1020-31-1Relevant articles and documents
Synthesis and antiviral activity of spatially-screened phenols: 1,3-benzoxathiolan-2-one derivatives
Shadyro,Timoshchuk,Polozov,Povalishev,Andreeva,Zhelobkovich
, p. 366 - 369 (1999)
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Substituent effects on the benzene ring. Determination of the intramolecular interactions of substituents in tert-alkyl-substituted catechols from thermochemical measurements
Verevkin, Sergey P.,Schick, Christoph
, p. 946 - 952 (2000)
Chemical equilibria of reactions of transalkylation among tert-butylphenols and tert-butylcatechols in the liquid phase were investigated in the temperature range 373-483 K. The molar enthalpies of fusion ΔcrlH°m of the catechol, 4-tert-butylcatechol, and 3,5-di-tert-butylcatechol were measured by DSC. The standard (p° = 0.1 MPa) molar enthalpies of formation ΔfH°m (cr) at the temperature T = 298.15 K were measured by means of combustion calorimetry for 4-tert-butylcatechol and 3,5-di-tert-butylcatechol. The standard molar enthalpies of sublimation of these compounds, and also the enthalpy of vaporization of 3-tert-butylcatechol, were obtained from the temperature dependence of the vapor pressure measured by the transpiration method. The measured reaction enthalpies were utilized for reconciliation of calorimetrically derived standard molar enthalpies of formation of tert-butyl-substituted phenols and catechols, as a stringent test of thermodynamic consistency of results derived from the diverse techniques employed in this work. Resulting values of ΔfH°m(g) of tert-butylcatechols were obtained at the temperature T = 298.15 K and used to derive their strain enthalpies. The intramolecular interactions of the substituents were discussed in terms of deviations of ΔfH°m(g) from the group additivity rules. No peculiarities in the interaction energy among alkyl groups and the hydroxyl groups in the ortho-, para-, and meta-positions of alkylcatechols in comparison with those of alkyl-substituted phenols were detected. Thus, no new parameters are needed for the prediction of the ΔfH°m(g) values of alkylcatechols by using the group-additive procedure.
Three-way cooperativity in d8 metal complexes with ligands displaying chemical and redox non-innocence
Deibel, Naina,Hohloch, Stephan,Schweinfurth, David,Weisser, Fritz,Grupp, Anita,Sarkar, Biprajit
, p. 15178 - 15187 (2014)
Reversible proton- and electron-transfer steps are crucial for various chemical transformations. The electron-reservoir behavior of redox non-innocent ligands and the proton-reservoir behavior of chemically non-innocent ligands can be cooperatively utilized for substrate bond activation. Although site-decoupled proton- and electron-transfer steps are often found in enzymatic systems, generating model metal complexes with these properties remains challenging. To tackle this issue, we present herein complexes [(cod-H)M(μ-L2-)M(cod-H)] (M=PtII, [1] or PdII, [2], cod=1,5-cyclooctadiene, H2L=2,5-di-[2,6-(diisopropyl)anilino]-1,4-benzoquinone), in which cod acts as a proton reservoir, and L2- as an electron reservoir. Protonation of [2] leads to an unusual tetranuclear complex. However, [1] can be stepwise reversibly protonated with up to two protons on the cod-H ligands, and the protonated forms can be stepwise reversibly reduced with up to two electrons on the L2- ligand. The doubly protonated form of [1] is also shown to react with OMe- leading to an activation of the cod ligands. The site-decoupled proton and electron reservoir sources work in tandem in a three-way cooperative process that results in the transfer of two electrons and two protons to a substrate leading to its double reduction and protonation. These results will possibly provide new insights into developing catalysts for multiple proton- and electron-transfer reactions by using metal complexes of non-innocent ligands.
Bioinspired copper(I) complexes that exhibit monooxygenase and catechol dioxygenase activity
Arnold, Aline,Metzinger, Ramona,Limberg, Christian
, p. 1198 - 1207 (2015)
New tripodal ligand L2 featuring three different pyridyl/imidazolyl-based N-donor units at a bridgehead C atom, from which one of the imidazolyl units is separated by a phenylene linker, was synthesized and investigated with regards to copper(I) complexation. The resulting complex [(L2)Cu]OTf (2OTf), the known complex [(L1)Cu]OTf (1OTf; L1 differs from L2 in that it lacks the phenylene spacer) and [(L3)Cu]OTf (3OTf), prepared from a known chiral, tripodal, N-donor ligand featuring pyridyl, pyrazolyl, and imidazolyl donors, were tested as catalysts for the oxidation of sodium 2,4-di-tert-butylphenolate (NaDTBP) with O2. Indeed, they mediated NaDTBP oxidation to give mainly the corresponding catecholate and quinone (Q). None of the complexes 1OTf, 2OTf, and 3OTf is superior to the others, as yields were comparable and, if the presence of protons is guaranteed by concomitant addition of the phenol DTBP, the oxidation can also be performed catalytically. For all complexes stoichiometric oxidations under certain conditions (concentrated solutions, high NaDTBP content) were found to also generate products typical for metal-mediated intradiol cleavage of the catecholate with O2. As shown representatively for 1OTf this dioxygenation sets in at a later stage of the reaction. Initially a copper species responsible for the monooxygenation must form from 1OTf/NaDTBP/O2, and only thereafter is the copper species responsible for dioxygenation formed and consumes Q as substrate. Hence, under these circumstances complexes 1OTf-3OTf show both monooxygenase and catechol dioxygenase activity.
ORTHO-HYDROXYLATION SELECTIVE DES PHENOLS : I - VERS UN MODELE CHIMIQUE SIMPLE DES TYROSINASES.
Capdevielle, Patrice,Maumy, Michel
, p. 1573 - 1576 (1982)
The oxidation of cuprous phenoxides by molecular oxygen gives rise to catechols and ortho-benzoquinones.Such a new reaction provides a mechanistic approach to tyrosinase catalyzed oxidation of phenols.
Grinstead
, p. 1308,1309 (1964)
Dual oxidase/oxygenase reactivity and resonance Raman spectra of {Cu3O2} moiety with perfluoro-: T -butoxide ligands
Brazeau, Sarah E. N.,Norwine, Emily E.,Hannigan, Steven F.,Orth, Nicole,Ivanovi?-Burmazovi?, Ivana,Rukser, Dieter,Biebl, Florian,Grimm-Lebsanft, Benjamin,Praedel, Gregor,Teubner, Melissa,Rübhausen, Michael,Liebh?user, Patricia,R?sener, Thomas,Stanek, Julia,Hoffmann, Alexander,Herres-Pawlis, Sonja,Doerrer, Linda H.
, p. 6899 - 6909 (2019)
A Cu(i) fully fluorinated O-donor monodentate alkoxide complex, K[Cu(OC4F9)2], was previously shown to form a trinuclear copper-dioxygen species with a {Cu3(μ3-O)2} core, TOC4F9, upon reactivity with O2 at low temperature. Herein is reported a significantly expanded kinetic and mechanistic study of TOC4F9 formation using stopped-flow spectroscopy. The TOC4F9 complex performs catalytic oxidase conversion of hydroquinone (H2Q) to benzoquinone (Q). TOC4F9 also demonstrated hydroxylation of 2,4-di-tert-butylphenolate (DBP) to catecholate, making TOC4F9 the first trinuclear species to perform tyrosinase (both monooxygenase and oxidase) chemistry. Resonance Raman spectra were also obtained for TOC4F9, to our knowledge, the first such spectra for any T species. The mechanism and substrate reactivity of TOC4F9 are compared to those of its bidentate counterpart, TpinF, formed from K[Cu(pinF)(PR3)]. The monodentate derivative has both faster initial formation and more diverse substrate reactivity.
Formation of Hybrid Guanidine-Stabilized Bis(μ-oxo)dicopper Cores in Solution: Electronic and Steric Perturbations
Herres-Pawlis, Sonja,Haase, Roxana,Verma, Pratik,Hoffmann, Alexander,Kang, Peng,Stack, T. Daniel P.
, p. 5426 - 5436 (2015)
A series of new hybrid peralkylated amine-guanidine ligands based on a 1,3-propanediamine backbone and their Cu-O2 chemistry is reported. The copper(I) complexes react readily with O2 at low temperatures in aprotic solvents with weakly coordinating anions to form exclusively bis(μ-oxo)dicopper species (O). Variation of the substituents on each side of the hybrid bidentate ligand reveal that less sterically demanding amine and guanidine substituents increase not only the thermal stability of the formed O cores but also enhance inner-sphere phenolate hydroxylation pathways. TD-DFT analysis on selected guanidine-amine O species suggest that the additional visible-wavelength feature observed is a guanidine π? → Cu2O2 LMCT, which appears along with the classic oxo-σu? → CuIII and πσ? → CuIII LMCT transitions. Variation of the substituents on each side of a hybrid bidentate ligand reveals that less sterically demanding amine and guanidine substituents increase not only the thermal stability of the formed O cores but also enhance inner-sphere phenolate hydroxylation pathways.
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Schulze,Flaig
, p. 231,237 (1952)
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Electron transfer in complexes of BII cations with organic π-acceptors: A combined experimental and quantum-chemical study
Vogler, Daniel,Wolf, Nina,Kaifer, Elisabeth,Himmel, Hans-J?rg
, p. 14354 - 14366 (2019)
Due to their combined Lewis acidity and electron-donor capability, BII cations exhibit an interesting reactivity, which is almost unexplored so far. In this work, we compare the reduction in a dicationic diborane of a series of vicinal diones with different redox potentials, namely 3,5-di-tert-butylbenzoquinone, 3,4,5,6-tetrachlorobenzoquinone, 1,2-naphthalene-dione, 9,10-phenanthrene-dione, 2,2′-dichlorobenzil, benzil and 1,2-acenaphthylene-dione. The experimental work is complemented by quantum-chemical calculations, illuminating the electron-transfer step in the reactions.
Synthesis of some [1,3]benzodioxoles via the reaction of o-quinones with phosphorus ylides
Gautam, Daman R.,Litinas, Konstantinos E.,Fylaktakidou, Konstantina C.,Nicolaides, Demetrios N.
, p. 1851 - 1864 (2003)
3,5-Di(tert-butyl)benzo-1,2-quinone 1c, phenanthrene-9,10-quinone 11, and 1,2-naphthoquinone 18 react with 1-phenylethylidene(triphenyl)phosphorane 2j, cyclopentylidene(triphenyl)phosphorane 2k, cyclohexylidene(triphenyl) phosphorane 21, and tetrahydro-2-furanyl-methylidene(triphenyl)phosphorane 8 to give the corresponding 2-substituted [1,3]benzodioxoles 5-7, 10, 12-14, 20-22 in low to high yields, instead of Wittig products, with exception of 11, 12-dihydro-10H-cyclopenta[b]phenanthro[9,10-d]furan 17. A possible explanation for these reaction sequences is discussed.
Synthesis and properties of 11-(3,5-di-tert-butyl-2-hydroxyphenylcarbamoyl)undecanoic acid, a new amphiphilic antioxidant
Lodyato, Vladimir I.,Yurkova, Irina L.,Sorokin, Viktor L.,Shadyro, Oleg I.,Dolgopalets, Vladimir I.,Kisel, Mikhail A.
, p. 1179 - 1182 (2003)
Based on the membrane addressing concept, designing and synthesis of 11-(3,5-di-tert-butyl-2-hydroxyphenylcarbamoyl)undecanoic acid have been carried out. Antioxidant properties of the prepared compound were investigated in comparison with its non-amphiphilic analogues.
