Pyridines alkyl-, various

One of the best known examples of polymer-transformation reactions is the quaternization of poly(4-vinyl pyridine) by various alkyl... 

Alkyl radicals for such reactions are available from many sources such as acyl peroxides, alkyl hydroperoxides, particularly by the oxidative decarboxylation of carboxylic acids using peroxy-disulfate catalyzed by silver. Pyridine and various substituted pyridines have been alkylated in the 2-position in high yield by these methods. Quinoline similarly reacts in the 2-, isoquinoline in the 1-, and acridine in the 9-position. Pyrazine and quinoxaline also give high yields of 2-substituted alkyl derivatives <74AHC(16)123). 

Quantum yields of formation of OaC Ag) obtained by irradiation of benzene solutions of various flavonoids, and by irradiation of oxodiperoxo-molybde-num(VI) complexes of the type (L-L)MoO(02>2 (L-L = 2-(l-alkyl-3-pyrazolyl)-pyridine, alkyl = Bu, n-octyl, n-octadecyl L-L = 2-(3-n-octyl-2-... 

The IR-spectra of 41 tobacco alkaloids and related compounds have been tabulated (S5). Nornicotine, nicotine, myosmine, nicotyrine, anabasine, anatabine, and dihydronicotyrine were separated from an extract of tobacco alkaloids by countercurrent partition (86). Thin-layer chromatography has been used to separate nicotine, nornicotine, anabasine, and nicotyrine (57). The use of gas chromatography to separate tobacco alkaloids has been studied. The retention times of 11 tobacco alkaloids on polyethylene glycol columns has been reported (88) and the effect of the column packing on the retention times of pyridine bases has been described (89). Mixtures containing pyrrolidine, piperidine, pyridine, and various alkylated pyridines have been separated using programed temperature control (90). 

Buriak and co-workers chose a different modification strategy to Crabtree s catalysts and they replaced the pyridine with various alkyl phosphines. Optimization studies revealed that complex [(IMes)Ir(COD)(PBu3)]BARF 5 (BARF = tetrakis[3,5-bis(triflouromethylphenyl)borate]) was the most stable and displayed similar activity to 3. Furthermore, 5 was active for highly hindered tri- and tetrasubstituted alkenes at 1 atm pressure of H2 in the presence of air. 

The stability constants for the coordination of pyridine or substituted pyridines to various alkylcobalt porphyrin systems have been reported. This study has been done in order to observe the m-influence of hydroporphyrin macrocycles on axial position and alkyl exchange reactions. The alkyl exchange reactions of organocobalt(lll) porphyrins with a cobalt(ll) complex of a distinguishable porphyrin or tetrapyrrolc have been studied. The equilibrium constants for the alkyl transfer have been reported. The exchange of the axial ligand is reversible and it follows a bimolecular mechanism. Thermodynamic and activation parameters for homolytic Co-C bond dissociation have been obtained on the (TAP)CoC(CH3)2CN complex (TAP = tetraanisylporphirinato). ... 

Metal Cleaning. About 204 thousand metric tons of HCl (100% basis) was consumed in 1993 for steel pickling, wherein the hydrochloric acid readily dissolves all of the various oxides present in the scale formed during the hot rolling process. Using suitable inhibitors such as alkyl pyridines, HCl reacts very slowly with the base metal rendering the surface so clean that it must be passivated with a mild alkaline rinse. 

By-Products. Almost all commercial manufacture of pyridine compounds involves the concomitant manufacture of various side products. Liquid- and vapor-phase synthesis of pyridines from ammonia and aldehydes or ketones produces pyridine or an alkylated pyridine as a primary product, as well as isomeric aLkylpyridines and higher substituted aLkylpyridines, along with their isomers. Furthermore, self-condensation of aldehydes and ketones can produce substituted ben2enes. Condensation of ammonia with the aldehydes can produce certain alkyl or unsaturated nitrile side products. Lasdy, self-condensation of the aldehydes and ketones, perhaps with reduction, can lead to alkanes and alkenes. 

Various alkyl-substituted pyridine derivatives are formed from the condensation of butyraldehyde with ammonia at high temperatures. For example, cocondensation of //-butyraldehyde with acroleia [107-02-8] and ammonia at 400°C over a borosiUcate 2eohte gives 3-ethylpyridine [536-78-7] ia 70% yield... 

Various sources of fluoride ion have been investigated, of which highly nucleophilic tetraalkylammonium fluorides ate the most effective Thuf, fluoro alkyl halides and N (fluoroalkyl)amines are efficiently synthesized by treatment of the corresponding trifluoromethanesulfonic esters with tetrabutylammonium fluoride trihydrate in aprotic solvents [5fl] (equation 34) The displacement reactions proceed quantitatively at room temperature within seconds, but tail with hydrogen fluoride-pyridine and give reasonable yields only with hydrogen fluo ride-alkylamine reagents... 

Few other reactions of series of substituted pyridines have been investigated extensively. Dondoni, Modena, and Todesco have measured the rate of N-oxidation of a limited series of pyridines and found a good correlation with normal u-values with a p-value of — 2.23. The A-alkylation of pyridines with alkyl iodides in nitrobenzene has been studied by Brown and Cahn and by Clarke and Rothwell. Unfortunately, the only data available are for the parent compound and for alkyl derivatives, and, since the a-values for the various alkyl groups in a given position are substantially constant, this leaves a correlation of only three independent points. However, the rates of A-alkylation of the j8- and y-alkyl derivatives are so nearly equal that it appears as if no correlation existed. Clarke and Rothwell have also studied the alkylation with allyl bromide in nitromethane at various temperatures, and in this case a more extensive series is available. The authors state that no overall Hammett correlation is obtained however, the j8-substituted derivatives fall on one straight line and the y-derivatives on another one with a different slope. The data are shown in Fig. 2. The line for the j8-compounds, p = — 2.53 0.31, r = 0.95, is seen not to be very good the line for the y-derivatives, p = — 1.42 0.06, r = 0.99, is much more satisfactory. It does not seem likely that the discrepancy is due to the intervention of resonance effects, since in this case one would expect the correlation for the y-derivatives to be poorer than that for the j8-analogs. More extensive studies with a wider variety of substituents would seem very desirable. 

Abbreviations acac, acetylacetonate Aik, alkyl AN, acetonitrile bpy, 2,2 -bipyridine Bu, butyl cod, 1,5- or 1,4-cyclooctadiene coe, cyclooctene cot, cyclooctatetraene Cp, cyclopentadienyl Cp, pentamethylcyclopenladienyl Cy, cyclohexyl dme, 1,2-dimethoxyethane dpe, bis(diphenyl-phosphino)ethane dppen, cis-l,2-bis(di[Atenylphosphino)ethylene dppm, bis(diphenylphosphino) methane dppp, l,3-bis(diphenylphosphino)propane eda,ethylenediamine Et,ethyl Hal,halide Hpz, pyrazole HPz, variously substituted pyrazoles Hpz, 3,5-dimethylpyrazole Me, methyl Mes, mesityl nbd, notboma-2,5-diene OBor, (lS)-endo-(-)-bomoxy Ph, phenyl phen, LlO-phenanthroline Pr, f opyl py, pyridine pz, pyrazolate Pz, variously substituted pyrazolates pz, 3,5-dimethylpyrazolate solv, solvent tfb, tetrafluorobenzo(5,6]bicyclo(2.2.2]octa-2,5,7-triene (tetrafluorobenzobanelene) THE, tetrahydrofuran tht, tetrahydrothicphene Tol, tolyl. 

Brown and McDonald (1966) provided another type of kinetic evidence for these size relationships by determining secondary kinetic isotope effects in reactions of pyridine-4-pyridines with alkyl iodides. For example, the isotopic rate ratio in the reaction between 4-(methyl-d3)-pyridine and methyl iodide at 25-0 C in nitrobenzene solution was determined to be kjyfk = l-OOl, while that in the corresponding reaction with 2,6-(dimethyl-d6)-pyridine was 1-095. (Brown and McDonald (1966) estimate an uncertainty of 1% in the k jk values.) Furthermore, the isotopic rate ratio in the case of the 2-(methyl-d3)-compound increased from 1 030 to 1-073 as the alkyl group in the alkyl iodide was changed from methyl to isopropyl, i.e. the isotope effect increased with increasing steric requirements of the alkyl iodide. 

Chiral pyridine-based ligands were, among various Ar,AT-coordinating ligands, more efficient associated to palladium for asymmetric nucleophilic allylic substitution. Asymmetric molybdenum-catalyzed alkylations, especially of non-symmetric allylic derivatives as substrates, have been very efficiently performed with bis(pyridylamide) ligands. 

In the 1988-1999 period, almost all absolute kinetic studies of carbenic reactions employed LFP with UV detection. Carbenes that contain a UV chromophore (e.g., PhCCl) are easily observed, and their decay kinetics during reaction can be readily followed by LFP.11 However, alkyl, alkylhalo, and alkylacyloxycarbenes are generally transparent in the most useful UV region. To follow their kinetics, Jackson et al. made use of the ylide method, 12 in which the laser-generated carbene (2) is competitively captured by (e.g.) pyridine, forming a chromophoric ylide (3, cf. Scheme 1). The observed pseudo first order rate constants (kobs) for the growth of ylide 3 at various concentrations of pyridine are monitored by UV spectroscopy, and obey Eq. 1. 

In marked contrast to the above results, double nitrile insertion into both the titanium-alkyl and titanium—vinyl bonds occurs to form the diazatitanacycles 74. Treatment of these titanacycles with dry hydrogen chloride affords the tetrasubstituted pyridine derivatives 75 (Scheme 14.32) [74], On the other hand, 2,3-diphenyltitanacyclobutene reacts with various nitriles to afford the products of mono-insertion, which afford the corresponding unsaturated ketones upon hydrolysis [73,74]. 

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