Vinylpyridines, oxidation

The immobilization of catalysts or catalyst precursors on solid supports is a common technique for simplifying reaction procedures and/or increasing the stability of the catalyst. The homogeneous MTO catalyst can be transformed into a heterogeneous system in a number of different ways. In a recent approach by Saladino and coworkers, poly(4-vinylpyridine) and poly(4-vinylpyridine) //-oxides were used as the catalyst carrier. The MTO-catalyst obtained from 25% cross-linked poly(4-vinylpyridine) with divinylbenzene proved to catalyze efficiently the formation of even hydrolytically sensitive epoxides in the presence of aqueous hydrogen peroxide (Scheme 11). The catalyst could be recycled up to 5 times without any significant loss of activity. 

Poly(2-vinylpyridine oxide), IV, prevents silicosis, that is, the formation of collagen in the lungs induced by silicate particles. 

The anulability of silica may be relatively high in soils high in humus. There is reported to be an area in Germany where soil contains silidc add in combination with the tannin-like components of humus which is stable at pH 9-10 (144). Rice plants take up. more silica from the growth medium when poly (2-vinylpyridine oxide) is present (145). This is a material which reportedly reduces the toxidty of colloidal or polysilidc add. The nature of the complex formed, if any, is not understood (Chapter 1) unless it is only a pH effect. 

The kinetics of the coherent synchronous reactions of HP decomposition and oxidation of pyridine derivatives has been reported. Regioselective oxidation of the pyridine derivatives were studied and conditions have been optimized for the production of 4-vinylpyridine, 4-vinylpyridine oxide, 2,2 -dipyridyl, and pyridine. A probable synchronized reaction mechanism has been suggested for the decomposition of HP and the free radical chain oxidation of pyridine derivatives. It is suggested that the hydroperoxy radical (H02-radical) plays a key role in this reaction mechanism. The activation energy has been calculated for the elementary steps of the dehydrogenation of 4-ethylpyridine. Oxidation of formamidine disulfide with HP in acidic medium results in the formation... 

Shipment Methods and Packaging. Pyridine (1) and pyridine compounds can be shipped in bulk containers such as tank cars, rail cars, and super-sacks, or in smaller containers like fiber or steel dmms. The appropriate U.S. Department of Transportation (DOT) requirements for labeling are given in Table 4. Certain temperature-sensitive pyridines, such as 2-vinylpyridine (23) and 4-vinylpyridine are shipped cold (<—10°C) to inhibit polymerisation. Piperidine (18) and certain piperidine salts are regulated within the United States by the Dmg Enforcement Agency (DEA) (77). Pyridines subject to facile oxidation, like those containing aldehyde and carbinol functionaUty, can be shipped under an inert atmosphere. 

These results were compared to those obtained with pyridine 1-oxide (9) and poly(4-vinylpyridine 1-oxide) (8) as catalysts. 

If the more activated alkene 2-vinylpyridine is used in place of styrene with the same catalysts and the same range of substrates, anti-Markovnikoff hydroamination is also found. Thus, N-[2-(2 -pyridyl)ethyl]piperidine was isolated in 53% yield from reaction of 2-vinylpyridine with piperidine in the presence of [Rh(COD)2]+/2PPh3 under reflux. N H addition was observed with other amines, the remaining product in all cases being primarily that from oxidative amination (Table 12). When the catalytic reaction was run in the absence of phosphine, the yield of hydroamination product increased dramatically.171... 

Films of [Osn(bpy)2(pvp)i0Cl]Cl348 and [Run(bpy)2(pvp)i0Cl]Cl349 (pvp = poly(4-vinylpyridine)] have been shown active for reductive and oxidative detection of nitrite, respectively. 

A Michael-type addition reaction of phosphine generated from red phosphorus in concentrated aqueous KOH solution has been noted to provide moderate isolable yields of pure organophosphorus products.27 For example, tris-(2-cyanoethyl)phosphine is produced in 45% isolable yield from acrylonitrile, and tris-(2-[y-pyridyl]ethyl) phosphine oxide is isolated in 40% yield from 4-vinylpyridine under these conditions. Excellent yields of the tertiary phosphine oxide, tris-(2-cyanoethyl)phosphine oxide, have been reported using white phosphorus in absolute ethanol with KOH at ice/salt-bath temperatures.28 A variety of solvent systems were examined for this reaction involving a Michael-type addition to acrylonitrile. Similarly, tris-(Z-styryl)phosphine is produced from phenylacetylene under these conditions in 55% isolated yield. It is noteworthy that this last cited reaction involves stereospecific syn- addition of the phosphine to the alkyne. 

Ernst H, Rittinghausen S, Bartsch W, Creutzenberg O, Dasenbrock C, Gorlitz BD, Hecht M, Kairies U, Muhle H, Muller M, Heinrich U, Pott F (2002) Pulmonary inflammation in rats after intratracheal instillation of quartz, amorphousSiO(2),carbon black, and coal dust and the influence of poly-2-vinylpyridine-N-oxide (PVNO). Experimental and Toxicologic Pathology 54 109-126. 

Benzyl alcohol can be smoothly converted to benzaldehyde by electrochemi-cally recycled BrO as an oxidizing catalyst in an emulsion system prepared from a mixture of water, amyl acetate, and 2% BU4NHSO4 [60]. A different hypobromite reagent is provided by an electrochemical oxidation of a cross-linked poly-4-vinylpyridine in an MeCN-H20-HBr-(Pt) system [61]. Secondary alcohols can be oxidized by this method to give ketones in high yields. The electrooxidation of A-monoalkyltosylamides (42) in a two-phase system consisting of cyclohexane... 

It is natural that the participation of N02 and NO+ in the one-electron oxidation puts forward the target of NO2 and NO determination. The direct determination of these gaseous products presents some problems. IR spectroscopy is a method (see, e.g., Todres et al. 1988), but this method is not always convenient or even available. The direct determination of NO2 and NO by ESR spectroscopy is not possible owing to the short relaxation time, which gives rise to broad absorption lines. Spin trapping of NO combined with ESR is recommended for this purpose (Norby et al. 1997). As an effective spin trap for NO2, poly(2-vinylpyridine) has been recently proposed (Davydov et al. 2006). 

H. B. Friedrich, N. Singh, A Study of Poly (4-vinylpyridine)-Supported Ruthenate in the Oxidation of Alcohols, Catal. Lett. 110 (2006) 61—70. 

As shown by their redox potentials oxoruthenium(IV) species containing polypyridyl ligands are strong oxidants and they oxidize a variety of substrates. The complex [Ru(0)(bpy)2(py)] has also been used electrocatalytically for the oxidation of alcohols, aldehydes, alkenes, and aromatics." Electrocatalytic oxidation has also been performed on this complex that has been incorporated into poly-4-vinylpyridine. ... 

A variety of monomers, including styrene, acrylonitrile, (meth) acrylates, (meth) acrylamides, 1,3-dienes, and 4-vinylpyridine, undergo ATRP. ATRP involves a multicomponent system of initiator, an activator catalyst (a transition metal in its lower oxidation state), a deactivator (the transition state metal in its higher oxidation state) either formed spontaneously or deliberately added, ligands, and solvent. Successful ATRP of a specific monomer requires matching the various components so that the dormant species concentration exceeds the propagating radical concentration by a factor of 106. 

The electroreduction of some typically inorganic compoimds such as nitrogen oxides is catalysed by the presence of polymeric osmium complexes such as [Os(bipy)2(PVP)2oCl]Cl, where bipy denotes 2,2 -bipyridyl and PVP poly(4-vinylpyridine). This polymer modifies the reduction kinetics of nitrite relative to the reaction at a bare carbon electrode, and provides calibration graphs of slope 0.197 nA with detection limits of 0.1 pg/mL and excellent short-term reproducibility (RSD = 2.15% for n = 20). The sensor performance was found to scarcely change after 3 weeks of use in a flow system into which 240 standards and 30 meat extracts were injected [195]. 

In 2003, Bernini and coworkers established a method for converting some flavonoid ketones into the corresponding lactones with hydrogen peroxide as oxidant catalyzed by MTO supported on poly(4-vinylpyridine) polymers (equation 82) °. Conversions and... 

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