Generation, Characterization, and Reactivity of a Cu<sup>II</sup>–Alkylperoxide/Anilino Radical Complex: Insight into the O–O Bond Cleavage Mechanism

Paria, Sayantan; Ohta, Takao; Morimoto, Yoshinari; Ogura, Takashi; Sugimoto, Hideki; Fujieda, Nobutaka; Goto, Kei; Asano, Kaori; Suzuki, Takayoshi; Itoh, Shinobu

doi:10.1021/jacs.5b04104

Cited by 30 publications

(27 citation statements)

References 20 publications

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“…194 These assignments were confirmed through comparison to spectra obtained using ligand deuteration on the anilino rings and DFT calculations. The complex is EPR silent, consistent with antiferromagnetic coupling between the radical and the Cu(II) ion.…”

Section: Monocopper Compoundsmentioning

confidence: 71%

“…194 A mechanism for formation of this unusual product was proposed involving initial generation of a [Cu I OOR] complex featuring a protonated aniline arm ( 15 ) and hydrogen bonding from an N–H to the bound peroxide. Heterolytic O–O bond scission and release of ROH would generate the copper(II)-hydroxide ( 17 ), either stepwise via a copper-oxyl intermediate ( 16 ) that then undergoes H atom tautomerization or in concerted fashion.…”

Section: Monocopper Compoundsmentioning

confidence: 99%

“…It is worth noting that heterolytic O–O bond scission and involvement of a ligand donor atom was also observed for 15 (Figure 19). 194 …”

Section: Monocopper Compoundsmentioning

confidence: 99%

“…The unusual [CuOOR] + radical complex 18 194 (Figure 19) cleanly oxidized various para -substituted benzylic alcohols to benzaldehydes (substituents: OMe, Me, F, Cl) in a 2-electron process reminiscent of the copper(II)-phenoxyl unit in galactose oxidase (GAO) 213 and model complexes. 214,215 In the presence of excess substrate, the reaction followed pseudo first-order kinetics, and a Hammett plot of the second-order rate constants had a ρ value of −0.42 ± 0.08, similar to that reported for GAO (−0.09 ± 0.32).…”

Section: Monocopper Compoundsmentioning

confidence: 99%

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Copper–Oxygen Complexes Revisited: Structures, Spectroscopy, and Reactivity

et al. 2017

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A longstanding research goal has been to understand the nature and role of copper–oxygen intermediates within copper-containing enzymes and abiological catalysts. Synthetic chemistry has played a pivotal role in highlighting the viability of proposed intermediates and expanding the library of known copper–oxygen cores. In addition to the number of new complexes that have been synthesized since the previous reviews on this topic in this journal (Mirica, L. M.; Ottenwaelder, X.; Stack, T. D. P. Chem. Rev. 2004, 104, 1013–1046 and Lewis, E. A.; Tolman, W. B. Chem. Rev. 2004, 104, 1047–1076), the field has seen significant expansion in the (1) range of cores synthesized and characterized, (2) amount of mechanistic work performed, particularly in the area of organic substrate oxidation, and (3) use of computational methods for both the corroboration and prediction of proposed intermediates. The scope of this review has been limited to well-characterized examples of copper–oxygen species but seeks to provide a thorough picture of the spectroscopic characteristics and reactivity trends of the copper–oxygen cores discussed.

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Section: Monocopper Compoundsmentioning

confidence: 71%

Section: Monocopper Compoundsmentioning

confidence: 99%

“…It is worth noting that heterolytic O–O bond scission and involvement of a ligand donor atom was also observed for 15 (Figure 19). 194 …”

Section: Monocopper Compoundsmentioning

confidence: 99%

Section: Monocopper Compoundsmentioning

confidence: 99%

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Copper–Oxygen Complexes Revisited: Structures, Spectroscopy, and Reactivity

et al. 2017

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“…On the other hand, if the same species undergoes homolytic cleavage, CumO • is formed and could either (1) undergo intramolecular H • abstraction to give CumOH or (2) undergo β -scission to generate acetophenone. 40,62 …”

Section: Resultsmentioning

confidence: 99%

Decoding the Mechanism of Intramolecular Cu-Directed Hydroxylation of sp³ C–H Bonds

et al. 2017

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The use of copper in directed C−H oxidation has been relatively underexplored. In a seminal example, Schönecker showed that copper and O2 promoted the hydroxylation of steroid-containing ligands. Recently, Baran (J. Am. Chem. Soc. 2015, 137, 13776) improved the reaction conditions to oxidize similar substrates with excellent yields. In both reports, the involvement of Cu2O2 intermediates was suggested. In this collaborative article, we studied the hydroxylation mechanism in great detail, resulting in the overhaul of the previously accepted mechanism and the development of improved reaction conditions. Extensive experimental evidence (spectroscopic characterization, kinetic analysis, intermolecular reactivity, and radical trap experiments) is provided to support each of the elementary steps proposed and the hypothesis that a key mononuclear LCuII(OOR) intermediate undergoes homolytic O−O cleavage to generate reactive RO• species, which are responsible for key C−H hydroxylation within the solvent cage. These key findings allowed the oxidation protocol to be reformulated, leading to improvements of the reaction cost, practicability, and isolated yield.

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A P−P Bond as a Redox Reservoir and an Active Reaction Site

Kim

Lee

2018

Angewandte Chemie

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The carbonylation of a nickel(II) anilido species 2 led to the formation of a dinickel(0)–CO complex (P2P‐PP2){Ni(CO)}2 3 with a P−P bond along with isocyanate generation. In this reaction, the central phosphide moiety of an anionic PPP ligand (PPP−=−P[2‐PiPr2C6H4]2) acts as a single‐electron donor to form a P radical. Alternatively, 3 can be synthesized from the reduction of (PPP)NiCl (1) in the presence of CO; thus, the reaction proceeds by radical coupling of a .P−Ni0−CO species. The reverse reaction occurred to generate 1 when 3 was treated with AgCl. Since the P−P bond is light‐sensitive, its homolysis is possible and was explored by EPR spectroscopy and DFT analysis. Finally, various bond‐activation reactions of 3 occurred under visible‐light conditions, thus indicating that a P−P bond can act as an active reaction site.

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Generation, Characterization, and Reactivity of a Cu^II–Alkylperoxide/Anilino Radical Complex: Insight into the O–O Bond Cleavage Mechanism

Cited by 30 publications

References 20 publications

Copper–Oxygen Complexes Revisited: Structures, Spectroscopy, and Reactivity

Copper–Oxygen Complexes Revisited: Structures, Spectroscopy, and Reactivity

Decoding the Mechanism of Intramolecular Cu-Directed Hydroxylation of sp³ C–H Bonds

A P−P Bond as a Redox Reservoir and an Active Reaction Site

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Generation, Characterization, and Reactivity of a CuII–Alkylperoxide/Anilino Radical Complex: Insight into the O–O Bond Cleavage Mechanism

Cited by 30 publications

References 20 publications

Copper–Oxygen Complexes Revisited: Structures, Spectroscopy, and Reactivity

Copper–Oxygen Complexes Revisited: Structures, Spectroscopy, and Reactivity

Decoding the Mechanism of Intramolecular Cu-Directed Hydroxylation of sp3 C–H Bonds

A P−P Bond as a Redox Reservoir and an Active Reaction Site

Contact Info

Product

Resources

About

Generation, Characterization, and Reactivity of a Cu^II–Alkylperoxide/Anilino Radical Complex: Insight into the O–O Bond Cleavage Mechanism

Decoding the Mechanism of Intramolecular Cu-Directed Hydroxylation of sp³ C–H Bonds