Copper complexes pyridine oxide

Furthermore, the presence of bipyridyl increased the selectivity of the copper catalyzed oxidation to peracetic acid. For example, oxidation of propionaldehyde in acetic acid at 30 °C in the presence of [Cu(bipy)2(N03)2] gave the peracid in 58% yield and the acid in yields of 32-40%. When reaction was run using Cu(N03)2 in the absence of bipyridyl, the peracid was formed in 9% yield while the yield of carboxylic acid was 80%. The nature of the amine was varied and the catalytic activity of the copper complex toward oxidation of propionaldehyde varied with the amine as follows bipyridyl, phenanthroline > none, pyridine > 2,9-dimethyl-l, 10-phenan-throline > quinoline > ethylenediamine. The rate equations for oxidation in the presence of Cu(N03)2 and [Cu(bipy)2(N03)2] differed substantially and the apparent activation energies were 8.2 and lO.lkcal/mole, respectively [241]. 

The basic study was performed on copper complexes with N,N,N, N1-tetramethylethane-1,2-diamine (TMED), which were known to be very effective oxidative coupling catalysts (7,12). From our first kinetic studies it appeared that binuclear copper complexes are the active species as in some copper-containing enzymes. By applying the very strongly chelating TMED we were able to isolate crystals of the catalyst and to determine its structure by X-ray diffraction (13). Figure 1 shows this structure for the TMED complex of basic copper chloride Cu(0H)Cl prepared from CuCl by oxidation in moist pyridine. 

Electro-oxidative polymerization of 2,6-disubstituted phenols is listed in Table I, with the polymerizations catalyzed by the copper-pyridine complex and oxidized by lead dioxide. 2,6-Dimethylphenol was electro-oxidatively polymerized to yield poly(2,6-dimethylphen-yleneoxide) with a molecular weight of 10000, as was attained by other polymerization methods. The NMR and IR spectra were in complete agreement with those measured for the other polymerization... 

In ammoniacal solutions of copper salts, the oxidation products are likely to contain nitrogen thus, hexoses give oxalic acid, imidazoles, hydrogen cyanide, and urea. Kinetic studies have been reported for the reaction of Cu(II) in the presence of ammonia with maltose, lactose, melibiose, and cellobiose.190 For the oxidation by tetraamminecopper(II) in ammoniacal and buffered media the rate of reaction is first order in disaccharide concentration, order one-half in ammonia concentration, but it is independent of Cu(II) concentration. The reaction rate is decreased by the addition of ammonium chloride, because of the common ion effect. These kinetics suggested mechanisms involving an intermediate enediolate ion, with the rate of reaction being equal to the rate of enolization.191 A similar mechanism has been proposed for the oxidation of D-fructose by a copper-pyridine complex in an excess of pyridine.192... 

Complexes of metal + ligand + protein or DNA can also catalyze the Diels Alder cycloaddition or oxidations with hydrogen peroxide. Copper complexes bound to DNA catalyzed the Diels-Alder cycloaddition with up to 99% ee [15, 16], Cu(phthalocyanine) complexed to serum albumin also catalyzed the enantioselective (98% ee) Diels-Alder reaction, but only with very high catalyst loading (10 mol%) and only with pyridine-bearing dienophiles (presumably to complex the copper) [17]. Achiral Cr(III) complexes or Mn(Schiff-base) complexes inserted into the active site of apomyoglobin variants catalyzed the sulfoxidation of thio-anisole with up to 13 and 51% ee, respectively [18, 19]. A copper phenanthroline complex attached to the adipocyte lipid-binding protein catalyzed the enantioselective hydrolysis of esters and amides [20]. 

Metallic copper may be oxidized with 9,10-phenanthrenequinone in pyridine solution. By washing the product with ether the bis(9,10-phenanthrenesemiquinone)copper(II) complex (1) is obtained (4). The complex has low solubility in noncoordinating solvents probably due... 

The thermal properties of polyesters are of the greatest importance for their end applications. The important features of a polymer, such as bond strength, inter-and intra-molecular forces, resonance stability, crystallinity, structural imperfections and molecular weight, are responsible for their thermal behaviour. Long oil polyester resin and styrenated polyester resin are made flame retardant by the incorporation of bis-pyridine, bis-tribromophenoxo copper complex and polydibromophenylene oxide. 

Copper complexes in pyridine solution have been shown to be effective catalysts for the oxidative dimerization of aromatic amines to azo compounds [169]. A thorough treatment of oxidative dimerization reactions is beyond the scope of this review. However, recent reports give evidence for copper peroxo complexes [154] in these systems and for the intermediacy of a species of the type,... 

Methyl ethyl ketone, for example is oxidized under mild conditions in the presence of a number of metal complexes in aqueous solution [271-274]. The products of reaction are acetaldehyde and acetic acid. Komissarov and Denisov [272-274] have shown that an iron(III)-o-phenanthroUne complex [272] and a copper(II) pyridine complex [274] catalyze this reaction. In the proposed reaction mechanisms [272, 274] it is suggested that the enolate ion from the ketone is incorporated into the coordination sphere of the metal complex where electron transfer occurs to yield a radical which is attacked by dioxygen, equation (188). In the absence of molecular oxygen, aqueous iron(III) is capable of further oxidizing the radical to form butane 23-dione, equation (189) [271]. 

We developed an alternative to the above described system 116] for the selective aerobic oxidation of primary alcohols to aldehydes based on the combination Cu"Br2(Bpy)-TEMPO (Bpy = 2,2 -bipyridine). The reactions were carried out under air at room temperature in aqueous acetonitrile and were catalyzed by a [copper"(bi-pyridine ligand)] complex and TEMPO and base (KOtBu) as cocatalysts (Eq. (5.15)). 

We found that when using the catalyst system for reaction (4), the amine (in sufficient excess) functioned as base and the copper/amine complex functioned as initiator for reaction (1) as well as catalyzing oxidative coupling. This result differs from the report by Blanchard and coworkers in which reaction (2) could not be initiated by a copper/amine (pyridine)catalyst. The suggested route for reaction is similar to the proposed route for reaction (2) and involves coupling between a phenoxy radical and a monomer anion ... 

CHROMIUM TRIOXIDE-PYRIDINE COMPLEX, preparation in situ, 55, 84 Chrysene, 58,15, 16 fzans-Cinnamaldehyde, 57, 85 Cinnamaldehyde dimethylacetal, 57, 84 Cinnamyl alcohol, 56,105 58, 9 2-Cinnamylthio-2-thiazoline, 56, 82 Citric acid, 58,43 Citronellal, 58, 107, 112 Cleavage of methyl ethers with iodotri-methylsilane, 59, 35 Cobalt(II) acetylacetonate, 57, 13 Conjugate addition of aryl aldehydes, 59, 53 Copper (I) bromide, 58, 52, 54, 56 59,123 COPPER CATALYZED ARYLATION OF /3-DlCARBONYL COMPOUNDS, 58, 52 Copper (I) chloride, 57, 34 Copper (II) chloride, 56, 10 Copper(I) iodide, 55, 105, 123, 124 Copper(I) oxide, 59, 206 Copper(ll) oxide, 56, 10 Copper salts of carboxylic acids, 59, 127 Copper(l) thiophenoxide, 55, 123 59, 210 Copper(l) trifluoromethanesulfonate, 59, 202... 

Copper(II) complexes have been prepared with the 2-acetylpyridine N-oxide 3-azabicyclo[3.2.2.]nonylthiosemicarbazone, 25, and bonding occurs via the pyridine N-oxide oxygen, azomethine nitrogen and thiol sulfur [128]. Based on electronic and ESR spectra, bonding to copper(II) of uninegative, tridentate 25-H is considerably weaker than the related 2-acetylpyridine thiosemicarbazone, 4-H. The other copper(II) complexes reported to date have been prepared... 

Pro-chiral pyridine A-oxides have also been used as substrates in asymmetric processes. Jprgensen and co-workers explored the catalytic asymmetric Mukaiyama aldol reaction between ketene silyl acetals 61 and pyridine A-oxide carboxaldehydes 62 <06CEJ3472>. The process is catalyzed by a copper(II)-bis(oxazoline) complex 63 which gave good yields and diastereoselectivities with up to 99% enantiomeric excess. 

Copper(ii) complexes of 8-amino-7-hydroxy-4-methylcoumarin, 1,10-phenanthroline-2-carboxamide, 2-pyridone, 2,3-di-(2-pyridine N-oxide)-quinoxaline," pyridine carboxylates, l-(2 -pyridyl)-2-azonaphthol, and l-(2 -benzothiazolyl)-2-azonaphthol have also been reported. 

Amines such as diethylamine, morpholine, pyridine, and /V, /V, /V, /V -tetramethylethylene-diamine are used to solubilize the metal salt and increase the pH of the reaction system so as to lower the oxidation potential of the phenol reactant. The polymerization does not proceed if one uses an amine that forms an insoluble metal complex. Some copper-amine catalysts are inactivated by hydrolysis via the water formed as a by-product of polymerization. The presence of a desiccant such as anhydrous magnesium sulfate or 4-A molecular sieve in the reaction mixture prevents this inactivation. Polymerization is terminated by sweeping the reaction system with nitrogen and the catalyst is inactivated and removed by using an aqueous chelating agent. 

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