Pyrid-4-ones, methylation

CYAN 0-6-METHYL-2(l)-PYRID ONE (Nicotinonitrile, l,2-dihydro-6-methyl-2-oxo-)... 

The foregoing conclusions are further supported by a refined X-ray analysis of pyrid-2-one, which indicated that the mobile hydrogen atom is attached to the nitrogen atom in the solid state and that individual molecules are bound into helices by N—H- -0 hydrogen bonds. An oxo structure is also indicated by the molar refractivity of pyrid-2-one. The dipole moment of 4-methoxypyridine is ca. 3.0 debyes in dioxane, whereas the values for pyrid-4-one and its 1-methyl derivative are much higher, ca. 6.0 debyes indicating the... 

Between 1951 and 1953 investigations by three English groups clearly demonstrated the preponderance of the oxo forms of pyrimidin-2- and -4-ones by comparing the ultraviolet spectra of these compounds with those of the N and 0-alkylated derivatives, The o-quinonoid form 91 (R = H) is favored by the evidence that A -methylation of the 6-methyl derivative of 89a does not cause a bathochromic shift in the ultraviolet spectrum (A -methylation of pyrid-4-one causes a bathochromic shift, but this is not observed for pyrid-2-one) The isomeric A -methyl derivatives of pyrimidin-4-ones [e.g., 91 (R = Me) and 90 (R = Me)] form similar cations (e.g., 92 and 93), and hence the equilibrium constant between... 

A mixture of 1- and 2-alkylated products was obtained from reaction of 5-methylpyrazolo[4,3-b]pyridine with methyl iodide in ethanolic sodium hydroxide.111 Methylation of reduced pyrazolo[4,3-c]pyrid-3-ones gave either 1- or 3a-substituted products (Scheme 3).149... 

Hydroxy-[l,2,4]triazolo[4,3-fl]pyridine (91) was reluctant to react with the common hydroxylic chlorinating agents, giving at best, the 3-chloro compound in only 15% yield with pWphorus oxychloride-dimethylaniline. Methylation of (91) produced 2-methyl-[l,2,4]triazolo[4,3-n]pyrid-3-one (92) whereas methylation of the 3-thiol (93) resulted in methyl [l,2,4]triazolo[4,3-a]pyrid-3-yl sulfide (94), a molecule also resistant to nucleophilic substitution (66JOC265). Potassium ferricyanide oxidation of (93) resulted in the corresponding disulfide. 

Reaction of arylhydrazones 216 of piperidin-2-ones with methyl chloro-formate, phosgene, or thiophosgene yielded (80USP4213773) the fused-ring system 217. Reaction of 2,2 -azopyridine (218) with diazoalkanes afforded [66JCS(C)78 73LA2088] the 2-(pyrid-2-yl)-l,2,4-triazolo[4,3-a]-... 

Brown, S. M. Bowden, M. C. Parsons, T. J. McNeilly, P. de Fraine, P. J., 6-(Trifluoro-methyl)pyrid-2-one Development and Scale-Up of a Ring Synthesis Route Based on Trifluoro-acetic Anhydride. Org. Process Res. Dev. 1997, 1,370. 

Photolysis of benzene solutions of l-methoxycarbonyl-2-naphthylmethyl 2,6-di-methyl substituted phenyl ethers induces C-O cleavage with formation of 2,4-cyclohexadienone intermediates which are subsequently photo-rearranged into meta substituted phenols. In methanol, 9-anthrylmethoxy-pyrid-2-one or l-pyrenylmethoxypyrid-2-one undergo photoheterolysis to give the C-O heterolysis products l-hydroxypyrid-2-one and the arylmethyl methyl ether, together with 2-pyridone, aryl-substituted methanol and aryl aldehyde derived from homolysis of the N-O bond. Evidence shows that an intramolecular exciplex plays a crucial role in C-O bond heterolysis. 

A soln. of fl / j /ro-5-acetyl-4-hydroxy-3-methyl-2-(2-(propargyloxy)phenyl)thiazo-lium hydroxide in toluene heated with stirring under reflux for 12h - 3-acetyl-l-methyl-5i/-benzo[/i]pyrano[4,3-/i]-17/-pyrid-2-one. Y 77%. F.e. and 2(l )-pyrimidi-none ring (with a nitrile group as dipolarophile) s. K.T. Potts et al., J. Org. Chem. 54, 1077-88 (1989). 

Methyl 2-acetyl-3-indolylacetate dissolved in methanolic NHg (d. 0.78) in a closed flask, and stored 2 weeks 2-methyl-indolo-2, 3 3,4-pyrid-6-one. Y 80%. 

In the presence of sulfur compounds (e.g. cysteine) pentoses and methylpentoses produce, in addition to 4-hydroxy-5-methyl-2H-furan-3-one and 4-hydroxy-2,5-dimethyl-2ff-furan-3-one, respectively, related compounds containing sulfur in the molecule. Many of these compounds resemble the aroma of cooked or roasted meat. In the presence of primary amines, 1-deoxyhexo-2,3-diuloses derived from disaccharides yield pyridinium betaines and, further, pyrid-4-ones and isomeric 2-acetylpyrroles. The reaction with secondary amines leads to N-substituted... 

Recently, many investigators have extended the early observations that the ultraviolet spectra of - and y-hydroxypyridines resemble those of their A -methyl (not the 0-methyl) derivatives. This spectral resemblance is found both in aqueous solutions and in solutions of solvents with low dielectric constants, e.g., quinol-4-one in benzene, indicating that these compounds exist predominantly in the oxo form under all conditions. These data are summarized in Table I. In contrast, 4-hydroxyquinoline-3-carboxylic acid has been tentatively concluded to exist in the hydroxy form pyrid-2-one-4-carboxylic acid has also been formulated as a hydroxy compoimd, but this has been disputed. ... 

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