4- Phenylpyridine oxide

C-H activation process. The first attempt to explain the mechanism of the cycloruthenation was earned out by Maseras, Dixneuf and co-workers through DFT calculations on the system [Ru(IMe)(Cl)2(2-pyridylbenzene)] using bicarbonate as the base. In this study two different pathways were considered for the cyclometallation of phenylpyridine oxidative addition and the concerted metallation-demetallation mechanism (Scheme 1). 

The nitration of phenylpyridines and related compounds has attracted attention for a long time, and measurements of isomer proportions have been made for several compounds of this type. Nitration occurs in the phenyl ring. For 2-phenylpyridine and 2-phenylpyridine i-oxide measurements of the dependence of rate of nitration upon acidity in 75-81 % sulphuric acid at 25 °C show that both compounds are nitrated as their cations (table 8.1). The isomer distribution did not depend significantly upon the acidity, and by comparison with the kinetic data for quinolinium ( 10.4.2) the partial rate factors illustrated below were obtained.They should be compared with those for the nitration of 2-nitrobiphenyl ( 10.1). The protonated heterocyclic groups are much... 

One of the most significant developmental advances in the Jacobsen-Katsuki epoxidation reaction was the discovery that certain additives can have a profound and often beneficial effect on the reaction. Katsuki first discovered that iV-oxides were particularly beneficial additives. Since then it has become clear that the addition of iV-oxides such as 4-phenylpyridine-iV-oxide (4-PPNO) often increases catalyst turnovers, improves enantioselectivity, diastereoselectivity, and epoxides yields. Other additives that have been found to be especially beneficial under certain conditions are imidazole and cinchona alkaloid derived salts vide infra). 

Conditions (a) 1-5 mol% catalyst, w-CPBA/NMO, -78°C, CH2CI2. (b) 1-5 mol% catalyst, NaOCl, 4-phenylpyridine iV-oxide, 0°C, CH2CI2. (c) 1-5 mol% catalyst, NaOCl, pyridine iV-oxide, 0°C, CH2CI2. (d) Solvent = diethyl ether... 

To a solution of m-ethyl cinnamate (44, 352 mg, 85% pure, 1.70 mmol) and 4-phenylpyridine-A-oxide (85.5 mg, 29 mol%) in 1,2-dichloromethane (4.0 mL) was added catalyst 12 (38.0 mg, 3.5 mol%). The resulting brown solution was cooled to 4°C and then combined with 4.0 mL (8.9 mmol) of pre-cooled bleach solution. The two-phase mixture was stirred for 12 h at 4°C. The reaction mixture was diluted with methyl-t-butyl ether (40 mL) and the organic phase separated, washed with water (2 x 40 mL), brine (40 mL), and then dried over Na2S04. The drying agent was removed by filtration the mother liquors concentrated under reduce pressure. The resulting residue was purified by flash chromatography (silica gel, pet ether/ether = 87 13 v/v) to afford a fraction enriched in cis-epoxide (45, cis/trans . 96 4, 215 mg) and a fraction enriched in trans-epoxide cis/trans 13 87, 54 mg). The combined yield of pure epoxides was 83%. ee of the cis-epoxide was determined to be 92% and the trans-epoxide to be 65%. 

Pyridine has been phenylated with the following free-radical sources benzenediazonium chloride with aluminum trichloride the Gomberg reaction " phenylhydrazine and metal oxides A -nitroso-acetanilide dibenzoyl peroxide phenylazotriphenylmethane di-phenyliodonium hydroxide and electrolysis of benzoic acid. ° Although 2-phenylpyridine usually accounts for over 50% of the total phenylated product, each of the three phenyl derivatives can be obtained from the reaction by fractional recrystallization of the... 

The partial rate factor for nitration of pyridine-N-oxide in the 4 position was estimated as 4x 10"6 which is, therefore, close to that found for the 3 position of pyridine, and 2-phenylpyridine-N-oxide was evaluated as 2xl0-4 times less reactive than benzene from rate measurements in 74.7-78.6 wt. % acid at 25 °C. 

Jacobsen catalyst 4-Phenylpyridine N-oxide Methylen chloride Hexane... 

A variety of transition metal complexes including organometallics was subjected to an ac electrolysis in a simple undivided electrochemical cell, containing only two current-carrying platinum electrodes. The compounds (A) are reduced and oxidized at the same electrode. If the excitation energy of these compounds is smaller than the potential difference of the reduced (A ) and oxidized (A ) forms, back electron transfer may regenerate the complexes in an electronically excited state (A+ + A A + A). Under favorable conditions an electrochemiluminescence (eel) is then observed (A A + hv). A weak eel appeared upon electrolysis o t]jie following complexes Ir(III)-(2-phenylpyridine-C, N ) [Cu(I)(pyridine)i],... 

Rhodium complexes catalyze the oxidative coupling of benzene with ethene to produce styrene directly.45,45a,45b Using Rh(ppy)2(OAc) (ppyH = 2-phenylpyridine), the reaction of benzene with ethene in the presence of 02 and Cu(OAc)2 in benzene and acetic acid at 180 °C gives styrene and vinyl acetate in 77% and 23% selectivities, respectively. 

A 100 mL flask, was filled with (Z)-ethyl cinnamate, (666 mg of the mixture containing 75 % of (Z)-ethyl cinnamate), 4-phenylpyridine N-oxide (116 mg) and dichloromethane (6mL). Jacobsen s catalyst (108 mg) was then added. 

Resolution of a racemic mixture is still a valuable method involving fractional crystallization [113], chiral stationary phase column chromatography [114] and kinetic resolutions. Katsuki and co-workers demonstrated the kinetic resolution of racemic allenes by way of enantiomer-differentiating catalytic oxidation (Scheme 4.73) [115]. Treatment of racemic allenes 283 with 1 equiv. of PhIO and 2 mol% of a chiral (sale-n)manganese(III) complex 284 in the presence of 4-phenylpyridine N-oxide resulted... 

The reactions presented here must not be confused with oxidative reactions that increase bond order and are catalyzed by oxidoreductases, as discussed elsewhere. Examples of the latter reactions include the cytochrome P450 mediated oxidation of testosterone to 6,7-dehydrotestosterone, and the oxidation of l,2,3,6-tetrahydro-l-methyl-4-phenylpyridine to 2,3-dihydro-1-methy 1-4-phenylpyridinium catalyzed by monoamine oxidase (Chapt. 4 and 9 in [50]). 

Cycloalkanes R R R H and chelating arenes ArH were oxidatively cross-conpled to Ar R R R by [RuClj(p-cymene)]2/TBHP/135°C (the reactants were the solvent) thus 2-phenylpyridine and cyclo-octane were cross-coupled cf. mech. Ch. 1. Other complexes (Ru(acac)3, [RuCl CCOD)] and RuHj(CO)(PPh3)3) also catalysed the reaction [78]. 

Af-methylmorpholine A-oxide or 4-phenylpyridine A-oxide as cocatalysts. The yields and enantioselectivities obtained with HgOg or urea hydrogen peroxide were comparable, with slightly better yields for the epoxidation with HgOg (73% versus 68% for the epoxide of 1,2-dihydronaphthalene in the presence of NH4OAC). 

A number of routes are available for the synthesis of 2,2 -bipyridines where one of the pyridine rings is built up from simpler entities. For example, condensation of 2-(aminomethyl)pyridine (31) with acetaldehyde or acetylene over a silicon-alumina catalyst at 450°C gives 2,2 -bipyridine, ° whereas 2-cyanopyridine reacts with acetylene at 120°C in the presence of a cobalt catalyst to afford 2,2 -bipyridine in 95% yield.2-Acetylpyridine with acrolein and ammonia gives 2,2 -bipyridine in the presence of dehydrating and dehydrogenating catalysts, and related condensations afford substituted 2,2 -bipyridines. ° In a similar vein, condensation of benzaldehyde with 2 mol of 2-acetylpyridine in the presence of ammonia at 250°C affords 2,6-di(2-pyridyl)-4-phenylpyridine, ° and related syntheses of substituted 2,2 6, 2"-terpyridines have been described. Likewise, formaldehyde with two moles of ethyl picolinoylacetate and ammonia, followed by oxidation of the product and hydrolysis and decarboxylation, affords a good... 

The chemistry of aryl groups attached to the 7r-deficient heterocycles is unexceptional and much as might be expected. Thus, electrophilic substitution of phenylpyridines occurs exclusively in the phenyl ring. 4-Phenylpyridine gives mononitration products in the ratio o m p, 20 33 47 (68JCS(B)862, 71JCS(B)712). The oxidation of phenylpyridines can lead to either a pyridinecarboxylic acid or benzoic acid. 

The 1,3-oxazepine (848) is thermally labile the main products are formylpyrroles but some 3-hydroxy-2-phenylpyridine is obtained (75TL1067). The benzoxazepines of type (849) are intermediates in the photochemical breakdown of quinoline iV-oxides and can sometimes be isolated. They normally break down to give 3-hydroxyquinolines (66TL2145, 67CPB663), but compound (849) can be converted by methylamine into the diaminoquinoline (850) (67TL5237). The benzoxazepinone (851) with sodamide forms a mixture of three isoquinoline... 

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