3383-21-9Relevant academic research and scientific papers
Oxidation of hindered aniline to iminocyclohexa-2,4-dienone by copper(II) complex of an N-substituted bis-benzimidazolyl ligand
Yadav, Anjana,Mathur, Pavan
, p. 62 - 71 (2015)
Copper(II) complex of an N-octylated bis-benzimidazolyl ligand is synthesized and characterized. X-ray diffraction study revealed that copper(II) is in a distorted square-planar environment of two benzimidazolyl imine nitrogens and two nitrato ligands. This complex carries out the oxidation of 2,4,6-tri-tert-butylaniline at room temperature utilizing low amounts of tert-butylhydroperoxide (TBHP) as an alternate source of oxygen. 3,5-Di-tert-butyl-6-iminocyclohexa-2,4-dienone is found to be the major product along with 3,5-di-tert-butylcyclohexa-3,5-diene-1,2-dione. The oxidation products have been isolated and characterized by 1H NMR, 13C NMR and COSY experiments. The catalytic oxidation proceeds via a copper(II)/copper(III) cycle.
Quinone Complexes of Palladium: Synthesis and Characterisation of the Dimer 2> (dbsq=3,5-di-t-butyl-1,2-benzosemiquinone) formed by the Reaction between 3,5-Di-t-butyl-1,2-benzoquinone and Palladium(0)
Fox, Glenn A.,Pierpont, Cortlandt G.
, p. 806 - 807 (1988)
The dimer 2> has been prepared by treating a Pd0-alkene complex, (dba=dibenzylideneacetone), with 3,5-di-t-butyl-1,2-benzoquinone; it has been characterized spectroscopically and by X-ray crystallography.
Extradiol oxidative cleavage of catechols by ferrous and ferric complexes of 1,4,7-triazacyclononane: Insight into the mechanism of the extradiol catechol dioxygenases
Lin,Reid,Bugg
, p. 5030 - 5039 (2001)
The major oxygenation product of catechol by dioxygen in the presence of FeCl2 or FeCl3, 1,4,7-triazacyclononane (TACN), and pyridine in methanol is the extradiol cleavage product 2-hydroxymuconic semi-aldehyde methyl ester (Lin, G.; Reid, G.; Bugg, T. D. H. J. Chem. Soc. Chem. Commun. 2000, 1119-1120). Under these conditions, extradiol cleavage of a range of 3- and 4-substituted catechols with electron-donating substituents is observed. The reaction shows a preference in selectivity and rate for iron(II) rather than iron(III) for the extradiol cleavage, which parallels the selectivity of the extradiol dioxygenase family. The reaction also shows a high selectivity for the macrocyclic ligand, TACN, over a range of other nitrogen- and oxygen-containing macrocycles. Reaction of anaerobically prepared iron-TACN complexes with dioxygen gave the same product as monitored by UV/vis spectroscopy. KO2 is able to oxidize catechols with both electron-donating and electron-withdrawing substituents, implying a different mechanism for extradiol cleavage. Saturation kinetics were observed for catechols, which fit the Michaelis-Menten equation to give kcatapp = 4.8 × 10-3 s-1 for 3-(2′,3′-dihydroxyphenyl)propionic acid. The reaction was also found to proceed using monosodium catecholate in the absence of pyridine, but with different product ratios, giving insight into the acid/base chemistry of extradiol cleavage. In particular, extradiol cleavage in the presence of iron(II) shows a requirement for a proton donor, implying a role for an acidic group in the extradiol dioxygenase active site.
Palladium(II)-catalyzed synthesis of 2-alkoxytetrahydrofurans from allylic alcohols and vinyl ethers: Stereospecificity and catalysis
Kawamura, Yasufumi,Imai, Takuro,Hosokawa, Takahiro
, p. 3110 - 3114 (2006)
The reaction of (E)- or (Z)-cinnamyl alcohol and ethyl vinyl ether with a catalyst consisting of Pd(OAc)2, Cu(OAc)2, and catechol (1:1:2) under O2 gives a good yield of (Z)- or (E)-4-benzylidene-2- ethoxytetrahydrofuran, respectively. Similarly, 2-butoxy-4- exomethylenetetrahydrofuran was obtained from allyl alcohol and butyl vinyl ether. In the case of allyl alcohol, however, the catalysis does not proceed well with forming palladium black, if a relatively large amount of Pd(OAc) 2, such as 0.25 mmol to 0.05 mmol, is used even in a lower palladium/substrate ratio, e.g. 1 mol% concentration of the catalyst. Georg Thieme Verlag Stuttgart.
A unique series of dinuclear transition metal-polyradical complexes with a m-phenylenediamine spacer and their catalytic reactivity
Mukherjee, Soumen,Rentschler, Eva,Weyhermueller, Thomas,Wieghardt, Karl,Chaudhuri, Phalguni
, p. 1828 - 1829 (2003)
A series of dinuclear transition metal complexes with either six or four iminosemiquinone radicals, in which the metal centres are separated by a distance of ～6.8 A, together with their catalytic reactivity is reported.
Solution chemical properties and catecholase-like activity of the copper(II)-Ac-His-His-Gly-His-OH system, a relevant functional model for copper containing oxidases
Jancso,Paksi,Jakab,Gyurcsik,Rockenbauer,Gajda
, p. 3187 - 3194 (2005)
The solution chemical properties, Superoxide dismutase and catecholase activity of the copper(II)-Ac-His-HisGly-His-OH (hhgh) complexes were studied to identify functional and structural models of copper-containing oxidases. The solution speciation was de
Design of a mononuclear copper(II)-phenanthroline complex: Catechol oxidation, DNA cleavage and antitumor properties
Dey, Dhananjay,Das, Subrata,Yadav, Hare Ram,Ranjani, Anandan,Gyathri, Loganathan,Roy, Sanjay,Guin, Partha Sarathi,Dhanasekaran, Dharumadurai,Choudhury, Angshuman Roy,Akbarsha, Mohammad Abdulkader,Biswas, Bhaskar
, p. 106 - 114 (2016)
A mononuclear copper(II) complex [Cu(phen)(OH2)2(NO3)](NO3) (1) [phen = 1,10-phenanthroline] has been synthesized and structurally characterized by different spectroscopic characterization methods including sing
Aerobic oxidation of 2,4,6-tri-tert-butylphenol to quinones catalyzed by copper(II) complexes of an N-octylated bis-benzimidazolyl ligand
Yadav, Anjana,Mathur, Pavan
, p. 206 - 214 (2015)
Abstract Copper(II) complexes of a N-octylated bisbenzimidazolyl ligand are synthesized and characterized. These complexes carry out the oxidative dealkylation of 2,4,6-tri-tertbutylphenol (TTBP) using molecular oxygen to 2,6-ditertbutylbenzoquinone and 4,6-di-tertbutylbenzoquinone. The oxidation proceeds via a phenoxyl radical species detected spectrophotometrically, and by EPR. A reactive copper(II)-dioxygen species is involved that carries out the oxidation reaction. A comparison of the rates of formation of the 4,6-di-tert-butylbenzoquinone versus 2,6-di-tert-butylbenzoquinone suggests that alternative pathway may exist for the formation of the para-quinone derivative. Isolation of an intermediate 4,4′-peroxybis(2,4,6-tri-tert-butylcyclohexa-2,5-dienone species and its structural characterization supports the above contention.
A family of vanadate esters of monoionized and diionized aromatic 1,2-diols: Synthesis, structure, and redox activity
Baruah, Bharat,Das, Samir,Chakravorty, Animesh
, p. 4502 - 4508 (2002)
The concerned diols (general abbreviation, H2L) are catechol (H2L1) and its 3,5-Bu2t derivative (H2L2). Esters of the type VO(xsal)(HL), 2, are obtained by reacting H2L with VO(xsal)(H2O) or VO(xsal)(OMe)(HOMe), where xsal2- is the diionized salicylaldimine of glycine (x = g), L-alanine (x = a), or L-valine (x = v). The reaction of VO(acac)2 with H2L and the salicylaldimine (Hpsal) of 2-picolylamine has furnished VO(psal)(L), 3. In the structures of VO-(gsal)(HL1), 2a, and VO(vsal)(HL2), 2f, the HL- ligand is O,O-chelated, the phenolic oxygen lying trans to the oxo oxygen atom. The xsal2- coligand has a folded structure and the conformation of 2f is exclusively endo. In both 2a and 2f the phenolic oxygen atom is strongly hydrogen bonded (O···O, 2.60 A) to a carboxylic oxygen atom of a neighboring molecule. In VO(psal)(L2)·H2O, 3b, the diionized diol is O,O-chelated to the metal and the water molecule is hydrogen bonded to a phenoxidic oxygen atom (O···O, 2.84 A). The C-O and C-C distances in the V(diol) fragment reveal that 2 is a pure catecholate and 3 is a catecholate-semiquinonate hybrid. In solution each ester gives rise to a single 51V NMR signal (no diastereoisomers), which generally shifts downfield with a decrease in the ester LMCT band energy. The V(V)/V(IV) and catecholate-semiquinonate reduction potentials lie near -0.75 and 0.35, and 1.10 and 0.70 V vs SCE for 2 and 3, respectively. Molecular oxygen reacts smoothly with 2 quantitatively furnishing the corresponding o-quinone, and in the presence of H2L the reaction becomes catalytic. In contrast, type 3 esters are inert to oxygen. The initial binding of O2 to 2 is proposed to occur via hydrogen bonding with chelated HL-.
Employing Linear Tridentate Ligands with Pyrazole End Groups in Catalytic Tyrosinase Model Chemistry: Does Hemilability Matter?
Herzigkeit, Benjamin,Jurgeleit, Ramona,Fl?ser, Benedikt M.,Mei?ner, Nadja E.,Engesser, Tobias A.,N?ther, Christian,Tuczek, Felix
, p. 2258 - 2266 (2019)
Several copper(I) and copper(II) complexes supported by hemilabile bis(pyrazolylmethyl)amine (pzma) ligands are synthesized and structurally characterized. The copper(I) complexes with hexafluoridophosphate or perchlorate anions are employed as catalysts for the tyrosinase-like oxygenation of 2,4-di-tert-butylphenol (DTBP-H). Their activities are comparable to that of [Cu(MeCN)2PMP]PF6 (PMP= pyrazolylmethylpyridine) investigated earlier. In contrast to the copper(I) pzma complexes, their congeners supported by non-hemilabile bis(pyrazolylethyl)amine (pzea) ligands are found to be catalytically inactive.
