3425-36-3

Upstream product

• 489-01-0 2,6-Di-t-butyl-4-methoxyphenol 
• 6858-01-1 2,6-di-tert-butyl-4-methylphenoxy radical 
• 131073-58-0 bis(2,6-di-tert-butyl-4-methoxyphenyl) ethanedioate 
• 125189-18-6 (4-methoxy-2,6-di-tert-butylphenoxy)oxalyl chloride 
• 156367-09-8 C₃₀H₄₆N₃O₄P 
• 23531-69-3 α-tocopheroxyl radical 
• 915404-01-2 ²H-O-2,6-di-tert-butyl-4-methoxyphenol 
• 15910-49-3 2,4,6-tri-tert-butyl-4-methoxy-2,5-cyclohexadienone 
• 150-76-5 4-methoxy-phenol 
• 7175-54-4 cumyl peroxy radical 
• 50349-73-0 benzotriazole N-oxyl radical 
• 1169875-48-2 6-trifluoromethyl-1H-1,2,3-benzotriazol-N-oxyl 
• 1169875-50-6 C₇H₆N₃O 
• 1310558-96-3 3-quinazolin-4-one-N-oxyl radical 

Downstream Products

• 1975-15-1 2,6,2',6'-tetra-tert-butyl-4,4'-dimethoxy-4,4'-peroxy-bis-cyclohexa-2,5-dienone 
• 489-01-0 2,6-Di-t-butyl-4-methoxyphenol 
• 6858-01-1 2,6-di-tert-butyl-4-methylphenoxy radical 
• 23531-69-3 α-tocopheroxyl radical 
• 719-22-2 2,6-Di-tert-butyl-1,4-benzoquinone 
• 1222630-28-5 C₁₉H₃₃O₂Te 
• 1222630-29-6 C₂₃H₃₃O₂Te 
• 97496-00-9 C₁₅H₂₅OS 

Relevant academic research and scientific papers

Concerted proton-electron transfer oxidation of phenols and hydrocarbons by a high-valent nickel complex

The high-valent nickel(iii) complex Ni(pyalk)2+ (2) was prepared by oxidation of a nickel(ii) complex, Ni(pyalk)2 (1) (pyalk = 2-pyridyl-2-propanoate). 2 and derivatives were fully characterized by mass spectrometry and X-ray crystallography. Electron paramagnetic resonance spectroscopy and X-ray photoelectron spectroscopy confirm that the oxidation is metal-centered. 2 was found to react with a variety of phenolic and hydrocarbon substrates. A linear correlation between the measured rate constant and the substrate bond dissociation enthalpy (BDE) was found for both phenolic and hydrocarbon substrates. Large H/D kinetic isotope effects were also observed for both sets of substrates. These results suggest that 2 reacts through concerted proton-electron transfer (CPET). Analysis of measured thermodynamic parameters allows us to calculate a bond dissociation free energy (BDFE) of ～91 kcal mol-1 for the O-H bond of the bound pyalk ligand. These findings may shed light onto CPET steps in oxidative catalysis and have implications for ligand design in catalytic systems.

Structure, Spectroscopy, and Reactivity of a Mononuclear Copper Hydroxide Complex in Three Molecular Oxidation States

Structural, spectroscopic, and reactivity studies are presented for an electron transfer series of copper hydroxide complexes supported by a tridentate redox-active ligand. Single crystal X-ray crystallography shows that the mononuclear [CuOH]1+ core is stabilized via intramolecular H-bonds between the H-donors of the ligand and the hydroxide anion when the ligand is in its trianionic form. This complex undergoes two reversible oxidation processes that produce two metastable "high-valent"CuOH species, which can be generated by addition of stoichiometric amounts of 1e- oxidants. These CuOH species are characterized by an array of spectroscopic techniques including UV-vis absorption, electron paramagnetic resonance (EPR), and X-ray absorption spectroscopies (XAS), which together indicate that all redox couples are ligand-localized. The reactivity of the complexes in their higher oxidation states toward substrates with modest O-H bond dissociation energies (e.g., 4-substitued-2,6-di-tert-butylphenols) indicates that these complexes act as 2H+/2e- oxidants, differing from the 1H+/1e- reactivity of well-studied [CuOH]2+ systems.

Hydrogen Atom Transfer Oxidation by a Gold-Hydroxide Complex

AuIII-oxygen adducts have been implicated as intermediates in homogeneous and heterogeneous Au oxidation catalysis, but their reactivity is under-explored. Complex 1, ([AuIII(OH)(terpy)](ClO4)2, (terpy = 2,2′:6′,2-terpyridine), readily oxidized substrates bearing C-H and O-H bonds. Kinetic analysis revealed that the oxidation occurred through a hydrogen atom transfer (HAT) mechanism. Stable radicals were detected and quantified as products of almost quantitative HAT oxidation of alcohols by 1. Our findings highlight the possible role of AuIII-oxygen adducts in oxidation catalysis and the capability of late transition metal-oxygen adducts to perform proton coupled electron transfer.

Correction to "electrochemically Determined O-H Bond Dissociation Free Energies of NiO Electrodes Predict Proton-Coupled Electron Transfer Reactivity" (Journal of the American Chemical Society (2019)141: 38 (14971-14975)Doi: 10.1021/jacs.9b07923)

The aqueous CG value used to calculate the bond dissociation free energy (BDFE) values reported in the published Communication was incorrect due to a sign error in its derivation. This systematic error does not affect the conclusions of the study, as all of the aqueous BDFE values shift together. The correct aqueous CG,H2O value is 52.8 kcal mol?1, as reported by Connelly, Wiedner, and Appel.1 We thank Drs. Wiedner and Appel for helpful discussions regarding this correction. We report here revised equations, tables, and schemes with BDFE values adjusted for the correct aqueous CG,H2O term. Pages 14971 and 14972. Equation 1 has been modified to report the correct aqueous CG term, and eqs 4 and 5, which give BDFE values for NiII(OH)2 and NiIIIO(OH), have also been adjusted accordingly. The revised equations are shown below: BDFE(X?H) = 23.06E(pH 0) + 52.8 kcal mol?1 (1) = } =} ? ? Ni O(OH)/Ni (OH) E 0.99 0.03 V BDFE 75.6 1.0 kcal mol III II 2 1 (4) = } = } ? ? Ni O /Ni O(OH) E 1.36 0.02 V BDFE 84.2 1.0 kcal mol IV 2 III 1 (5) Revised BDFE values for the PCET substrates discussed in the original text are given in Table 1. Page 14973. The BDFE ranges discussed in the original publication were adjusted in a similar manner. Thermodynamically favorable reactions at NiIIIO(OH) are predicted for substrates with X?H BDFE less than 75 kcal mol?1 (and were observed for substrates with X?H BDFE ranging from 61 to 73 kcal mol?1). Thermodynamically unfavorable reactivity is predicted (and was observed) for substrates with X?H BDFE greater than 76 kcal mol?1. The observed equilibrium reactivity with 2,4,6-tBu3PhOH is consistent with both the substrate and NiII(OH)2 having an O?H BDFE of ?75.5 kcal mol?1. The number line in Scheme 1 has been adjusted to reflect the corrected BDFE values, and the revised scheme is shown below. [Formula presented] Supporting Information. The BDFE values reported in Tables S1 and S5 were also adjusted for the correct aqueous CG value. The corrected tables are provided in the complete, revised Supporting Information file.

Hydrogen Atom Abstraction by High-Valent Fe(OH) versus Mn(OH) Porphyrinoid Complexes: Mechanistic Insights from Experimental and Computational Studies

High-valent metal-hydroxide species have been implicated as key intermediates in hydroxylation chemistry catalyzed by heme monooxygenases such as the cytochrome P450s. However, in some classes of P450s, a bifurcation from the typical oxygen rebound pathway is observed, wherein the FeIV(OH)(porphyrin) species carries out a net hydrogen atom transfer reaction to form alkene metabolites. In this work, we examine the hydrogen atom transfer (HAT) reactivity of FeIV(OH)(ttppc) (1), ttppc = 5,10,15-tris(2,4,6-triphenyl)-phenyl corrole, toward substituted phenol derivatives. The iron hydroxide complex 1 reacts with a series of para-substituted 2,6-di-tert-butylphenol derivatives (4-X-2,6-DTBP; X = OMe, Me, Et, H, Ac), with second-order rate constants k2 = 3.6(1)-1.21(3) × 104 M-1 s-1 and yielding linear Hammett and Marcus plot correlations. It is concluded that the rate-determining step for O-H cleavage occurs through a concerted HAT mechanism, based on mechanistic analyses that include a KIE = 2.9(1) and DFT calculations. Comparison of the HAT reactivity of 1 to the analogous Mn complex, MnIV(OH)(ttppc), where only the central metal ion is different, indicates a faster HAT reaction and a steeper Hammett slope for 1. The O-H bond dissociation energy (BDE) of the MIII(HO-H) complexes were estimated from a kinetic analysis to be 85 and 89 kcal mol-1 for Mn and Fe, respectively. These estimated BDEs are closely reproduced by DFT calculations and are discussed in the context of how they influence the overall H atom transfer reactivity.

Intramolecular Hydrogen Bonding Enhances Stability and Reactivity of Mononuclear Cupric Superoxide Complexes

[(L)CuII(O2?-)]+ (i.e., cupric-superoxo) complexes, as the first and/or key reactive intermediates in (bio)chemical Cu-oxidative processes, including in the monooxygenases PHM and DβM, have been systematically stabilized by intramolecular hydrogen bonding within a TMPA ligand-based framework. Also, gradual strengthening of ligand-derived H-bonding dramatically enhances the [(L)CuII(O2?-)]+ reactivity toward hydrogen-atom abstraction (HAA) of phenolic O-H bonds. Spectroscopic properties of the superoxo complexes and their azido analogues, [(L)CuII(N3-)]+, also systematically change as a function of ligand H-bonding capability.

A cobalt(ii) iminoiodane complex and its scandium adduct: Mechanistic promiscuity in hydrogen atom abstraction reactions

In addition to oxometal [Mn+O] and imidometal [Mn+NR] units, transient metal-iodosylarene [M(n-2)+-OIPh] and metal-iminoiodane [M(n-2)+-N(R)IPh] adducts are often invoked as a possible second oxidant responsible for the oxo and imido group transfer reactivity. Although a few metal-iodosylarene adducts have been recently isolated and/or spectroscopically characterized, metal-iminoiodane adducts have remained elusive. Herein, we provide UV-Vis, EPR, NMR, XAS and DFT evidence supporting the formation of a metal-iminoiodane complex 2 and its scandium adduct 2-Sc. 2 and 2-Sc are reactive toward substrates in the hydrogen-atom and nitrene transfer reactions, which confirm their potential as active oxidants in metal-catalyzed oxidative transformations. Oxidation of para-substituted 2,6-di-tert-butylphenols by 2 and 2-Sc can occur by both coupled and uncoupled proton and electron transfer mechanisms; the exact mechanism depends on the nature of the para substituent.

Conformational Change with Steric Interactions Affects the Inner Sphere Component of Concerted Proton-Electron Transfer in a Pyridyl-Appended Radical Cation System

Proton-coupled electron transfer (PCET) model systems combine one-electron oxidants and bases to generate net hydrogen atom acceptors. We have generated two persistent pyridyl-appended radical cations: 10-(pyrid-2-yl)-10H-phenothiazinium (PPT?+) and 3-(pyrid-2-yl)-10-methyl-10H-phenothiazinium (MPTP?+). EPR spectra and corresponding calculations indicate phenothiazinium radical cations with minimal spin on the pyridine nitrogen. Addition of hindered phenols causes the radical cations to decay, and protonated products and the corresponding phenoxyl radicals to form. The ΔG° values for the formation of intermediates (determined through cyclic voltammetry and pKa measurements) rule out a stepwise mechanism, and kinetic isotope effects support concerted proton-electron transfer (CPET) as the mechanism. Calculations indicate that the reaction of PPT?+ + tBu3PhOH undergoes a significant conformational change with steric interactions on the diabatic surface while maintaining the hydrogen bond; in contrast, MPTP?+ + tBu3PhOH maintains its conformation throughout the reaction. This difference is reflected in both experiment and calculations with (Formula presented.) (Formula presented.). Experimental results with 2,6-di-tert-butyl-4-methoxyphenol are similar. Hence, despite the structural similarity between the compounds, differences in the inner sphere component for CPET affect the kinetics.

O-H bond oxidation by a monomeric MnIII-OMe complex

Manganese-containing, mid-valent oxidants (MnIII-OR) that mediate proton-coupled electron-transfer (PCET) reactions are central to a variety of crucial enzymatic processes. The Mn-dependent enzyme lipoxygenase is such an example, where a MnIII-OH unit activates fatty acid substrates for peroxidation by an initial PCET. This present work describes the quantitative generation of the MnIII-OMe complex, [MnIII(OMe)(dpaq)]+ (dpaq = 2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8-yl-acetamidate) via dioxygen activation by [MnII(dpaq)]+ in methanol at 25 °C. The X-ray diffraction structure of [MnIII(OMe)(dpaq)]+ exhibits a Mn-OMe group, with a Mn-O distance of 1.825(4) ?, that is trans to the amide functionality of the dpaq ligand. The [MnIII(OMe)(dpaq)]+ complex is quite stable in solution, with a half-life of 26 days in MeCN at 25 °C. [MnIII(OMe)(dpaq)]+ can activate phenolic O-H bonds with bond dissociation free energies (BDFEs) of less than 79 kcal mol-1 and reacts with the weak O-H bond of TEMPOH (TEMPOH = 2,2′-6,6′-tetramethylpiperidine-1-ol) with a hydrogen/deuterium kinetic isotope effect (H/D KIE) of 1.8 in MeCN at 25 °C. This isotope effect, together with other experimental evidence, is suggestive of a concerted proton-electron transfer (CPET) mechanism for O-H bond oxidation by [MnIII(OMe)(dpaq)]+. A kinetic and thermodynamic comparison of the O-H bond oxidation reactivity of [MnIII(OMe)(dpaq)]+ to other MIII-OR oxidants is presented as an aid to gain more insight into the PCET reactivity of mid-valent oxidants. In contrast to high-valent counterparts, the limited examples of MIII-OR oxidants exhibit smaller H/D KIEs and show weaker dependence of their oxidation rates on the driving force of the PCET reaction with O-H bonds. This journal is

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

The reaction of [CuI(TIPT3tren) (CH3CN)]ClO4 (1) and cumene hydroperoxide (C6H5C(CH3)2OOH, ROOH) at -60°C in CH2Cl2 gave a CuII-alkylperoxide/anilino radical complex 2, the formation of which was confirmed by UV-vis, resonance Raman, EPR, and CSI-mass spectroscopy. The mechanism of formation of 2, as well as its reactivity, has been explored.