71258-23-6Relevant academic research and scientific papers
Chemo- and regioselective direct hydroxylation of arenes with hydrogen peroxide catalyzed by a divanadium-substituted phosphotungstate
Kamata, Keigo,Yamaura, Taiyo,Mizuno, Noritaka
supporting information; experimental part, p. 7275 - 7278 (2012/08/28)
Peroxide in, phenol out: The catalyst [-PW10O38V 2(μ-OH)2]3- showed high activity in the hydroxylation of various aromatic compounds with aqueous H2O 2. The system was regioselective, producing para-phenols from monosubstituted benzene derivatives. Furthermore, alkylarenes with reactive side-chain Ca spa 3-H bonds could be chemoselectively hydroxylated without significant formation of side-chain oxygenated products. Copyright
Aromatic Hydroxylation at a Non-Heme Iron Center: Observed Intermediates and Insights into the Nature of the Active Species
Makhlynets, Olga V.,Rybak-Akimova, Elena V.
supporting information; experimental part, p. 13995 - 14006 (2011/04/12)
Mechanism of substrate oxidations with hydrogen peroxide in the presence of a highly reactive, biomimetic, iron aminopyridine complex, [Fe II(bpmen)(CH3CN)2][ClO4] 2 (1; bpmen=N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)ethane-1,2- diamine), is elucidated. Complex 1 has been shown to be an excellent catalyst for epoxidation and functional-group-directed aromatic hydroxylation using H2O2, although its mechanism of action remains largely unknown.1, 2 Efficient intermolecular hydroxylation of unfunctionalized benzene and substituted benzenes with H2O2 in the presence of 1 is found in the present work. Detailed mechanistic studies of the formation of iron(III)-phenolate products are reported. We have identified, generated in high yield, and experimentally characterized the key FeIII(OOH) intermediate (Imax=560 nm, rhombic EPR signal with g=2.21, 2.14, 1.96) formed by 1 and H2O2. Stopped-flow kinetic studies showed that FeIII(OOH) does not directly hydroxylate the aromatic rings, but undergoes rate-limiting self-decomposition producing transient reactive oxidant. The formation of the reactive species is facilitated by acid-assisted cleavage of the O-O bond in the iron-hydroperoxide intermediate. Acid-assisted benzene hydroxylation with 1 and a mechanistic probe, 2-Methyl-1-phenyl-2-propyl hydroperoxide (MPPH), correlates with O-O bond heterolysis. Independently generated FeIV=O species, which may originate from O-O bond homolysis in FeIII(OOH), proved to be inactive toward aromatic substrates. The reactive oxidant derived from 1 exchanges its oxygen atom with water and electrophilically attacks the aromatic ring (giving rise to an inverse H/D kinetic isotope effect of 0.8). These results have revealed a detailed experimental mechanistic picture of the oxidation reactions catalyzed by 1, based on direct characterization of the intermediates and products, and kinetic analysis of the individual reaction steps. Our detailed understanding of the mechanism of this reaction revealed both similarities and differences between synthetic and enzymatic aromatic hydroxylation reactions.
Achiral deuterated derivatizing agent for enantiomeric analysis of carboxylic acids by NMR in a chiral liquid crystalline solvent
Meddour, Abdelkrim,Courtieu, Jacques
, p. 3635 - 3644 (2007/10/03)
The use of a deuterated 'probe' for the enantiomeric analysis of chiral carboxylic acids is proposed. The probe is the perdeuterobenzyl fragment which can be easily attached to the acid and removed from the corresponding ester. The analysis is performed t
Biosynthesis of defensive allomones in leaf beetle larvae: Stereochemistry of salicylalcohol oxidation in Phratora vitellinae and comparison of enzyme substrate and stereospecificity with alcohol oxidases from several iridoid producing leaf beetles
Veith,Oldham,Dettner,Pasteels,Boland
, p. 429 - 443 (2007/10/03)
(7S)-[2H5]-Salicylalcohol (3) and (7R)-[2H1]-salicylalcohol (5) have been synthesized in order to examine the stereospecificity of salicylalcohol oxidase from the defensive secretion of the salicylaldehyde-producing leaf beetle Phratora vitellinae. Oxidation was found to proceed by selective removal of the C(7)-H(R) hydrogen atom (Re-specificity) to yield salicylaldehyde. (7S)-[2H6]-Benzylalcohol (9) was also oxidized Re-specifically to benzaldehyde, but in much lower yield, indicating the importance of the orthohydroxy group of salicylalcohol in substrate enzyme binding. The stereospecificities of terpenoid oxidases from six species of iridoid-producing leaf beetle were examined using (1R,8R)-[2H2]-8-hydroxygeraniol (10), and were all found to oxidize the substrate Re-specifically. Cross-activity of oxidation was found in a number of species, with P. vitellinae able to oxidize terpenoid (10) and two of the iridoid-producing species able to oxidize salicylalcohol analogue (3), again with Re-specificity. However, when the two substrate analogs were presented together, in equal concentrations, preferential oxidation of the natural analog was observed in each case. The kinetics of oxidation for a number of terpenoid and aromatic alcohols by the defensive secretion of the iridoid-producing leaf beetle Phaedon armoraciae have been studied, revealing a large difference between the rate of (primary, allylic) terpenoid alcohol oxidation and the rate of salicylalcohol oxidation, thus accounting for the observed selectivity.
Photocatalytic Oxidation of Toluene to Benzaldehyde by Molecular Oxygen
Mao, Yun,Bakac, Andreja
, p. 4219 - 4223 (2007/10/03)
The visible light irradiation of aqueous solutions containing toluene, uranyl(VI) ions, and O2 results in the formation of benzaldehyde as a major product.Small amounts of PhCH2OH are also formed.The yields of benzaldehyde are 3 times greater for toluene-h8 than for toluene-d8, but the kinetic isotope effect for the quenching of the excited state *UO2(2+) by toluene is negligible (ktoluene-h8/ktoluene-d8 = 1.2).This and other evidence indicate that the quenching takes place in two parallel pathways.The major one involves the aromatic portion of toluene and leads to the recovery of the reactants.The minor, productive path takes place by hydrogen atom abstraction from the methyl group, followed by the oxidation of PhCH2(.).Cumene, benzyl alcohol, and benzaldehyde react similarly.
Active site dynamics of toluene hydroxylation by cytochrome P-450
Hanzlik,Ling
, p. 3992 - 3997 (2007/10/02)
Rat liver cytochrome P-450 hydroxylates toluene to benzyl alcohol plus o-, m-, and p-cresol. Deuterated toluenes (C6D5CH3, C6D5CD3, PhCD(n)H(3-n)) were incubated under saturating conditions
KINETICS AND MECHANISM OF THE OXYGENATION OF THE BENZYL COMPLEXES >
Favero, Giancarlo,Mohamud, Said Issa,Turco, Aldo,Vettori, Umberto
, p. 407 - 410 (2007/10/02)
The complexes > react rapidly with dioxygen to afford phosphine oxide, benzyl alcohol and benzaldehyde as oxidation products.The clean stoicheiometry of the reaction of the cyanide complex with O2 allowed us to detect the formation of a 1:1 dioxygen adduct, formulated as >, which evolves to the oxidation products.In this report we are particularly concerned with the mechanism of this transformation, primarily based on kinetic techniques.
Photochemistry of Diphenylketyl Radicals: Spectroscopy, Kinetics, and Mechanisms
Johnston, Linda J.,Lougnot, D. J.,Wintgens, Veronique,Scaiano, J. C.
, p. 518 - 524 (2007/10/02)
The photochemistry of the diphenylketyl radical has been examined in nonpolar solutions.Transient studies using two-laser techniques yield an excited-state lifetime of 3.9 ns in toluene at room temperature, while for diphenylketyl-O-d the lifetime is 8.7 ns.Dye laser irradiation (515 nm) in the kethyl's visible absorption band leads to efficient photobleaching with Φbleach=0.27 +/- 0.06 for the parent radical and 0.39 and 0.26 for the 4-methyl and 4-chloro derivatives, respectively.The photobleaching reaction involves the cleavage of the O-H ketyl bond to yield benzophenone and hydrogen atoms; in cyclohexane the latter abstract hydrogen from the solvent to produce molecular hydrogen, which was characterized by Raman spectroscopy.In accordance with this mechanism, two-laser experiments produce lower yields of photoreduction products than the one-laser experiments in which the ketyls are not photobleached.When the ketyl radicals are generated by reaction of tert-butoxy radicals with benzhydrol, dye laser irradiation leads to a large increase in the yield of benzophenone (now a product), although the mechanism here is somewhat more complex due to the quenching of excited ketyl radicals by di-tert-butyl peroxide (kq=1.9E9 M-1s-1).Detailed studies of the fluorescence, isotope effects, temperature effects, and products are also included.
