Dissociation energies of O–H bonds in 3-pyridinols

The O?H bond dissociation energy (D _O?H) has been estimated for 20 substituted 3-pyridinols and a substituted 3-pyrimidinol from experimental kinetic data by the intersecting parabolas method using α-tocopherol and 4-methoxyphenol as reference compounds. The following D _O?H values (kJ/mol) have been obtained: 363.7 for 3-pyridinol, 365.3 for 2-alkyl-3-pyridinols (five compounds), 358.8 for 2-alkyl-6-methyl-3-pyridinols (six compounds), 378.1 for 5-benzyl-3-pyridinol, 353.2 for 2,4,6-trimethyl-3-pyridinol, 340.9 for 2-benzyl-6-methoxy-3-pyridinol, 345.8 for 2,6-dimethoxy-5-benzyl-3-pyridinol, 381.7 for 2-ethyl-4-nitro-6-methyl-3-pyridinol, 376.8 for 2-isopropyl-4-nitro-6-methyl-3-pyridinol, 318.3 for 2,4-dimethyl-6-dimethylamino-3-pyridinol, 357.3 for mexidol, and 322.2 for 2,4-dimethyl-6-dimethylamino-3-pyrimidinol. The substituent effect on the O?H bond dissociation energy in 3-pyridinols is considered. The stabilization energies of pyridinoxyl and phenoxyl radicals are compared. The activation energies and rate constants have been calculated for a series of reactions of various radicals with 3-pyridinols.     

An infrared study of the tautomerism of chlorinated 2-pyridinols isolated in an argon matrix

The infrared spectra of 3-, 4-, 5- and 6-monochloro-, 3,5,6-trichloro-2-pyridinols (pyridones), and of the unsubstituted 2-pyridinol isolated in a low temperature (20°K) argon matrix were studied. The results indicate that the enol/keto ratio for the isolated pyridinols decreases according to the position of the chlorine atom(s) on the pyridine ring; i.e., 3,5,6-trichloro >-6 > 5 > 4 > 3 monochloro-2-pyridinols. 3,5,6-Trichloro-2-pyridinol exists predominantly in the enol form.     

Synthesis of 4-alkyl-3-pyridinols from 3-benzyloxypyridine

The addition of Grignard reagents to the 1-phenoxycarbonyl salt of 3-benzyloxypyridine and a catalytic amount of cuprous iodide afforded 4-alkyl-3-benzyloxy-1-phenoxycarbonyl-1,4-dihydropyridines in good yield. The crude dihydropyridines were aromatized with o-chloranil to give 4-alkyl-3-benzyloxypyridines, which were debenzylated with hydrogen and 10% palladium on carbon to provide 4-alkyl-3-pyridinols.     

Pulse radiolysis studies of 4-pyridinol: Evidence for dimer anion formation

Rate constants for the reactions of 4-pyridinol with e^-_aq and OH/O^- species were determined at different pHs. The spectral and kinetic characteristics of product transient species formed have been assessed. It has been found that semireduced 4-pyridinol forms dimer anions on reaction with the parent molecule. Equilibrium constant for the dimer formation has been determined to be 97 dm³ mol^-1. Reactions of 4-pyridinol with radiolytic species have been compared with those of 2- and 3-pyridinols investigated and reported earlier.     

Isolation and Structural Study on Carbohydrates from Cynanchum otophyllum and Cynanchum paniculatum

Three new carbohydrates were isolated from the acidic hydrolysis part of the ethyl acetate extract of Cynanchum otophyllum Schneid (Asclepiadaceae) and one new carbohydrate from the ethyl acetate extract of Cynanchum paniculatum Kitagawa. Their structures were determined as methyl 2,6-dideoxy-3-O-methyl-α-D-arabino-hexopyranosyl-(1 → 4)-2,6-deoxy-3-O-methyl-β-D-arabino-hexopyranosyl-(1 → 4)-2,6-dideoxy-3-O-methyl-α-D-arabino-hexopyranoside (1), ethyl 2,6-dideoxy-3-O-methyl-β-D-ribo-hexopyranosyl-(1 → 4)-2,6-dideoxy-3-O-methyl-α-l-lyxo-hexopyranoside (2), met hyl 2,6-dideoxy-3-O-methyl-α-l-ribo-hexopyranosyl-(1 → 4)-2,6-dideoxy-3-O-methyl-β-D-lyxo-hexopyranosyl-(1 → 4)-2,6-dideoxy-3-O-methyl-α-D-arabino-hexopyranoside (3), and 2,6-dideoxy-3-O-methyl-β-D-ribo-hexopyranosyl-(1 → 4)-2,6-dideoxy-3-O-methyl-α-d-arabino-hexopyranosyl-(1 → 4)-2,6-dideoxy-3-O-methyl-α -d-arabino-hexopyranose (4), respectively, by spectral methods.     

Carbonation of 3-pyridinols

Procedures are described for the high pressure carbonation of substituted 3-pyridinols, yielding the corresponding pyridine carboxylic acids. Treatment of o-aminohydroxypyridinecarboxylic acid with cyanogen and with phosgene, respectively, gave access to oxazolo[4,5-b]pyridine derivatives. The synthesis of 3-amino-6-methyl-2-pyridinecarboxylic acid was accomplished by heating 3-hydroxy-6-methyl-2-pyridinecarboxylic acid in liquid ammonia.     

Stereoselective reductive tetraallylation of pyridinecarboxylic acids with triallylborane

Reductive tetraallylation of pyridine-3-and pyridine-4-carboxylic acids with triallylborane in the presence of propan-2-ol proceeded stereoselectively to yieldtrans-2,6-diallyl-3- andtrans-2,6-diallyl-4-(1-allyl-1-hydroxybut-3-en-1-yl)-1,2,5,6-tetrahydropyridines, respectively. Under the same conditions, the reaction with pyridine-2-carboxylic acid gave a mixture oftrans- andcis-2,6-diallyl-2-(1-allyl-1-hydroxybut-3-en-1-yl)-1,2,5,6-tetrahydropyridines in a ratio of 57:43. When 2,6-diphenylpyridine-4-carboxylic acid reacted with triallylborane, only the carboxylic group underwent reductive diallylation. When heated with triallylborane ino-xylene (130–133°C, 7 h),trans-2,6-diallyl-4-(1-allyl-1-hydroxybut-3-en-1-yl)-1,2,3,6-tetrahydropyridine was converted to the correspondingcis-isomer. The stereochemistry oftrans-2,6-diallyl-3-(1-allyl-1-hydroxybut-3-en-1-yl)-1,2,5,6,-tetrahydropyridine was confirmed by X-ray diffraction analysis. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2320–2326, November, 1998.     

一种咔唑类衍生物的合成及其探针性能研究

用两步简便方法合成了基于咔唑基的荧光探针2,6-二(9-乙基咔唑-3氨甲基)-4-叔丁基苯酚,并对其光谱性能和离子选择性进行了研究.结果表明:在pH=7.4的体系中,该化合物对铜离子具有较强的选择性,铜离子的出现使得该探针在438nm处的荧光猝灭,且猝灭程度和铜离子浓度之间呈现良好的线性关系.     

Stereoselective synthesis of 2-substituted 6-[1-(2,6-difluorophenyl)ethyl]-5-methylpyrimidin-4(3<Emphasis Type="Italic">H</Emphasis>)-ones

A procedure has been proposed for the synthesis of 2-(cyclopentylsulfanyl)-6-[(1R)-1-(2,6-difluorophenyl) ethyl]-5-methylpyrimidin-4(3H)-one through intermediate (3R)-4,4-dimethyl-2-oxotetrahydrofuran-3-yl (2R)-2-(2,6-difluorophenyl)propanoate which was obtained from prochiral 2-(2,6-difluorophenyl)prop-1-en-1-one generated in situ. The proposed procedure may be regarded as stereoselective route to 6-[(1R)-1-(2,6- difluorophenyl)ethyl]-5-methylpyrimidin-4(3H)-one derivatives.     

A convenient large scale synthesis of 2,6-dimethyl-4-(trimethylstannyl)pyridine

Reaction of phosphorus oxychloride with 2,6-dimethylpyridine N-oxide hydrochloride ( 1 ) gave a mixture of 2-(chloromethyl)-6-methylpyridine ( 2 ) and 4-chloro-2,6-dimethylpyridine ( 3 ). Treatment of this mixture with triethylamine converted 2 to the quaternary salt 4 which was separated by water extraction leaving 3 which was subsequently reacted with trimethylstannyl sodium to yield 2,6-dimethyl-4-(trimethylstannyl)pyridine ( 6 ).     

4-Oxo-3,4-dihydroquinazolinyl- and Benzimidazolylacetonitriles in Annelation Reactions of a Haloquinoline Ring

The interaction of 4-oxo-3,4-dihydroquinazolinyl- and benzimidazolylacetonitriles with 2,6-dihalobenzaldehydes leads to 3-(2,6-dihalophenyl)-2-(4-oxo-3,4-dihydro-2-quinazolinyl)acrylonitriles and 2-(1H-benzo[d]imidazol-2-yl)-3-(2,6-dihalophenyl)acrylonitriles respectively. As a result of intramolecular cyclization of these nitriles 4-halo-12-oxo-12H-quino[2,1-b]quinazoline-6-carbonitriles and 4-halobenzo[4,5]imidazo[1,2-a]quinoline-6-carbonitriles respectively are formed.     

In vitro microbial studies of new pyrazolyl quinazolin-4(3H) ones

A series of new 2-[2-(2,6-dichlorophenyl)amino]phenyl methyl-3-[(5-substituted phenyl)-1,5-dihydro-1H-pyrazol-3-yl-amino]-6-iodoquinazolin-4(3H) ones (6a–m) have been synthesized by the reaction of 2-[2-(2,6-dichlorophenyl)amino]phenyl methyl-3-substituted phenyl acryl amido-6-iodoquinazolin-4(3H) ones with hydrazine hydrate in the presence of glacial acetic acid. The chalcone (5a–m) have been prepared by the condensation of 2-[2-(2,6-dichlorophenyl)amino]phenyl methyl-3-acetamido-6-iodoquinazolin-4(3H) one with different substituted aromatic aldehyde. The compound 1 on treatment with 5-iodoanthranilic acid in pyridine undergoes cyclisation gave 2-[2-(2,6-dichlorophenyl)amino]phenyl methyl-6-iodo-3,1-benzoxazin-4(3H) one (2). Treatment on benzoxazine with hydrazine hydrate gave 3-amino-2-[2-(2,6-dichlorophenyl)amino]phenyl methyl-6,8-dibromo quinazolin-4(3H) one (3) followed by acetylation synthesized 2-[2-(2,6-dichlorophenyl)amino]phenyl methyl-3-acetamido-6,8-dibromoquinazolin-4(3H)-one (4). The structure of synthesized compounds has been elucidated by IR, ¹H NMR, ¹³C NMR and elemental analysis. The products were screened for antibacterial and antifungal activity. Among the series containing some of the compounds showed promising results against standard drugs.     

Facile addition of methyl lithium to a 4-vinylpyridine system

The rapid addition of methyl lithium to the 4-vinylpyridine system present in 4-{2,6-dihydroxy-4-(3-methyl-2-octyl)phenyl}-2-methyl-4-(4-pyridyl)but-3-en-2-ol ( 2 ) is reported. The α and β-4-{2,6-dihydroxy-4-(3-methyl-2-octyl)phenyl}-2,3-dimethyl-4-(4-pyridyl)butan-2-ols 4 and 5 formed, are cyclised by heating with 5N hydrochloric acid to trans and cis-3,4-dihydro-5-hydroxy-7-(3-methyl-2-octyl)-4-(4-pyridyl)-2,2,3-trimethyl-2H-1-benzopyran 6 and 7 respectively.     

Cyclodextrin derivatives for GC separation of racemic mixtures of volatile compounds. Part VIII: 2,6-di-O-methyl-3-O-pentyl-γ-cyclodextrin and 2,6-di-O-methyl-3-O-(4-oxo-pentyl)- and 2,6-di-O-pentyl-3-O-(4-oxo-pentyl)-β-and -γ-cyclodextrins

In pre vious papers, 2,6-di-O-methyl-3-O-pentyl-β-cyclodextrin (CD) was demonstrated to be successful in separating volatile compounds, while avoiding the drawbacks of 2,3,6-tri-O-methyl-O-methyl-β-CD in terms of column stability and operating temperature. Since a CD chiral selector of universal use has not yet been found, and at least two (or more) columns coated with different CD derivatives are therefore necessary for routine work, the performance of 2,6-di-O-methyl-3-O-pentyl-γ-CD, 2,6-di-O-methyl-3-O-(4-oxopentyl)-γ-CD, 2,6-di-O-pentyl-3-O-(4-oxo-pentyl)-β-CD, and 2,6-di-O-pentyl-3-O-(-4-oxo-pentyl)-γ-CD diluted in polysiloxanes for the separation of volatile compounds in aromas and essential oils will be illustrated; each column coated with each of the newly synthesized CD derivatives was evaluated by analyzing more than 150 different recemates with different structures.     

Reactions of 4-dicyanomethylenepyrans with hindered primary amines

The reaction of 2,6-dimethyl- and 2,6-diphenyl-4-dicyanomethylene-4H-pyran with hindered primary amines such as isopropylamine and cyclohexylamine gave 1-alkyl-2-amino-3-cyano-6-rnethyl(or phenyl)-4-acetonylidene (or phenacylidene)-1,4-dihydropyridine derivatives. The 6-methyl-4-acetonylidene examples underwent a facile thermal rearrangement to give 1-alkyl-2,6-dimethyl-4-dicy anomethy lene-1,4-dihydropy ridines. Several reactions of the acylidene derivatives are described.     

Synthesis of 3-oxoesters and functional derivatives of pyrimidin-4(3<Emphasis Type="Italic">Н</Emphasis>)-one based on 1-(2,6-dihalophenyl)cyclopropan-1-carboxylic acids

Special features of the synthesis and chemical transformations of novel functional derivatives of 6-[1-(2,6-dihalophenyl)cyclopropyl]pyrimidin-4(3H)-one and ethyl esters of 3-[1-(2,6-dihalophenyl)cyclopropyl]-2-methyl-3-oxopropanoic acids prepared from 2-(2,6-dihalophenyl)acetonitriles have been revealed. Novel achiral structural analogs of experimental anti-HIV agent МС-1501 have been synthesized.     

New chiral 3-aryl-7-arylmethylidene-3,3a,4,5,6,7-hexahydroindazoles: Synthesis,structure, and twisting power in nematic liquid crystals

(3R)-2,6-Bis(arylmethylidene)-3-methylcyclohexanones and 3-(4-X-aryl)-7-(4-X-arylmethylidene)-3,3a,4,5,6,7-hexahydro-2,6- and -2,4-dimethyl-2H-indazoles (X = Cl, HO, AlkO, AlkOCO, MeOC₆H₄COO) as potential chiral additives to liquid crystalline systems were synthesized starting from (3R)-3-methylcyclohexanone. Relations between the twisting power and molecular structure of the synthesized compounds are discussed.     

Rhodiolosides A-E, monoterpene glycosides from Rhodiola rosea

Five new monoterpene glycosides, rhodiolosides A-E (1-5), were isolated from the roots of Rhodiola rosea (Crassulaceae). Their structures were elucidated as (2E,6E,4R)-4,8-dihydroxy-3,7-dimethyl-2,6-octadienyl beta-D-glucopyranoside (1), (2E,4R)-4-hydroxy-3,7-dimethyl-2,6-octadienyl alpha-D-glucopyranosyl(1-->6)-beta-D-glucopyranoside (2), (2E,4R)-4-hydroxy-3,7-dimethyl-2,6-octadienyl beta-D-glucopyranosyl(1-->3)-beta-D-glucopyranoside (3), (2E,4R)-4,7-dihydroxy-3,7-dimethyl-2-octenyl beta-D-glucopyranoside (4), and (2E)-7-hydroxy-3,7-dimethyl-2-octenyl alpha-L-arabinopyranosyl(1-->6)-beta-D-glucopyranoside (5), on the basis of various spectroscopic analyses and chemical degradation.     

Synthesis and Antibacterial Activity of Some Substituted 3-(Aryl)- and 3-(Heteroaryl)indoles

Summary. A synthesis of 3-(4-methoxycarbonyl-2,6-dinitrophenyl)indole, its 2,6-diamino analog, and 3-(2-amino-4-trifluoromethyl-6-nitrophenyl)indole is described. 4-(Trifluoromethyl)phenyl derivatives exhibit higher antibacterial potency than the former 4-(methoxycarbonyl)phenyl homologs, while 3-(4-trifluoromethyl-2-nitrophenyl)indole was the most active agent in the series, with MIC ≈ 7 μg/cm³ against E. coli and S. aureus.     

Anomalous transformations of acetaldehyde (2,6-dichloro-4-pyridyl)hydrazone under the conditions of the Fischer reaction

Instead of the usual indolization, when acetaldehyde (2,6-dichloro-4-pyridyl)hydrazone is heated with zinc chloride under the conditions of the Fischer reaction one observes the formation of acetone (2,6-dichloro-4-pyridyl)hydrazone, 1-(2,6-dichloro-4-pyridyl)-5-methylpyrazoline, and 2,6-dichloro-4-aminopyridine, the ratio between which depends on the temperature and duration of the reaction.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 374–377, March, 1973.