3-hydroxypyridine Derivatives Research Articles

Synthetic Photochemistry. IV. The Reaction of Betaines with Singlet Oxygen

Abstract Singlet oxygen was allowed to react with three 3-hydroxypyridine derivatives, I, II, and III, in order to investigate its general behavior toward dipolar substrates. The occurrence of an easy C=C cleavage process to give furanones (V and XI) through the dioxetones was a characteristic feature. In addition, maleimides (IV and IX), oxamates (VIII, XII and XIV), and a carbamate (XIII) were isolated as highly oxidized products.

Study of derivatives of 3-hydroxypyridine-1-oxide by the method of NMR-1H and13C spectroscopy

1. An analysis of the parameters of the NMR-13C and1H spectra of derivatives of 3-hydroxypyridine and their N-oxides showed that transition from the unoxidized base to the N-oxide is accompanied by a shift of practically all the signals into a higher-field region. 2. The NMR data were compared with a calculation of theπ-charges of derivatives of 3-hydroxypy-ridine-1-oxide in the anionic form. For 2-substituted 3-hydroxypyridine-1-oxides, a satisfactory correlation exists between the chemical shift and theπ-electron density.

Study of 3-hydroxypyridine derivatives by fourier spectroscopy method on13C nuclei

1. A. study was made of the spectra of some substituted 3-hydroxypyridines on the13C and1H nuclei. An estimate was made of the effect of alkyl, phenyl and benzyl groups on the chemical shifts of the carbon atoms of the β-pyridinol ring. 2. The spectrometric data were compared with a calculation of the π-charges and the experimentally observed order of substitution in the different positions of the β-pyridinol ring.

Vibrational spectra and structure of some 3-hydroxypyridine 1-oxide derivatives

The vibrational spectra of 3-hydroxypyridine 1-oxide and its derivatives were investigated.

Study of acid deuterium exchange in series of 3-hydroxypyridine derivatives

1. A study was made of the basic deuterium exchange of 3-hydroxypyridine and its alkyl derivatives. The constants for the rate of hydrogen exchange in the 2-, 6-, and 4-positions of the ring were determined, in which connection the 2-position of theβ-pyridinol ring proved to be the most reactive. 2. The introduction of methyl groups into the ring increases the rate of deuterium exchange in the 2- and 6-positions of theβ-pyridinol ring. 3. Deuterium exchange of the protons of the methyl groups of the substituents occurs under intense heating.

Study of basic deuterium exchange in the series of 3-hydroxypyridine derivatives

Study of basic deuterium exchange in the series of 3-hydroxypyridine derivatives

IR spectra and structure of 2-aryl-3-hydroxypyridines

The IR spectra of methyl, chloro, and phenyl derivatives of 3-hydroxypyridines in CCl4 solutions and in the crystalline state were studied. A comparison of the frequencies, half widths, and integral intensities of the bands of the stretching vibrations of the hydroxyl groups in the spectra of solutions of the 3-hydroxypyridine derivatives in CCl4 with the characteristic OH bands in the spectra of phenols demonstrates that 3-hydroxypyridines exist practically completely in the hydroxy form in dilute CCl4 solutions. The shift in the OH bands in the spectra of 2-phenyl-3-hydroxypyridine derivatives indicates that the OH group forms a π-hydrogen bond with the phenyl ring. The presence also of a band of a free OH group is evidence for the existence of s-cis and s-trans conformers relative to the C-O bond.

Influence of the pH of the medium on the chemical shifts of the PMR of 3- hydroxypyridine derivatives

1. The dependence of the chemical shift of the ring protons on the pH of the medium was studied by the PMR method for a number of derivatives of 3-hydroxypyridine. 2. A consideration of the family of dependences indicated the presence of three horizontal portions, corresponding to the ranges of acid, neutral, and alkaline media. 3. A comparison of the spectra of 2-methyl-3-hydroxypyridine and its N-methyl derivative confirms the presence of a bipolar structure in aqueous solution. 4. Good qualitative agreement was obtained between the estimated chemical shifts of the ring protons of derivatives of 3-hydroxypyridine in the bipolar form and theπ-electron densities calculated according to Hiickel method. 5. The transition from acid to alkaline medium produces a change in the sequence of arrangement of the proton signals at the 4- and 5-carbon atoms. 6. The presence of an intramolecular hydrogen bond in 2-dimethylaminomethyl-3-hydroxypyridine substantially influences the nature of the dependence of the chemical shift on the pH of the medium. 7. An analysis of the dependences of the chemical shift on the pH for an acid medium in the case of 2-dimethylaminomethyl-3-hydroxypyridine permits it to be concluded that separate protonation exists at the nitrogen of the ring and the nitrogen of the side chain.

Fluorescence studies on some hydroxypyridines including compounds of the vitamin B6 group.

1. The variations with pH (from 36n-sulphuric acid to 10n-sodium hydroxide) of the excitation and fluorescence wavelengths and fluorescence intensity of 2-, 3- and 4-hydroxypyridine and their O- and N-methyl derivatives were investigated. 2. 4-Hydroxy- and 4-methoxy-pyridine were non-fluorescent at all pH values. 3. The cations and dipolar ions of the 3-hydroxypyridine derivatives and the anion of 3-hydroxypyridine were fluorescent, but the neutral forms were not. 4. All the forms of the 2-hydroxypyridine derivatives were fluorescent. 5. Pyridoxol, pyridoxal and its 5-phosphate, pyridoxamine and pyridoxic acid and its lactone were studied similarly. All these compounds, except pyridoxal 5-phosphate, were more fluorescent than 3-hydroxypyridine. 6. The most fluorescent forms of these compounds are the anions, except for pyridoxol, where the dipolar ion was the most fluorescent form. The least fluorescent forms are the neutral molecules. The dipolar ions were appreciably fluorescent in all cases. 7. The most fluorescent form examined was the dianion of pyridoxic acid lactone. 8. The cations were all fluorescent except the cations of 2- and 3-methoxypyridine. All the cations showed excited-state ionization. The excited pK(a) values of these cations were determined and the results are discussed with reference to Weller's (1952) equation relating ground- and excited-state dissociation constants. 9. The pK(a) values for all ionizations undergone by the compounds examined were determined from fluorescence data. 10. Stokes shifts for the various ionic and neutral species of the compounds examined were calculated and are discussed.

Synthesis of nitrogen-containing heterocyclic compounds. CIII. Synthesis of 3-hydroxypyridine derivatives

Synthesis of nitrogen-containing heterocyclic compounds. CIII. Synthesis of 3-hydroxypyridine derivatives

Spectra and Ionization Constants of the Vitamin B6 Group and Related 3-Hydroxypyridine Derivatives1

Spectra and Ionization Constants of the Vitamin B₆ Group and Related 3-Hydroxypyridine Derivatives¹