Oxidative Coupling Of Phenols Research Articles

The purification and characterization of a unique cytochrome P-450 enzyme from Berberis stolonifera plant cell cultures.

A new cytochrome P-450 enzyme, isolated from Berberis stolonifera plant cell suspension cultures, has been purified to electrophoretic homogeneity. The purified hemoprotein migrated as a single band in sodium dodecyl sulfate polyacrylamide gel electrophoresis with a minimal M(r) = 46,000. The enzyme could be purified to a high specific content of P-450 (18.2 nmol/mg protein) after fast protein liquid chromatofocusing, displaying an isoelectric point of 6.05. Spectral analysis of the homogeneous enzyme showed that it is predominantly low spin in the oxidized state, with a slight red-shifted ferrous carbonyl complex that exhibits a maximum at 452 nm. The purified cytochrome P-450, successfully reconstituted with NADPH-cytochrome P-450 reductase, displayed a maximal turnover rate of 50 nmol of substrate/nmol of P-450/min. In the purified and reconstituted form, the enzyme catalyzed the oxidation of three different chiral benzyltetrahydroisoquinoline substrates, namely (S)-coclaurine, (R)-N-methylcoclaurine, and (S)-N-methylcoclaurine, leading to the formation of three distinct dimeric products, (R,S)-berbamunine, (R,S)-2'-norberbamunine, and (R,R)-guattegaumerine, that are also present in the plant cell cultures in vivo. This is the first report of a P-450 enzyme that mediates regio- and stereoselective intermolecular oxidative phenol coupling to furnish natural dimeric compounds. In this catalytic cycle cytochrome P-450 functions as an oxidant in a bisubstrate reaction without transfer of the activated oxygen atom to either of the two chiral substrates.

Non-classical urea oligomers. Part XIV. Some new properties of Cu(II) ion encircled by bis-branched oligomeric urea ligand: properties associated with catalysis for oxidative coupling of phenols

Bis-branched urea oligomers (B-urea) mainly composed of hexakis( N-arylcarbamoyl)-[ 3 N, 4 N-bis(ethylamino)]pentaethylenehexamine were obtained by the reaction of triethylenetetramine with 1,2-dibromoethane followed by ureanization with PhNCO. Under neutral conditions the B-urea readily forms stable mononuclear Cu(II) complexes in which a Cu(II) ion is almost fully surrounded by the B-urea ligand, as evidenced by magnetic susceptibility measurements. In the presence of oxygen, this Cu(II) complex (B-urea-Cu(II)) effectively catalyzes oxidative coupling of various substituted phenols. At the same time the Cu(II) ion is reduced to form the corresponding yellow B-urea-Cu(I) complex quantitatively. The Cu(I) state is highly stable for storage in the solid state but can readily be reacted with oxygen in a reversible manner in solution.

Oxidative phenol coupling catalyzed by polymer‐bound copper‐imidazole complexes

AbstractPolymer‐bound imidazole‐copper(II) complexes were investigated and applied as catalysts for oxidative coupling (polymerization) of 2,6‐dialkylphenols. These polymeric catalysts were also immobilized on silica particles through adsorption, quaternization and grafting. Especially, the grafted catalysts showed interesting catalytic properties, e.g. good specificity for C‐O coupling and very good stability during prolonged use in continuous processes. This stability furnished new information about the mechanism of the oxidative coupling polymerization. Finally, this reaction was optimized for the preparation of PPO‐type telechelics.

Spectrophotmetric determination of phenolic compounds by flow-injection analysis

Flow-injection procedures for the spectrophotometric determination of phenol by two different colour reactions have been developed. The common 4-aminoatnipyrine (4-AAP) reaction and the oxidative coupling of phenol with 3-methyl-2-benzothiazoline hydrazone (MBTH) are both readily applicable and permit the determination of phenol at a sampling rate of 60 h −1 and a relative standard deviation better than 3%. The sensitivity of the BMTH method is about four times higher that of the 4-AAP reaction, with detection limits of 12 and 30 μg/l phenol, respectively. A study of the response of the two methods to phenol derivatives revealed particular merits and limitations. The 4-AAP reaction prouducts have similar absorbance maxima but the reactivity is comparatively low. MBTH reacts with products differ singificantly, a problem is the appropriate choise of the measuring wavelength.

Protonation of tetranuclear oxo(chloro)pyridinecopper(II) complexes by HBF 4 in nitrobenzene

Tetrafluoroboric acid (HBF 4) and triethylamine (Et 3N) have been added consecutively to solutions of tetranuclear oxocopper(II) complexes (μ 4-O)py 3Cu 4Cl 4O ( Ia), (μ 4-O)py 4Cu 4Cl 4O ( Ib), (μ 4-O)py 3Cu 4Cl 6 ( IIa), (μ-O) 2N 4Cu 4Cl 4 ( IIIa) and (μ 4-O)N 4Cu 4Cl 6( IVa) in nitrobenzene at 25 °C to examine their proton basicities. Here, py is pyridine and N is N, N-diethylnicotinamide. The reactions were assigned from spectral and conductivity data. We conclude that the μ 4-oxo groups of IIa and IVa are reversibly monoprotonated by HBF 4 and are less basic than Et 3N. Further addition of HBF 4 apparently removes the central μ 4-oxo group of IIa and IVa as H 3O + and then protonates coordinated py and N. Complexes Ia, Ib and IIIa are irreversibly monoprotonated at their respective oxo groups, which are more basic than Et 3N. The protonation sequence for Ia consists of loss of its terminal oxo group Cu vO as H 3O +, followed by loss of coordinated py as pyH +. The sequence for Ib is the same except that py coordinated at the v site of Ib is protonated in preference to py at sites x. The μ 4-oxo group of Ia and Ib and the OH groups of diprotonated IIIa are less basic than their respective ligands py and N. Implications of the results on the mechanisms of copper-catalyzed phenolic oxidative coupling reactions are considered.

Isoflavone Dimers from Yeast Extract-Treated Cell Suspension Cultures of Pueraria lobata

Abstract Two new isoflavone dimers, kudzuisoflavone A and B have been isolated from yeast extracttreated cell suspension cultures of Pueraria lobata (Leguminosae). Their structures were characterized by spectral data, and they were considered to be formed by phenol oxidative coupling of two isoflavone moieties through C -C ortho-ortho and ortho-para couplings, respectively.

Effects of transmetalation on the mechanisms of copper-catalyzed phenolic oxidative coupling reactions

The mechanism of initiation of phenolic oxidative coupling by the tetranuclear copper( I) complex [pyCuCl] 4 is affected by transmetalation. [pyCuCl] 4 is stoichiometrically transmetalated by equimolar (M(NS) 2 reagents (M is Co, Ni, Cu or Zn) at room temperature in nitrobenzene under N 2 to give equimolar solutions of air-sensitive complexes py 3Cu 3M(NS)Cl 4 ( IIa-d, respectively) and py and 1 mol of insoluble Cu(NS)(s). The corresponding reaction with equimolar Co(NS) 3 gives equimolar solutions of py 3Cu 3Co(NS) 2Cl 4 ( III) and py and 1 mol of Cu(NS)(s). Here, py is pyridine and NS is monoanionic S-methyl isopropylidenehydrazinecarbodithioate. Second- order reduction of O 2 by [pyCuCl] 4 gives the tetranuclear oxocopper(II) complex (μ- 4-O)py 4Cu 4Cl 4O ( Ib). Reduction of O 2 by IIc in the presence of equimolar py gives Ib and the disulfide co-product N 2S 2. The corresponding reductions of O 2 by IIa, IIb, IId and III give products py 3CuMCl 4O 2 ( IVa, IVb, IVd and IVa, respectively) and N 2S 2. Insertion of O 2 through the Cl 4 cores of the reductants is the rate-determining step in each system. However, different product core structures are indicated by different spectral sensitivity to oxidation co-product N 2S 2 and by different rate laws for their oxidation of 2,6-dimethylphenol (DMPOH) to the corresponding diphenoquinone. These core structures apparently contain either a weakly basic CuOM unit (in IVa and IVb) or a strongly basic Cu v O unit (in Ib and IVd). As a result, the rates of oxidation of DMPOH by Ib and IVd are independent of [DMPOH]. Opening of the CuOM unit to give a weakly basic site M v O is proposed to explain induction periods in the IVa, IVb/DMPOH systems, which then proceed at rates which are proportional to [DMPOH]. The origin of different py 3, 4Cu 3MCl 4O 2 product core structures is discussed.

Ruthenium dioxide in fluoro acid medium: II. Application to the formation of steganes skeleton by oxidative phenolic coupling.

Ruthenium (IV) dioxide dihydrate in fluoro acidic medium was found to be a very efficient agent for the oxidative coupling of the phenolic lignans (±)-presteganes A and B. Different attempts to oxidise the diphenolic dibenzylbutanolide (±)-HPMF were also carried out, but were unsuccessful. Likely explanation for these failures are given.

Formation of the morphine precursor salutaridine is catalyzed by a cytochrome p-450 enzyme in mammalian liver

Abstract A highly regio- and stereoselective microsomal-bound cytochrome P-450 NADPH dependent enzyme has been discovered in pig liver which is responsible for the intramolecular phenol oxidative coupling of (R)-reticuline to salutaridine, thus giving rise to the morphine skeleton in mammals.

ChemInform Abstract: Template‐Directed Phenolic Oxidative Coupling. A Stereocontrolled Route to Spiro Dienones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Electro-organic reactions part 35. Efficient carbon—oxygen bond formation in the anodic coupling of pyridopyrimidine derivatives.

4-H-Pyrido[1,2-a]pyrimidine-2,4-diones (Chichibabin) derivatives, formed by condensation of 2-aminopyridines with substituted dialkylmalonates, are electroactive. In solution in CH 2Cl 2/CF 3CO 2H mixtures they are smoothly and selectively anodically coupled in high yield. The products are novel and unexpected; radical coupling at the C-3 and O-4 positions is involved and the proposed mechanism is analogous to that of oxidative phenolic coupling.

Template-directed phenolic oxidative coupling. A stereocontrolled route to spiro dienones

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTemplate-directed phenolic oxidative coupling. A stereocontrolled route to spiro dienonesJames D. White, Roger J. Butlin, Hoh Gyu Hahn, and Alan T. JohnsonCite this: J. Am. Chem. Soc. 1990, 112, 23, 8595–8596Publication Date (Print):November 1, 1990Publication History Published online1 May 2002Published inissue 1 November 1990https://doi.org/10.1021/ja00179a061RIGHTS & PERMISSIONSArticle Views235Altmetric-Citations19LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (280 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

A Photochemical Route to Oxidative Phenol Coupling

A Photochemical Route to Oxidative Phenol Coupling

ChemInform Abstract: Total Synthesis of (.+‐.)‐11‐O‐Methyl‐caesalpin J and Its C‐13 Epimer.

Abstract The biomimetic total syntheses of racemic 11- O -methyl-caesalpin J ( 9 ) and 13-epi-11- O -methyl-caesalpin J ( 10 ), via phenolic oxidative coupling of the accordingly substituted homoisoflavans 6 and 7 , are described.

Phenolic oxidative coupling with hypervalent organo iodine compound (diacetoxyiodo) benzene

(Diacetoxyiodo) benzene as a phenolic oxidative coupling agent is described.

Phenolic compounds in Bass Strait distillate fuels: their effect on deposit formation

Approximately 100 phenolic compounds have been identified in a caustic extract from catalytically cracked light cycle oil of Bass Strait origin. No other classes of compounds were found in the extract, which contained < 0.5 wt% of sulphur and nitrogen. Addition of the extract to other, more stable distillates caused them to yield increased amounts of total insoluble material during thermal ageing. Infrared spectroscopic evidence indicated that oxidative coupling of the phenols was the most probable mechanism responsible for the increased instability of the fuels. The role of phenolic oxidative coupling, in conjunction with other fuel degradation mechanisms, is discussed.

Metal complex-catalysed phenol coupling of phenolic benzylisoquinoline alkaloids

The proaporphine alkaloid glaziovine (1) was obtained by oxidative phenol coupling from N-methylcoclaurine (2) using tetraphenylporphyrinatomanganese(III) acetate (5) as the catalyst and sodium hypochlorite as the oxidant, or by non-oxidative phenolic coupling using N-methylcoclaurine-8-diazonium salt (8) as substrate and Ru 3(CO) 12 as the catalyst. Both reactions were performed under phase transfer catalysis (PTC). Two aporphine alkaloids (15) and (16) were obtained by oxidative phenol coupling using N-acetylreticuline (14) as substrate, dioxygen as the oxidant and bis(salicylaldehyde) ethylenediiminocobalt(II) (12) as the catalyst.

Spectrum of pollutants in LTC wastewater ‐ A case study

Abstract Low Temperature Carbonization Wastes contain high concentrations of various phenols, organic bases, ammonia, cyanide, thiocyanate and several other constituents of environmental concern. Fresh waste water is colourless to straw‐yellow in colour but changes to red or brownish red due to oxidative coupling of phenols resulting in quinone structures with C‐O‐C linkages.

Phenol oxidative coupling of benzylisoquinoline alkaloids is catalysed by regio- and stereo-selective cytochrome P-450 linked plant enzymes: salutaridine and berbamunine

The alkaloids salutaridine and berbamunine are formed by intramolecular C–C and intermolecular C–O coupling, respectively, catalysed by cytochrome P-450 linked NADPH and O2 dependent microsomal bound plant specific enzymes.

Total synthesis of (±)-11- [formula omitted]-methyl-caesalpin J and its C-13 epimer

The biomimetic total syntheses of racemic 11- O -methyl-caesalpin J ( 9) and 13-epi-11- O -methyl-caesalpin J ( 10), via phenolic oxidative coupling of the accordingly substituted homoisoflavans 6 and 7, are described.