Oxopyridine

Reaction of 1,3-dicarbonyl compounds with IVJV-dimethylformamide dimethyl acetal followed by malonamide in the presence of sodium hydride gives 5,6-disubstituted 1,2-dihydro-2-oxopyridine-3-carboxamides, whereas reaction of the intermediate enamines with cyanothioacetamide or cyanoacetamide in the presence of piperidine provides 2-thioxopyridine-3-carboxamides and 4,5-disubstituted l,2-dihydro-2-oxopyridine-3-carboxamides, respectively <95S923>. P-Enaminonitriles 14 react with p-ketoesters and alkyl malonates, in the presence of stoichiometric amounts of tin(IV) chloride, to afford 4-aminopyiidines 15 and 4-amino-2-pyridones 16 <95T(51)12277>. 

The equilibrium between the amino and imino forms of cytosine has also been studied by Cieplak et al.9 Their results agree with those of Colominas et al. In this study, the related 2-oxopyridine and 2-oxopyrimidine molecules were also treated. In both these molecules the amine group of cytosine is not present, and in oxopyridine only one ring nitrogen is present. This enabled the keto-imino tautomerism to be studied in isolation. In both cases the imino form dominates in the gas phase, but the keto form is stabilised by solvation, and dominates in solution, in agreement with experiment. 

To a stirred suspension of N-(2,6-dimethyl-4-oxopyridin-l-yl)pyridin-ium tetrafluoborate (0.58 g, 2 mmol) in dry acetonitrile (20 ml) under nitrogen was added trimethyl phosphite (0.25 g, 2 mmol), followed by finely divided sodium iodide (0.30 g, 2 mmol). After 1 h at 25°C, the solvent was removed under reduced pressure, and water (20 ml) was added. The mixture was extracted with methylene chloride (3 x 15 ml), and the extracts were dried over magnesium sulfate, filtered, and evaporated under reduced pressure. The residue was dissolved in ethyl acetate (40 ml), heated at reflux for 4 h, evaporated under reduced pressure, and eluted on an alumina column (grade 1, neutral) with chloroform to yield pure dimethyl pyridin-4-ylphosphonate (0.36 g, 96%) of melting point (mp) 139 to 140°C. 

Bossio R, Marcos CF, Marcaccini S, Pepino R (1997) Studies on isocyanides and related compounds. A novel synthetic route to 1, 6-dihydro-6-oxopyridine-2-carboxylic acid derivatives. Heterocycles 45 1589-1592... 

Ethyl cyanoacetate reacts with 1,3-diketones to give 4,6-disubstituted 2-oxopyridine-3-carboxylates such as compound (483) (15JCS792), and with hydroxymethylenecyclohexanone to give a mixture of tetrahydroquinolines (484) and (485) (55AP174). 

These reactions were used to prepare complexes of 2-oxopyridines (39) to (41), 2-substituted phenyl derivatives (55-57) and others. One of the first oxopyridine complexes was prepared slightly differently (Scheme 20).170... 

There are no axial ligands in the 2-oxopyridine, 2-iminopyridine and 2-phenyl derivatives which have the shortest Cr—Cr bonds. The bromide ions in (58) are off-axis and beyond bonding distance. 

The /V-(2,6-dimethy 1-4-oxopyridin-1 -yl)pyridinium salts (15)24 have proved to be versatile intermediates for the regiospecific synthesis of 4-substituted pyridines (17) via attack by the appropriate carbon nucleophiles, e.g. ionized ketones,90 nitroalkanes,91 esters and nitriles,92 and a-diketones, a-keto esters, a-diesters, disulfones etc. (Scheme 10).93 Aromatization of the intermediate 1,4-dihydro adduct (16) was generally achieved under free radical conditions. 

These authors also show that irradiation by UV light strongly influences the tautomeric equilibria for oxopyridines as well as for thiopyridines and thiodiazines. More importantly, this provided a reliable method to determine the relative abundance of thiol and thione... 

The Ugi-4CR between cinnamaldehyde, benzoylformic acid, amines, and cyclohexyl isocyanide afforded the condensation products 103, which, under basic conditions, cyclized to the l,6-dihydro-6-oxopyridine-2-carboxamides 104 in high yields (Scheme 2.37) [68],... 

The decorporation of plutonium from mice by l,5-bis[l,2-dihydro-l-hydroxy-2-oxopyridin-6-yl)carbonyl]-l,5-diazapentane - results cited as manuscript in preparation 264) - has been reported. 

Dihydropyridin-4(lH)-on (= Methyl-1,2,3, 4-tetrahydro-4-oxopyridin-1-carboxylat) als Chromophor fur die photochemische [2 + 2]-Cycloaddition. Helvetica Chimica Acta, 74, 163-178. 

The pyridinium perchlorate (212), which is the precursor of the mesoionic oxazolone (213), is formed by the action of acetic anhydride and perchloric acid on l,2-dihydro-2-oxopyridin-l-acetic acid. The mesoion (213) is chemically unstable and is generated in solution for its reactions by treatment with a tertiary amine. Compound (213) is easily substituted at C-3, and with trifluoroacetic anhydride forms the stable 3-trifluoroacetyl mesoion (70JCS(C)1485). 

Other Ditungsten(II) Complexes. The 2-oxopyridine type ligand I, and related monoanionic ligand bridges such as 2-amino-6-methylpyridine and 2,4-dimethyl-6-hydroxy-pyrimidine have played an important role in the development of the chemistry of quad-... 

These new porphyrin compounds of Ru2+ are comparable to the previously known105) Ru2(C22H22N4)2, in which the bond length was found to be 2.379(1) A. There is only one other structurally characterized diruthenium(II,II) compound, namely, Ru2(mhp)4, where bridging by the 6-methyl-2-oxopyridine ligands occurs and the Ru-Ru distance is much shorter, 2.238(1) A106). 

Disposition in the Body. Readily absorbed after oral administration. Metabolised to A -methylnicotinamide, A-methyl-6-oxo-pyridine-3-carboxamide, iV-methyl-4-oxopyridine-3-carbox-amide, and by glycine conjugation to nicotinuric acid. It is rapidly excreted in the urine, and after administration of therapeutic doses about 34% is excreted unchanged in 6 hours. Nicotinic acid is a metabolite of nicergoline, nicotinamide, and nicotinyl tartrate. 

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