2-Hydroxy-6-methoxy-pyridines

Next, the substituent effect on the tautomeric preference should be considered. For example, ortho-derivatives of pyridine with substituents which have an acidic proton may participate in prototropic tautomerism (Scheme 12 2002A(11)198). Stabihty of the particular tautomeric form depends on an additional substituent and intermolecular H-bonding (Scheme 13). Moreover, tautomeric preferences can be changed by a solvent. For 6-X substituted 2-hydroxypyridines, the tautomeric equihbrium is stron y affected by substituents which can change the Tt-electron structure of fragments involved in the prototropy. For example, it was found that 2-hydroxy-6-chloro-and 2-hydroxy-6-methoxy-pyridines exist mainly in the aromatic form a... 

The 2-nitration of 3-hydroxy- and 3-methoxy-pyridine in 85-96% sulphuric acid involves the conjugate acids, whilst the 3-nitration of 6-hydroxy and 6-methoxy-2-pyridone in 70-77 % sulphuric acid involves the free bases, which react at, or near to the encounter rate. ... 

In their acidity, basicity, and the directive influence exerted on electrophilic substitution reactions in benzenoid nuclei, acylamino groups show properties which are intermediate between those of free amino and hydroxyl groups, and, therefore, it is at first surprising to find that the tautomeric behavior of acylaminopyridines closely resembles that of the aminopyridines instead of being intermediate between that of the amino- and hydroxy-pyridines. The basicities of the acylaminopyridines are, indeed, closer to those of the methoxy-pyridines than to those of the aminopyridines, the position of the tautomeric equilibrium being determined by the fact that the acyl-iminopyridones are strong bases like the iminopyridones and unlike the pyridones themselves. Thus, relative to the conversion of an... 

Kinetic parameters k, often also and AS, occasionally AV ) for formation and dissociation of several pentacyanoferrate(II) complexes [Fe(CN)5L]" have been established. Ligands L include several S- and A-donor heterocycles,4-methyl- and 4-amino-pyridines, a series of alkylamines, 3- and 4-hydroxy- and 3- and 4-methoxy-pyridines, several amino acids, nicotinamide, " 4-pyridine aldoxime, 3-Me and 3-Ph sydnones, several bis-pyridine ligands,neutral, protonated, and methylated 4,4 -bipyridyl, 1,2-bis(4-pyridyl)ethane and traTO-l,2-bis0-pyridyl)ethene, pyrazine- 4,4 -bipyridyl- and bis(4-pyridyl)ethyne-pentaammine-cobalt(III), edta-ruthenium(III), and pentaammineruthenium-(II)and-(III) complexes of... 

The 4-pyridones behave similarly, with the neutral tautomer reacting below pH 6 and the anion at higher pH. The observation that 4-methoxy-pyridine shows little comparative reactivity over the whole range is evidence that the hydroxy tautomer is not involved in the bromination process. Again, once the first bromine has entered the ring, further bromination occurs more readily because of easier anion formation (83CJC2556). 

The reaction of trans-dimethoxy tellurium tetrafluoride with pyridine produced pyridinium /ra .v-(methoxy)oxo(tetrafluoro)tell urate (VI). The tetramethylammonium salt was obtained, when trans-dimethoxy tellurium tetrafluoride was reacted with trimethylamine in dichloromethane2. Treatment of these salts with 96% sulfuric acid gave trans-hydroxy methoxy tellurium tetrafluoride. ... 

Methoxy-pyridin laBt sich iiber Raney-Nickel bei 1507150 bar zu3-Methoxy-pi-peridin umsetzen5, sein 2-(2-Hydroxy-propyl)-Derivat wird iiber Platin(IV)-oxid in Essigsaure (7072-3 bar) zu 74% d.Th. zum 3-Methoxy-2-(2-hydroxy-propyl)-piperidin hydriert6. Einige 3-Methoxy-4-pyridone werden mit Raney-Nickel bei 15 57110 bar zu den 4-Hydroxy-3 -methoxy -piperidinen hydriert7. 

Reactions of carbonyl compounds with hydroxy-, methoxy, and benzyloxyamines are usually conducted in pyridine solution. To speed up the reaction the reaction mixture is heated at 60-100°C. The solvent (pyridine) is removed by evaporation in a flow of nitrogen, the sample is dissolved in ethyl acetate and an aliquot of the solution obtained is analysed by GC. 

Pyridin-2-one, 1-hydroxy-fluorescence spectrum, 2, 163 (81XL1515) Pyridin-2-one, 6-methoxy-pK 2, 151 <71JCS(B)289)... 

A number of heteroaromatic monothiocarboxylic acids are formed by Pseudomonas sp. From P. putida, there was isolated pyridine-2,6-di-(mon-othiocarboxylic acid) 46 (Scheme 16). Of interest is the fact that in P. stutzeri KC, a copper complex of 46 is the active agent for a one electron transfer in the bacterial biodegradation of CCI4. Methylation of P. putida extracts provides a number of related structures such as 47. In addition, a P. fluorescens sp. contains 8-hydroxy-4-methoxy-quinoline-2-monothiocarboxylic acid 48.98... 

Citral reacted in pyridine with 2-hydroxy-3-methylcarbazole and with 2-hydroxy-7-methoxy-3-methylcarbazole to give ethers 144 (R = H and... 

Streptonegrin (negrin, 5-amino-6-[7-amino-5,8-dihydro-6-methoxy-5,8-dioxo-2-quinolinyl]-4-[2-hydroxy-3,4-dimethoxyphenyl]-3-methyl-2-pyridinecarboxylic acid) [3930-19-6] M 506.5, m 262-263°, 275°(dec). Purified by TLC on pH 7-buffered silica gel (made from a slurry of Silica Gel 60 and 4(X)ml of 0.05M phosphate buffer pH 7.0) and eluted with 5% MeOH/CHClj. The extracted band can then be recrystd from Me2CO or dioxane as almost black plates or needles. It is soluble in pyridine, Me2NCHO, aqueous NaHCOy (some dec), and slightly soluble in MeOH, EtOH, EtOAc and H2O. It has a pKa value in the range 6.2-6.4 (dioxane/H2O 1 1) and UV 248, 375-380nm (e 38400 and 17400). [Weinreb et al. JACS 104 536 1982 Rao et al. JACS 85 2532 1963]. It is an antineoplastic and causes severe bone marrow depression [Wilson et al. Antibiot Chemother 11 147 7967]. 

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