Selective <i>Ortho</i>‐Hydroxylation–Defluorination of 2‐Fluorophenolates with a Bis(μ‐oxo)dicopper(III) Species

Serrano-Plana, Joan; Garcia‐Bosch, Isaac; Miyake, Ryosuke; Costas, Miguel

doi:10.1002/anie.201405060

Cited by 35 publications

(49 citation statements)

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“…26 Using similar reaction conditions, we found that the S P MeAN oxidized 2,6-F 2 -phenolate to the corresponding 3-F-catechol in moderate yield (30%). Interestingly, coordination of the substrate to S P MeAN (Figure 4 bottom right, brown spectrum) was found to form a phenolate-bound O -type species [(MeAN) 2 Cu III 2 -(O 2− ) 2 (F 2 PhO − )] + ( O MeAN -F 2 PhO − , Figure 4, blue spectrum) with spectroscopic characteristics similar to other phenolate-coordinated O species.…”

Section: Resultsmentioning

confidence: 75%

Substrate and Lewis Acid Coordination Promote O–O Bond Cleavage of an Unreactive L₂Cu^II₂(O₂^2–) Species to Form L₂Cu^III₂(O)₂ Cores with Enhanced Oxidative Reactivity

et al. 2017

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Copper-dependent metalloenzymes are widespread throughout metabolic pathways, coupling the reduction of O2 with the oxidation of organic substrates. Small-molecule synthetic analogs are useful platforms to generate L/Cu/O2 species that reproduce the structural, spectroscopic, and reactive properties of some copper-/O2-dependent enzymes. Landmark studies have shown that the conversion between dicopper(II)-peroxo species (L2CuII2(O22−) either side-on peroxo, SP, or end-on trans-peroxo, TP) and dicopper(III)-bis(μ-oxo) (L2CuIII2(O2−)2:O) can be controlled through ligand design, reaction conditions (temperature, solvent, and counteranion), or substrate coordination. We recently published (J. Am. Chem. Soc. 2012, 134, 8513, DOI: 10.1021/ja300674m) the crystal structure of an unusual SP species [(MeAN)2CuII2(O22−)]2+ (SPMeAN, MeAN: N-methyl-N,N-bis[3-(dimethylamino)propyl]amine) that featured an elongated O–O bond but did not lead to O–O cleavage or reactivity toward external substrates. Herein, we report that SPMeAN can be activated to generate OMeAN and perform the oxidation of external substrates by two complementary strategies: (i) coordination of substituted sodium phenolates to form the substrate-bound OMeAN-RPhO− species that leads to ortho-hydroxylation in a tyrosinase-like fashion and (ii) addition of stoichiometric amounts (1 or 2 equiv) of Lewis acids (LA’s) to form an unprecedented series of O-type species (OMeAN-LA) able to oxidize C–H and O–H bonds. Spectroscopic, computational, and mechanistic studies emphasize the unique plasticity of the SPMeAN core, which combines the assembly of exogenous reagents in the primary (phenolates) and secondary (Lewis acids association to the MeAN ligand) coordination spheres with O–O cleavage. These findings are reminiscent of the strategy followed by several metalloproteins and highlight the possible implication of O-type species in copper-/dioxygen-dependent enzymes such as tyrosinase (Ty) and particulate methane monooxygenase (pMMO).

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Section: Resultsmentioning

confidence: 75%

Substrate and Lewis Acid Coordination Promote O–O Bond Cleavage of an Unreactive L₂Cu^II₂(O₂^2–) Species to Form L₂Cu^III₂(O)₂ Cores with Enhanced Oxidative Reactivity

et al. 2017

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“…By contrast, the side-on peroxide of S P , while susceptible to protonation by acid [35,37,38], is capable of PPh 3 oxidation and can oxidize phenolates to catechols and catechols to quinones through an electrophilic mechanism [34,37]. The O species are the most potent oxidants, capable of phenolate hydroxylation, C-F activation, and C-H activation [2,18,25,39–41]. The extremely compact nature of the T species precludes most reactivity, with the exceptions of proton-coupled electron transfer (PCET) from weak O-H substrates and oxidation of PPh 3 [23,42–44].…”

Section: General Reactivitymentioning

confidence: 99%

High-valent copper in biomimetic and biological oxidations

2016

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A long-standing debate in the Cu-O2 field has revolved around the relevance of the Cu(III) oxidation state in biological redox processes. The proposal of Cu(III) in biology is generally challenged as no spectroscopic or structural evidence exists currently for its presence. The reaction of synthetic Cu(I) complexes with O2 at low temperature in aprotic solvents provides the opportunity to investigate and define the chemical landscape of Cu-O2 species at a small molecule level of detail; eight different types are characterized structurally, three of which contain at least one Cu(III) center. Simple imidazole or histamine ligands are competent in these oxygenation reactions to form Cu(III) complexes. The combination of synthetic structural and reactivity data suggests (i) that Cu(I) should be considered as either a one or two electron reductant reacting with O2, (ii) that Cu(III) reduction potentials of these formed complexes are modest and well within the limits of a protein matrix and (iii) that primary amine and imidazole ligands are surprisingly good at stabilizing Cu(III) centers. These Cu(III) complexes are efficient oxidants for hydroxylating phenolate substrates with reaction hallmarks similar to that performed in biological systems. The remarkable ligation similarity of the synthetic and biological systems makes it difficult to continue to exclude Cu(III) from biological discussions.

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“…A recent example of a C−F hydroxylation reaction mediated by a high-valent copper species is also promoted by a sacrificial reductant. 100 …”

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Direct Observation of a Nonheme Iron(IV)–Oxo Complex That Mediates Aromatic C–F Hydroxylation

et al. 2014

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The synthesis of a pentadentate ligand with strategically designed fluorinated arene groups in the second coordination sphere of a nonheme iron center is reported. The oxidatively resistant fluorine substituents allow for the trapping and characterization of an FeIV(O) complex at −20 °C. Upon warming of the FeIV(O) complex, an unprecedented arene C–F hydroxylation reaction occurs. Computational studies support the finding that substrate orientation is a critical factor in the observed reactivity. This work not only gives rare direct evidence for the participation of an FeIV(O) species in arene hydroxylation but also provides the first example of a high-valent iron–oxo complex that mediates aromatic C–F hydroxylation.

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Selective Ortho‐Hydroxylation–Defluorination of 2‐Fluorophenolates with a Bis(μ‐oxo)dicopper(III) Species

Cited by 35 publications

References 36 publications

Substrate and Lewis Acid Coordination Promote O–O Bond Cleavage of an Unreactive L₂Cu^II₂(O₂^2–) Species to Form L₂Cu^III₂(O)₂ Cores with Enhanced Oxidative Reactivity

Substrate and Lewis Acid Coordination Promote O–O Bond Cleavage of an Unreactive L₂Cu^II₂(O₂^2–) Species to Form L₂Cu^III₂(O)₂ Cores with Enhanced Oxidative Reactivity

High-valent copper in biomimetic and biological oxidations

Direct Observation of a Nonheme Iron(IV)–Oxo Complex That Mediates Aromatic C–F Hydroxylation

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Selective Ortho‐Hydroxylation–Defluorination of 2‐Fluorophenolates with a Bis(μ‐oxo)dicopper(III) Species

Cited by 35 publications

References 36 publications

Substrate and Lewis Acid Coordination Promote O–O Bond Cleavage of an Unreactive L2CuII2(O22–) Species to Form L2CuIII2(O)2 Cores with Enhanced Oxidative Reactivity

Substrate and Lewis Acid Coordination Promote O–O Bond Cleavage of an Unreactive L2CuII2(O22–) Species to Form L2CuIII2(O)2 Cores with Enhanced Oxidative Reactivity

High-valent copper in biomimetic and biological oxidations

Direct Observation of a Nonheme Iron(IV)–Oxo Complex That Mediates Aromatic C–F Hydroxylation

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Substrate and Lewis Acid Coordination Promote O–O Bond Cleavage of an Unreactive L₂Cu^II₂(O₂^2–) Species to Form L₂Cu^III₂(O)₂ Cores with Enhanced Oxidative Reactivity

Substrate and Lewis Acid Coordination Promote O–O Bond Cleavage of an Unreactive L₂Cu^II₂(O₂^2–) Species to Form L₂Cu^III₂(O)₂ Cores with Enhanced Oxidative Reactivity