24289-60-9Relevant academic research and scientific papers
Effective Oxygenation of 3,5-Di-t-butylpyrocatechol catalysed by Vanadium(III or IV) Complexes
Tatsuno, Yoshitaka,Tatsuda, Masanobu,Otsuka, Sei
, p. 1100 - 1101 (1982)
Oxygenation of 3,5-di-t-butylpyrocatechol (1) to the corresponding muconic acid anhydride (2) and 2-pyrone (3) is efficiently catalysed by vanadium(III or IV) complexes.
Determining the TiO2-photocatalytic aryl-ring-opening mechanism in aqueous solution using oxygen-18 labeled O2 and H2O
Pang, Xibin,Chang, Wei,Chen, Chuncheng,Ji, Hongwei,Ma, Wanhong,Zhao, Jincai
, p. 8714 - 8721 (2014)
The molecules O2 and H2O dominate the cleavage of aromatic sp2 C-C bonds, a crucial step in the degradation of aromatic pollutants in aqueous TiO2 photocatalysis, but their precise roles in this process have remained elusive. This can be attributed to the complex oxidative species involved and to a lack of available models for reactions with a high yield of direct products. Here, we used oxygen-18 isotope labeled O 2 and H2O to observe the aromatic ring-opening reaction of the model compound 3,5-di-tert-butylcatechol (DTBC), which was mediated by TiO2 photocatalysis in an aqueous acetonitrile solution. By analyzing the primary intermediate products (～75% yield), especially the seven-membered ring anhydrides that were formed, we obtained direct evidence for the oxygen atom of dioxygen insertion into a C-C bond of the aromatic ring. This indicates that molecular oxygen is the ultimate ring-opening agent in TiO2 photocatalysis and that it undergoes single O atom incorporation rather than the previously proposed molecular oxygen 1,2-addition processes. The ratio of intradiol to extradiol products depends on the particle size of TiO2 catalysts used, which suggests that the O2 activation is correlated with the available coordination sites on the TiO2 surface in the photocatalytic cleavage of the aromatic ring.
VANADIUM-CATECHOLATO COMPLEXES AS REACTION INTERMEDIATES IN THE VANADIUM CATALYZED OXYGENATION OF CATECHOLS
Tatsuno, Yoshitaka,Tatsuda, Masanobu,Otsuka, Sei,Tani, Kazuhide
, p. 1209 - 1212 (1984)
New vanadium-catecholato complexes containing a Schiff base ligand, (V(salen)(DBcatH)2)*1/2 CH2Cl2, (V(salen)(DBpyrH2)2)*1/2 H2O, (V(salen)(cat))*1/10 CH2Cl2, (V(salen)(Bcat))*H2O, (V(saldpt)(DB-catH))*CH2Cl2 were prepared and characterized by elemental analyses and spectroscopic methods.Their relationship to the vanadium(III or IV)-catalyzed oxygenation of catechol was discussed.
A highly reactive functional model for catechol 1,2-dioxygenase: Reactivity studies of iron(III) catecholate complexes of bis[(2-pyridyl)methyl][(1-methylimidazol-2-yl)methyl]amine
Duda, Mark,Pascaly, Matthias,Krebs, Bernt
, p. 835 - 836 (1997)
The system consisting of an iron(III) salt and bis[(2-pyridyl)-methyl][(1-methylimidazol-2-yl)methyl]amine (bpia) in methanol reacts with various catechols with insertion of dioxygen; in the case of 3,5-di-tert-butylcatechol the efficient catalytic activity of the system is shown.
Kinetic and mechanistic studies of vanadium-based, extended catalytic lifetime catechol dioxygenases
Yin, Cindy-Xing,Finke, Richard G.
, p. 13988 - 13996 (2005)
Recently we showed that V-containing polyoxometalates such as (n-Bu 4N)7SiW9V3O40 or (n-Bu4N)9P2W15V3O 62, as well as eight other V-containing precatalysts tested, evolve to high-activity, long catalytic lifetime (≥30 000-100 000 total turnovers) 3,5-di-tert-butylcatechol (DTBC) dioxygenases in which Pierpont's complex [VO(DBSQ)(DTBC)]2 is apparently a common catalyst resting state [Yin, C.-X.; Finke, R. G. J. Am. Chem. Soc. 2005, 107, 9003-9013]. In a separate paper, autoxidation of DTBC to the corresponding benzoquinone and H 2O2 was shown to be a key to the catalyst evolution process: the H2O2, DTBC, and O2 plus virtually any V-based precatalyst tested form [VO(DBSQ)(DTBC)]2 under the catalytic conditions, that catalyst formation process being autocatalytic in H2O2. The resulting novel concept is that of an autoxidation-product-initiated dioxygenase [Yin, C.-X.; Sasaki, Y.; Finke, R. G. Inorg Chem. 2005, in press]. Herein the following questions about this record catalytic lifetime 3,5-di-tert-butylcatechol dioxygenase catalyst are explored: (i) What is the rate law for 3,5-di-tert-butylcatechol dioxygenation when one begins with Pierpont's [VO(DBSQ)(DTBC)]2? (ii) Does it support the hypothesis that this complex is a catalyst resting state or, perhaps, even the true catalyst? (iii) Can a mechanism be written from that information and from the knowledge in the dioxygenase literature? The results answer each of these questions and provide considerable mechanistic insight into the most catalytically active and long-lived DTBC dioxygenase catalyst presently known.
Oxidation versus dioxygenation of catechol: The iron-bispidine system
Comba, Peter,Wadepohl, Hubert,Wunderlich, Steffen
, p. 5242 - 5249 (2011)
The iron-bispidine-catalyzed oxidation and dioxygenation (catechol dioxygenase activity) [i.e., the oxidation of 3,5-di-tert-butylcatecholate (dbc2-) by [FeII(L)X2]n+ (L = 3,7-dimethyl-9-oxo-2,4-bis(2-pyridyl)-3,7-diazabicyclo[3.3.1]nonane-1, 5-dicarboxylate methyl ester)] and air (O2) was studied experimentally and supported by the analysis of the X-ray crystal structure of [Fe(L·MeOH)(tcc)][B(Ph)4] with the deactivated tetrachlorocatecholate tcc2- and a DFT-based analysis. The [Fe II(L)X2]n+/O2/dbc2- system catalyzes the intradiol cleavage of dbc2- but with a relatively low activity (5 % yield); most of the substrate is oxidized in a two-electron oxidation to the benzoquinone (dbq) product (48 % yield). The crystallographic and DFT-based theoretical analyses indicate that this is due to the high oxidation potential of the FeIII oxidant (fast and efficient electron transfer), that is, the oxidation to the benzoquinone side product is faster, and due to the bonding mode of the catecholate substrate to the FeIII oxidant, with little spin density transferred to the catecholate substrate. The iron-bispidine-catalyzed oxidation and dioxygenation of 3,5-di-tert-butylcatecholate (dbc2-) by [FeII(L)X 2]n+ and air (O2) was studied experimentally and supported by a crystal structure determination and by a DFT-based analysis. The [FeII(L)X2]n+/O2/dbc 2- system catalyzes the intradiol cleavage of dbc2- but only with relatively low activity; most of the substrate is oxidized in a two-electron oxidation to give the benzoquinone (dbq) product. Copyright
A novel iripodal ligand containing three different N-heterocyclic donor functions and its application in catechol dioxygenase mimicking
Wagner, Marit,Limberg, Christian,Tietz, Thomas
, p. 5567 - 5576 (2009)
We describe a novel chiral ligand, L, in which three different Ndonor functions are linked to a methoxymethine unit: a methylpyrazole derivative, a methylimidazole unit, and a pyridyl residue. Complexes with FeCl2, FeBr2, and FeClsu
An all-inorganic, polyoxometalate-based catechol dioxygenase that exhibits > 100 000 catalytic turnovers
Weiner,Finke
, p. 9831 - 9842 (1999)
Following a critical analysis of the dioxygenase literature and injection of the insights therein into the development of new dioxygenase catalysts, two new, of four total exemplary, polyoxoanion precatalysts have been synthesized, characterized, and then discovered to exhibit record catalytic lifetime 3,5-di-tert-butylcatechol (DTBC; 1) dioxygenase activity using molecular oxygen as the terminal oxidant. A total of 24 additional polyoxoanion and other precatalysts have also been surveyed for their DTBC dioxygenase activity. The four exemplary precatalyst complexes are the trivanadium(V)-containing, orange-red parent polyoxoanions (η- Bu4N)7[SiW9V3O40], I, and (η-Bu4N)9[P2W15V3O62], II, and their previously unknown polyoxoanion- supported, dark green iron complexes (n- Bu4N)5[(CH3CN)(x)Fe*SiW9V3O40], III, and (η-Bu4N)5[(CH3CN)(x)Fe* P2W15V3O62], IV. Careful, high (95 ± 5%) mass balance studies are reported, studies rare in the dioxygenase literature, but studies made possible in the case of I-IV by their high activity and long lifetimes which yielded sizable amounts of isolable, and thus unequivocally characterizable, products (the characterization of products 2, 3, 4, and 6 includes single- crystal X-ray crystallography structures): 3,5-di-tert-butyl-1-oxacyclohepta- 3,5-diene-2,7-dione (muconic acid anhydride), 2; 4,6-di-tert-butyl-2H-pyran- 2-one, 3; a new, previously unidentified product (once misidentified in the literature), spiro[1,4-benzodioxin-2(3H), 2'-[2H]pyran]-3-one, 4',6,6',8- tetrakis(1,1-dimethylethyl), 4; 3,5-di-tert-butyl-5-(carboxymethyl)-2- furanone, 5; and the autoxidation product, 3,5-di-tert-butyl-1,2- benzoquinone, 6. Quantitative yields for each of the above products are also reported. Solvent effects on the dioxygenase reaction are evaluated by survey studies in 5 solvents; the highest yields are observed in non-coordinating solvents such as 1,2-dichloroethane. Oxygen uptake studies are reported; the results confirm the 1 O2:1 DTBC stoichiometry which defines a catechol dioxygenase and address, for the first time, the details of how this ~1:1 stoichiometry actually arises from the linear combination of the individual stoichiometries of the five, formally parallel, major reactions yielding the five major products. Initial kinetic studies are also reported; the O2 uptake kinetics reveal a novel product and catalyst evolution mechanism consisting of an A → B induction period, followed by an A + B → 2 B autocatalytic step for complexes I and III, where A = O2 and B is a product of the DTBC plus O2 reaction. Catalyst lifetime experiments with (η- Bu4N)5[(CH3CN)(x)Fe*SiW9V3O40], III, as a prototype precatalyst reveal a DTBC dioxygenase catalytic lifetime of > 100 000 total catalytic turnovers (TTOs), a record compared to any reported dioxygenase, man-made or enzymic. A Summary and Conclusions section is presented, as is a list of the needed additional, in-progress, kinetic, mechanistic, and catalyst isolation and characterization studies. The long-term goal of such studies is the development of even longer-lived, more selective dioxygenase catalysts able to oxygenate the full range of interesting substrates of enzymic dioxygenases, as well as abiological substrates such as propene.
Biomimetic extradiol cleavage of catechols: Insights into the enzyme mechanism
Ito,Que L.
, p. 1342 - 1344 (1997)
Quantitative extradiol cleavage of a catechol derivative is achieved by exposure of complex 1 to O2 in the presence of AgBF4 and an aromatic nitrogen base. These results provide insight into how the regiochemistry of oxidative cleavage may be controlled by the metal centers of the catechol dioxygenases.
Vanadium-based, extended catalytic lifetime catechol dioxygenases: Evidence for a common catalyst
Yin, Cindy-Xing,Finke, Richard G.
, p. 9003 - 9013 (2005)
In 1999, a catechol dioxygenase derived from a V-polyoxometalate was reported which was able to perform a record > 100 000 total turnovers of 3,5-di-tert-butylcatechol oxygenation using O2 as the oxidant (Weiner, H.; Finke, R. G. J. Am. Chem. Soc. 1999, 121, 9831). An important goal is to better understand this and other vanadium-based catechol dioxygenases. Scrutiny of 11 literature reports of vanadium-based catechol dioxygenases yielded the insight that they all proceed with closely similar selectivities. This, in turn, led to a "common catalyst hypothesis" for the broad range of vanadium based catechol dioxygenase precatalysts presently known. The following three classes of V-based compounds, 10 complexes total, have been explored to test the common catalyst hypothesis: (i) six vanadium-based polyoxometalate precatalysts, (n-Bu4N)4H 5PV14O42, (n-Bu4N) 7SiW9V3O40, (n-Bu4N) 5[(CH3CN)xFeII·SiW 9V3O40], (n-Bu4N)9P 2W15V3O62, (n-Bu4N) 5Na2[(CH3CN)xFeII· P2W15V3O62], and (n-Bu 4N)4H2-γ-SiW10V 2O40; (ii) three vanadium catecholate complexes, [V VO(DBSQ)(DTBC)]2, [Et3NH]2[V IVO(DBTC)2]·2CH3OH, and [Na(CH 3-OH)2]2[VV(DTBC)3] 2·4CH3OH (where DBSQ = 3,5-di-tert-butylsemiquinone anion and DTBC = 3,5-di-tert-butylcatecholate dianion), and (iii) simple VO(acac)2. Product selectivity studies, catalytic lifetime tests, electron paramagnetic resonance spectroscopy (EPR), negative ion mode electrospray ionization-mass spectrometry (negative ion ESI-MS), and kinetic studies provided compelling evidence for a common catalyst or catalyst resting state, namely, Pierpont's structurally characterized vanadyl semiquinone catecholate dimer complex, [VO(DBSQ)(DTBC)]2, formed from V-leaching from the precatalysts. The results provide a considerable simplification and unification of a previously disparate literature of V-based catechol dioxygenases.
