Investigation of the reaction of vinyloxy-pyridines and n-vinylpyridines with bromine

The addition of bromine to vinyl derivatives of 2-hydroxypyridine, 2-hydroxylepidine, and 8-hydroxyquinoline was studied. The behavior of the compounds differs as a function of the structure and the position of the vinyl group attached to the oxygen or nitrogen of the pyridine ring. A complex involving the unshared electron pair of the nitrogen atom is obtained with 2-vinyloxypyridine and bromine. N-Vinyl-2-pyridone and 2-vinyloxylepidine add bromine primarily at the double bond of the vinyl group. This reaction proceeds in a more complex fashion with N-vinyl-2-lepidone and 8-vinyloxyquinoline. The structures of the synthesized compounds were investigated by means of IR and PMR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 626–630, May, 1971.     

Polarogmphic study of azo derivatives of 3-hydroxypyridine

It was established that in most cases azo derivatives of 3-hydroxypyridine are reduced successively in two one-electron steps at more positive potentials than azobenzene on a dropping mercury electrode in anhydrous dimethylformamide (DMF) with a 0.05 N solution of tetraethylammonium perchlorate as the base electrolyte. However, one two-electron wave was observed for some compounds; this is evidently associated with self-protonation owing to the presence of the appropriate substituents. Some 3-hydroxypyridine derivatives exist in DMF in various tautomeric forms, as a result of which additional reduction waves appear. More pronounced reduction with respect to the azo group is observed only for three of the investigated compounds.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1240–1244, September, 1981.     

A new,one-step transformation of furoic acid derivatives to 2-Amino-3-hydroxypyridines

2-Arnino-3-hydroxypyridine and its 6-methyl derivative can be prepared in yields up to 55% by heating 2-furoic acid derivatives at 200-250° with ammonia in the presence of an acidic catalyst. The reaction is preferably conducted in an amide or a nitrile as solvent.     

Reactivity of heterocyclic compounds in nitration. 8. Nitration of 3-hydroxypyridine and its substituted forms

Nitration of 3-hydroxypyridine and its substituted forms has been studied under various conditions. It is shown that, depending on the reaction temperature and the nitrating agent, the end products of the synthesis can be 3-hydroxy-2,6-dinitropyridine or 3-hydroxy-2,4,6-trinitropyridine. The possibility of substitutional nitration of iodine derivatives of 2- and 3-hydroxypyridine is demonstrated.For Communication 7, see [1].Kazan' State Technological University, Kazan' 420015, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 958–961, July, 1998.     

Condensation de la base de mannich de l'hydroxy-3 pyridine avec les ethers vinyliques: Accés aux alcoxy-2 aza-5 chromannes

The Mannich base of 3-hydroxypyridine can be thermally condensed with vinyl ethers to yield 2-alkoxy-5-azachromans. The condensation with α-pyran affords the cis isomer of 5,6,7,8,8a,10a-hexahydro-5-oxa-1-azaxanthene.     

Intramolecular aminolysis of trichloroethyl esters: a mild macrocyclization protocol for the preparation of cryptophycin derivatives

The bifunctional catalyst 2-hydroxypyridine (2-pyridone) is shown to promote the intramolecular aminolysis of the polyfunctionalized long-chain amino trichloroethyl ester 8 to afford cryptophycin-51 (4). This process for the construction of the macrocyclic core of cryptophycin derivatives is noteworthy for its convenience, avoidance of expensive coupling reagents, and use of mild reaction conditions.     

The electronic structures of 3-hydroxypyridines.

Chemical shifts are reported for 3-hydroxypyridine derivatives in acid, neutral, and alkaline media. The -charge distribution is reported (LCAO method, Huckel's approximation) for the neutral, anionic, cationic, and bipolar species. The results reveal the trends in the electron-density distribution in 3-hydroxypyridine derivatives.     

Convenient synthesis of 5-azacoumarins

2-Formyl-3-hydroxypyridine and its 6-methyl derivative have been condensed with ethoxycarbonylmethyl-enetriphenylphosphorane and alkyl derivatives to afford 5-azacoumarins substituted in the second case by an alkyl group at 3-position by two different ways according to the used phosphorane.     

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 -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.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 187–190, February, 1972.     

Studies in the heterocyclic series. XV. Synthesis and reactions of the first triazaphenoxazine ring system

1,4,9-Benzo[b]triazaphenoxazine, the first and parent compound of this new heterocyclic ring, as well as its derivatives were prepared essentially by cyclo-condensation of 2-amino-3-hydroxypyridine with the appropriate 2,3-dichloroquinoxaline in the presence of alkaline DMF or DMAC. Nitration of the product with mixed nitric and sulfuric acids gave the corresponding 13-nitro derivative. Structural assignments were made by chemical evidence and by a study of the ultraviolet, infrared, nmr and mass spectra.     

Tautomerism of phenylazo derivatives of 3-hydroxypyridine and their N-oxides

Azophenol-quinone hydrazone tautomerism was detected for phenylazo derivatives of 3-hydroxypyridines and their N-oxides. The absorption maxima of the phenylazo derivatives of 3-hydroxypyridine have a greater (than their N-oxides) tendency to be shifted to the longer-wavelength region.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 810–812, June, 1973     

Synthesis of 3-Hydroxy-6-Methyl- and 3-Hydroxy-2-(2-phenylethyl)pyridines and Their Sulfur-Containing Amino and Hydroxymethyl Derivatives

The aminomethylation of 3-hydroxy-6-methyl- and 3-hydroxy-2-(2-phenylethyl)pyridines by secondary amines has been investigated. It was shown that like 2-alkyl-3-hydroxypyridine aminomethylation is directed primarily to position 6 and then 4 of the pyridine ring. On heating the aminomethyl derivatives of 3-hydroxy-6-methyl- and 3-hydroxy-2-(2-phenylethyl)pyridines with acetic anhydride the corresponding acetoxy derivatives were obtained, which were converted on heating with hydrochloric or hydrobromic acids into hydroxy and bromomethyl derivatives. Isothioureidomethyl and benzimidazolylthiomethyl derivatives were synthesized by heating the bromomethyl-substituted derivative with thiourea or with 2-mercaptobenzimidazole. The structures of compounds were confirmed by data of ¹H NMR spectra. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1189–1194, August, 2005.     

Response functions from Fourier component variational perturbation theory applied to a time-averaged quasienergy

It is demonstrated that frequency-dependent response functions can conveniently be derived from the time-averaged quasienergy. The variational criteria for the quasienergy determines the time-evolution of the wave-function parameters and the time-averaged time-dependent Hellmann–Feynman theorem allows an identification of response functions as derivatives of the quasienergy. The quasienergy therefore plays the same role as the usual energy in time-independent theory, and the same techniques can be used to obtain computationally tractable expressions for response properties, as for energy derivatives in time-independent theory. This includes the use of the variational Lagrangian technique for obtaining expressions for molecular properties in accord with the 2n+1 and 2n+2 rules. The derivation of frequency-dependent response properties becomes a simple extension of variational perturbation theory to a Fourier component variational perturbation theory. The generality and simplicity of this approach are illustrated by derivation of linear and higher-order response functions for both exact and approximate wave functions and for both variational and nonvariational wave functions. Examples of approximate models discussed in this article are coupled-cluster, self-consistent field, and second-order Møller–Plesset perturbation theory. A discussion of symmetry properties of the response functions and their relation to molecular properties is also given, with special attention to the calculation of transition- and excited-state properties. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 68: 1–52, 1998     

Structures and reactivities of 2-methyl- and 2-benzyl-3-hydroxypyridines and their N-oxides

It was shown by UV spectroscopy that the introduction of CH₃ and CH₂Ph groups into the 2 position of 3-hydroxypyridine and its N-oxides does not have a substantial effect on the acidbase transformations of these compounds. The effect of methyl and benzyl groups on the electronic and energy characteristics of 3-hydroxypyridine and its N-oxide was studied by means of perturbation theory within the framework of the Hückel MO method. The reactivity indexes (RI) of 2-methyl- and 2-benzyl-3-hydroxypyridines and their N-oxides were calculated, and the RI were correlated with the experimentally observed regularity of the orientation of electrophilic substitution in the indicated compounds.     

Gram scale synthesis of the glucuronide metabolite of ABT-724

A gram scale synthesis of the glucuronide metabolite of ABT-724 is reported. Glycosidic coupling between a trichloroacetimidate glucuronyl donor and a Cbz-protected hydroxypyridylpiperazine glycosyl acceptor is the key step in the synthesis, since attempts to directly glucuronidate the aglycon, aglycon derivatives, and other truncated glycosyl acceptors were unsuccessful. The route was used to produce 2.1 g of metabolite in eight steps from 2-chloro-5-hydroxypyridine in 21% overall yield.     

Hydrogen bonding and molecular association in methylated 3-hydroxypyridines

Association in derivatives of 3-hydroxypyridine has been examined via the chemical shifts for OH in PMR for equimolar mixtures of the derivatives of pyridine and phenol in CCl₄ and CH₂Cl₂. It is found that spatial screening of the pyridine N and phenol OH by methyl groups has an anomalous effect on the strength of the complex. A possible explanation is that the ionic form NH . . . O is stabilized on account of increased basicity of the N and acidity of the H in the methyl derivatives of pyridine and phenol. Domination by the intermolecular hydrogen bond between OH and N is the distinctive feature of association in 3-hydroxypyridines relative to association in phenol. The temperature dependence of _OH gives the enthalpy and entropy of association for 2, 4, 6-trimethyl-3-hydroxypyridine and of complex formation for various model systems. IR measurements confirm the conclusions.See [1] for the previous communication.We are indebted to G. G. Dvoryantseva for making the IR measurements.     

Study on the stereochemical control of dihydroxylation of vinyl epoxides and their derivatives

The results obtained from a study on the stereochemical control in the dihydroxylation of the double bond of vinyl epoxides and their derivatives (bromo derivatives, azido derivatives and vinyl aziridines) are presented herein. A significant diastereoselectivity was observed for the bromo derivatives, azido derivatives and N-protected vinyl aziridines, whereas vinyl epoxides and unprotected vinyl aziridines showed no diastereoselectivity. The results obtained are generally consistent with the Kishi model.     

PMR spectroscopic study of the kinetics of H/D exchange in methyl groups in a series of heterocyclic azines

The rate of H/D exchange among methyl group protons in a series of substituted 3-hydroxypyridines, 5-hydroxypyrimidines, and their N-oxides has been shown to increase with increasing acidity of the medium. The most reactive form of these molecules is the cationic form at pH<2. The rate of H/D exchange of CH₃ group protons in 3-hydroxypyridine derivatives has also been found to be several orders of magnitude lower than the rates of exchange for methyl-substituted 5-hydroxypyrimidine and its N-oxide. Effective rate constants for methyl group proton exchange have been estimated. In the case of methyl-substituted 5-hydroxypyrimidine N-oxide derivatives it has been established that the rate of proton exchange is greater for an ortho-methyl group than for a methyl group in the para-position relative to the N-oxide site.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 93–96, January, 1991.     

Synthesis of 4,5-dihydrothiazole derivatives by the reaction of perfluoro-2-methylpent-2-en-3-yl isothiocyanate with ambident N,O- and N,S-nucleophiles

The reactions of perfluoro-2-methylpent-2-en-3-yl isothiocyanate with ambident N,O- and N,S-nucleophiles (thiazole-2-thione, pyridine-2-thione, 2-hydroxypyridine, benzothiazole-2-thione, benzoxazole-2-thione, 3,4,5,6-tetrahydropyrimidine-2-thione) in the presence of triethylamine yield only 2-N-substituted 4,5-dihydrothiazole derivatives. The molecular structures of three products were determined by X-ray diffraction analysis. The reaction pathways are discussed.     

Cationic Copolymerization of 2-Chloroethyl Vinyl Ether with Styrene Derivatives. III. Solvent and Catalyst Effects on Relative Reactivity

Abstract

The change in relative reactivity in the cationic copolymerization of 2-chloroethyl vinyl ether and styrene derivatives was investigated with various catalysts and solvents. p-Methoxystyrene, p-methylstyrene, and a-methyl-styrene were used as styrene derivatives. The styrene content in the co-polymer increased when a polar solvent and/or a strong catalyst was used. The change of relative reactivity in the copolymerization of 2-chloroethyl vinyl ether with styrene derivatives was much greater than that in the copolymerization between vinyl ethers or styrene derivatives. When nitro-ethane was used as a solvent, not only the polarity but also the nucleophilicity influenced the copolymer composition. The results were discussed by two energies, E^π and E_rs, which are measures of complex formation between monomer and carbonium ion, and stabilization energy in the transition state, respectively.