol provides the proton to TEMPO(-) to produce TEMPOH followed by the oxidation of T EMPOH directly to T EMPO by O(2), is favored.
Activation of the C-H bond by electrophilic attack: theoretical study of the reaction mechanism of the aerobic oxidation of alcohols to aldehydes by the Cu(bipy)(2+)/2,2,6,6-tetramethylpiperidinyl-1-oxy cocatalyst system.
TLDR
Electrophilic attack, being common to the particular catalytic system studied in this paper and the well-known biotic and abiotic oxidation catalysis by heme and non-heme complexes of the ferryl (Fe(IV)O(2+)) ion, appears to be a unifying electronic structure principle of C-H(alpha) hydroxylation and oxidation reactions.
Synthesis and reactivity of a transition metal complex containing exclusively TEMPO ligands: Ni(η2-TEMPO)2.
The reaction of Ni(COD)(2) with two equivalents of the TEMPO radical at 68 °C affords the 16 e(-) "bow-tie" complex Ni(η(2)-TEMPO)(2), 1, in 78% yield. Compound 1 reacts with tert-butyl isocyanide…
Room Temperature Aerobic Copper–Catalysed Selective Oxidation of Primary Alcohols to Aldehydes
A novel and very mild method for the oxidation of primary alcohols to aldehydes with excellent conversions has been developed. The reaction is carried out under air at room temperature and is…
Mechanism of the oxidation of alcohols by oxoammonium cations.
The mechanism of the oxidation of primary and secondary alcohols by the oxoammonium cation derived from 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) has been investigated computationally at the…
Oxidative properties of FeO2+: electronic structure and solvation effects.
TLDR
The primary electron accepting orbital in a water environment is the 3sigma*alpha orbital, an antibonding combination of Fe-3d(z(2)) and O-2p(z), which is very low-lying relative to the pi*alpha compared with, for example, the sigma* orbital in O(2) relative to its pi*.
Fluorous biphasic catalysis: synthesis and characterization of copper(I) and copper(II) fluoroponytailed 1,4,7-Rf-TACN and 2,2'-Rf-bipyridine complexes--their catalytic activity in the oxidation of hydrocarbons, olefins, and alcohols, including mechanistic implications.
TLDR
The synthesis and characterization of new copper complexes are presented, and their role, as precatalysts, in the FBC oxidation of hydrocarbons, olefins, and alcohols is defined.
Concerning the mechanism of the FeCl3-catalyzed alpha-oxyamination of aldehydes: evidence for a non-SOMO activation pathway.
TLDR
The mechanistic details reported herein indicate that, as has been proposed for previously studied alcohol oxidations, complexation between TEMPO and a simple metal salt leads to electrophilic ionic reactivity.
Spin-state splittings of iron(II) complexes with trispyrazolyl ligands
Copper(II)-catalysed aerobic oxidation of primary alcohols to aldehydes.
[CuBr2(2,2′-bipyridine)] catalyses the selective and very mild aerobic oxidation of primary alcohols to aldehydes in acetonitrile : water (2 : 1) in the presence of…
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