2- Methyl-5-substituted-pyridines, formation

Four 2-substituted pyridines were found to give the expected 6,6 -disubstituted 2,2 -bipyridines in yields corresponding to only about 3% of the amount of 2,2 -bipyridine formed from pyridine itself under comparable conditions. It is also of interest that with three 2-methyl-pyridines the expected 6,6 -dimethyl-2,2 -bipyridines were accompanied by smaller amounts of 2,2 -bipyridines having no methyl groups in the 6,6 -positions. Moreover, a very small amount of 5,5 -dimethyl-2,2 -bipyridine (8) was isolated following reaction with 2,5-lutidine (6) but no 3,3 -dimethyl-2,2 -bipyridine could be detected. The absence of this compound suggests that 3,3, 6,6 -tetramethyl-2,2 -bipyri-dine (9) is not an intermediate, but that the 2-methyl group is lost before the formation of the 2,2 -bipyridine (6—>8). 

Most of the reactions with quinolines and degassed Raney nickels have been carried out at the atmospheric boiling point (above 230 C), a condition which is known to favor the formation of by-products. With quinoline and 4-methylquinoline (lepidine), however, the yields of the 2,2 -biquinolines were increased three to four times by heating in vacuo at 150° C, and it seems probable that other quinolines will behave similarly. Table II also shows that the yields of 2,2 -biquino-lines obtained under comparable conditions vary with the position of the methyl group in a fashion reminiscent of the trends observed with the pyridines (Table I). This similarity extends to the behavior of the two 2-methyl substituted quinolines studied, which undergo loss of the 2-methyl group to some extent and form traces of 2,2 -biquinolines. 

Ni-Co ferrites with the general formula Nii cCoxFe204 were tested for the methylation of pyridine [110]. It was observed that the systems possessing x values >0.5 are selective for 3-picoline formation, whereas the ones with x values 0 and 0.2 give a mixture of 2- and 3-picolines. Pyridine conversion increased with the progressive substitution of Ni ions by Co ions. The cation distribution in the spinel lattice influences their acidic and basic properties, and these factors have been considered as helpful to evaluate the activity of the systems. 

Reactions with methylphenylcyclopropenone (154) provided an opportunity to compare the reactivities of the two different C—CO bonds. The reaction of 2-aminopyridines with methylphenylcyclopropenone (154) proceeded more slowly than with the diphenyl analog (153). In ether, formation of the ds-2-oxopyrido[l,2-a]pyrimidines (158 R1 = Me) and/or the imidazo[l,2-c<]pyridines (162) was observed, indicating that the cycloaddition proceeds via cleavage of the PhC—CO bond. The methyl-substituted trans-2-oxopyrido[l,2-a]pyrimidine (160 R1 = Me) was only detected in the reaction mixture of 2-amino-3-methylpyridine, where the H NMR spectrum exhibited signals assigned to 160 (R1 = Me, R = 9-Me). The compound was not isolated. The imidazo[l,2-a]pyridines (162) readily hydrolyzed to the acids (163), work-up therefore leading mainly to isolation of the acids. 

Another effect is obvious from experiments with a Al/Fe ratio of 400 as soon as all the aluminum centers carry one longer hydrocarbon chain, further ethene polymerization proceeds only sluggishly. This indicates the formation of an active catalyst complex between MAO - methyl-substituted aluminoxane - and diimine pyridine iron with the formed larger alkyl-substituted aluminoxane, such an associate between catalyst and co-catalyst cannot form so readily or is less accessible and the activity is much lower. 

As shown recently , refluxing 6-methyl-substituted 3-azapyrylium perchlorates 377 in DMF/AcjO mixture gives the pyrido[l,2-c]pyrimidinium salts 379, while when carrying out this reaction at 20 C it gives the -acylaminovinyl pyridines 380. The authors assume that formation of anhydro base 378 takes place initially, and then 378 reacts with another molecule of 377 . The same products 379 and 3 were isolated from the condensation of 6-methylene-1,3-oxazines 378 with 3-azapyrylium salts 377 prepared beforehand (equation 108). The structure of 379 (R = Et) was established by X-ray crystallography. 

Ultraviolet irradiation of pyridines can prodnce highly strained species that can lead to isomerised pyridines or can be trapped. The three picolines and the three cyano-substituted pyridines constitute photochemical triads irradiation of any isomer, in the vaponr phase at 254 nm, results in the formation of all three isomers. From pyridines and from 2-pyridones 2-azabicyclo[2.2.0]-hexadienes and -hexenones can be obtained in the case of pyridines these are nsnally nnstable and revert thermally to the aromatic heterocycle. Pyridone-derived bicycles are relatively stable, 4-alkoxy- and -acyloxy-pyridones are converted in particnlarly good yields. Irradiation of iV-methyl-2-pyridone in aqueous solution prodnces a mixture of regio- and stereoisomeric 4n pins 4n photo-dimers. ... 

In unsubstituted pyridine ligand the selectivity for the formation of 2-cyclohexenone was almost 100 %. Substitution of methyl groups in the beta and gamma positions of the pyridine ring decreases the selectivity for formation of 2-cyclohexenone and increases that of 2-cyclohexen-l-ol. Product yield also increases with methyl substitution in tbe pyridine ring. The oxidation reaction did not occur in protic solvents like methanol or in mixtures of solvent like chloroform or benzene. Product yield was very low compared to CHP as the oxidising agent (Table-3). In all these reactions with NMO, cyclohexene oxide was not detected. Chloroform was found to be the suitable solvent for tbe reaction. 

The presence of pyridine compounds in smoke is naturally associated with the tobacco alkaloids. The formation of substituted pyridines that occur during the pyrolysis of nicotine has long been known [Woodward et al. (4275a), Kaburaki et al. (2006), Jarboe and Rosene (1923a), Schmeltz et al. (3499)]. Pyridine, 3-methyl- and/or 4-methylpyridine,... 

Polyester fibers are composed of linear chains of polyethylene terephthalate (PET), which produces benzene, benzoic acid, biphenyl, and vinyl terephthalate on pyrolysis. Acrylic fibers comprise chains made up of acrylonitrile units, usually copolymerized with less than 15% by weight of other monomers, e.g., methyl acrylate, methyl methacrylate, or vinylpyrrolidone. Thermolysis results in the formation of acrylonitrile monomer, dimers, and trimers with a small amount of the copolymer or its pyrolysis product. In this case, the acrylic is Orion 28, which contains methyl vinyl pyridine as comonomer. Residual dimethyl formamide solvent from the manufacturing process is also found in the pyrolysis products. Cotton, which is almost pure cellulose, comprises chains of glucose units. The pyrolysis products of cellulose, identified by GC/MS, include carbonyl compounds, acids, methyl esters, furans, pyrans, anhydrosugars, and hydrocarbons. The major pyrolysis products are levoglucosan (1,6-anhydro-B-D-glucopyranose) and substituted furans. 

The nickel-catalysed 2 + 2 + 2-cycloaddition of a 3-methyl-2-pyridyl aldimines with alkynes produced 1,2-dihydropyridine adducts in good yields. A key step in this transformation is the formation of aza-nickelacycle intermediates. The iron-catalysed 2 + 2 + 2-cycloadditions of alkyne nitriles with alkynes, in the presence of pyridyl bisimine ligands (95), formed substituted pyridines in good yields. The nickel-catalysed 2 + 2 + 2-cycloadditions of diynes and cyanamides have been investigated. The reactions have been shown to be regioselective, and cycloadducts are produced in good to excellent yields. ... 

As noted earlier, the replacement of halogen by an amino group (a substitution reaction at carbon and at nitrogen [ ]) is generally not useful for the preparation of primary (RNH2) or secondary (R2NH) amines since the alkylamines are stronger bases than ammonia. However, the substitution reaction is useful for tertiary (R3N) amines, for example, the A-methylation of pyridine with methyl iodide (Equation 10.48) and the formation of other quaternary ammonium salts (cf. the Menschutkin reaction. Table 7.7, item h). 

---