Specific Enhancement of Catalytic Activity by a Dicopper Core: Selective Hydroxylation of Benzene to Phenol with Hydrogen Peroxide

Abstract

A dicopper(II) complex, stabilized by the bis(tpa) ligand 1,2-bis[2-[bis(2-pyridylmethyl)aminomethyl]-6-pyridyl]ethane (6-hpa), [Cu (μ-OH)(6-hpa)] , was synthesized and structurally characterized. This complex catalyzed selective hydroxylation of benzene to phenol using H O , thus attaining large turnover numbers (TONs) and high H O efficiency. The TON after 40 hours for the phenol production exceeded 12000 in MeCN at 50 °C under N , the highest value reported for benzene hydroxylation with H O catalyzed by homogeneous complexes. At 22 % benzene conversion, phenol (95.2 %) and p-benzoquinone (4.8 %) were produced. The mechanism of H O activation and benzene hydroxylation is proposed.

Organic–inorganic hybrid of anchored dicationic ionic liquid on Al‐MCM‐41‐phosphovanadomolybdate toward selective oxidation of benzene to phenol

“…Oxidation of C sp2 ‐H and C sp3 ‐H bonds by a catalyst through an oxidant or aerobic oxidation must be one of the most important reactions . Direct Oxidation of benzene to phenol in a simple and a one‐step environmental‐friendly oxidation process is highly desired from both views of environmental and economic and would be a vital alternative for the common industrial cumene process because of its disadvantages . For achieving this goal, various oxidants such as H 2 O 2 , O 2 , N 2 O have been used .…”

Activation of a Non‐Heme FeIII‐OOH by a Second FeIII to Hydroxylate Strong C−H Bonds: Possible Implications for Soluble Methane Monooxygenase

“…These results support an electrophilic aromatic substitution mechanism involving am etal-based electrophile. These results suggest that the oxidant is quite ap otent electrophile.F or both cyclohexane and benzene oxidation, essentially quantitative 18 4 .I nacompetitive oxidation between benzene and cyclohexane,i ti so bserved that hydroxylation of benzene is favored by 10-fold over that for cyclohexane, as found for Sc 3+ and HClO 4 .C umulatively,t hese results suggest that Fe III -(OTf) 3 behaves mechanistically similar to Sc III (OTf) 3 and HClO 4 in forming am etal-based oxidant;h owever, Fe III -(OTf) 3 is more effective than either Sc III (OTf) 3 or HClO 4 in converting cyclohexane to cyclohexanol and benzene to phenol. These results suggest that the oxidant is quite ap otent electrophile.F or both cyclohexane and benzene oxidation, essentially quantitative 18 4 .I nacompetitive oxidation between benzene and cyclohexane,i ti so bserved that hydroxylation of benzene is favored by 10-fold over that for cyclohexane, as found for Sc 3+ and HClO 4 .C umulatively,t hese results suggest that Fe III -(OTf) 3 behaves mechanistically similar to Sc III (OTf) 3 and HClO 4 in forming am etal-based oxidant;h owever, Fe III -(OTf) 3 is more effective than either Sc III (OTf) 3 or HClO 4 in converting cyclohexane to cyclohexanol and benzene to phenol.…”

“…[d]18 Oincorporated into cyclohexanol when H 2 18 O 2 is used or when the reaction is carried out in the presence of H 2 [b] A/K = TON alcohol/ TON ketone.…”

“…These results support an electrophilic aromatic substitution mechanism involving am etal-based electrophile. [16][17][18] Additionally,t he oxidant formed in the presence of Fe 3+ can oxidize electron-poor benzene analogs such as nitrobenzene,b romobenzene and trifluorotoluene,a s revealed by the appearance of chromophores of the corresponding Fe III -OAr products,w hich are blue shifted relative to that of 3 ( Figure S2). These results suggest that the oxidant is quite ap otent electrophile.F or both cyclohexane and benzene oxidation, essentially quantitative 18 4 .I nacompetitive oxidation between benzene and cyclohexane,i ti so bserved that hydroxylation of benzene is favored by 10-fold over that for cyclohexane, as found for Sc 3+ and HClO 4 .C umulatively,t hese results suggest that Fe III -(OTf) 3 behaves mechanistically similar to Sc III (OTf) 3 and HClO 4 in forming am etal-based oxidant;h owever, Fe III -(OTf) 3 is more effective than either Sc III (OTf) 3 or HClO 4 in converting cyclohexane to cyclohexanol and benzene to phenol.…”

“…[c] PKIE = product kinetic isotope effect based on the yields of cyclohexanol and cyclohexanol-d 11 . [d]18 Oincorporated into cyclohexanol when H 2 18 O 2 is used or when the reaction is carried out in the presence of H2 18 O(see SI for further details).…”