Showing papers on "Pyridine published in 1979"
TL;DR: Pyridinium poly(hydrogen fluoride) (30% pyridine-70% hydrogen fluoride) reagent, a stabilized, less-volatile form of hydrogen fluoride, was found to be a convenient and effective fluorinating agent as mentioned in this paper.
Abstract: Pyridinium poly(hydrogen fluoride) (30% pyridine-70% hydrogen fluoride) reagent, a stabilized, less-volatile form of hydrogen fluoride, was found to be a convenient and effective fluorinating agent. Fluorination, halofluorination, nitrofluorination, and hydrofluorination of olefins were achieved using the reagent. The in situ diazotization and subsequent fluorinative dediazonization of a-amino acids, aminoarenes, and carbamates yielded a-fluorocarboxylic acids, aryl fluorides, and fluoroformates, respectively. Geminal dihalides and a-halo ketones were reacted with mercuric oxide in pyridinium poly(hydrogen fluoride) to form geminal difluorides and a-fluoro ketones. Solutions of alkali halides in pyridinium poly(hydrogen fluoride) were also found to be effective halogenating agents for aminoarenes, via in situ diazotization and subsequent nucleophilic dediazonization by the corresponding halides, as well as for alcohols, via SN2 type displacement reactions. Diazo ketones and diazoalkanes also reacted smoothly with halide ions in pyridinium poly(hydrogen fluoride) solution to give the corresponding geminally halofluorinated compounds.
418 citations
TL;DR: The infrared spectra of the H-ZSM-5 zeolite calcined at temperatures up to 1173 K, and the corresponding electron spin resonance and microcalorimetric data are discussed in this paper.
287 citations
TL;DR: In this paper, the authors discuss the synthetic routes, physical properties, and reactions of indolizines, including the Tschitschibabinabin reaction involving quaternization of a 2-substituted pyridine, normally using an α-halo carbonyl compound, followed by intramolecular cyclization of the quaternary salt.
Abstract: Publisher Summary This chapter discusses the synthetic routes, physical properties, and reactions of indolizines. One of the synthetic routes presented is Tschitschibabin reaction involving the quaternization of a 2-substituted pyridine, normally using an α -halo carbonyl compound, followed by intramolecular cyclization of the quaternary salt with a mild base, usually aqueous sodium bicarbonate. Another route is ring closure reactions providing indolizines unsubstituted in the five-membered ring. Several physical properties including electronic spectra, acid–base properties, mass spectra, infrared spectra, nuclear magnetic resonance (NMR) spectra and X-ray diffraction are described. The most widely investigated reaction of the indolizine nucleus is electrophilic substitution. The other reactions of indolizines discussed are cyclizations, reduction, oxidation, and polymerization. Cyclization is concerned with reactions that result in the fusion of one or more additional rings to the indolizine system. Various indolizines containing vinyl groups in the pyridine ring are synthesized by polymerization reactions.
128 citations
TL;DR: In this article, the room temperature adsorption of pyridine on η-Al2O3 dehydrated at several temperatures in the 25-700°C range has been studied by i.r. spectroscopy, u.v.-vis reflectance spectrograph and microgravimetry.
Abstract: The room temperature adsorption of pyridine on η-Al2O3 dehydrated at several temperatures in the 25–700°C range has been studied by i.r. spectroscopy, u.v.-vis reflectance spectroscopy and microgravimetry.Several species are formed that can be identified on the basis of the spectroscopic features of the 8a ring mode, whereas the 8b mode, which is common to all species, yields the total amount adsorbed. Quantitative interpretation of the spectral data is carried out using a computer program.The adsorbed species are interpreted as follows: a liquid-like physisorbed species, a species H bonded to surface OH groups through the nitrogen lone pair and three Lewis coordinated species. The latter are assigned to purely octahedral, tetrahedral–octahedral and purely tetrahedral cationic sites, respectively.The reactions occurring upon Py desorption above 400°C are discussed and a different interpretation is given to that in the literature.
116 citations
TL;DR: In this article, coal was converted by methanol/KOH systems to a product which was extractable by pyridine fully, and 15-25% of the mixture was enriched in hydrogen relative to the starting coal.
115 citations
TL;DR: The capacity of cyclopentadienylsodium to form adducts with the following bases has been studied: diethyl ether, tetrahydrofuran, 1,2-dimethoxyethane, 1 4-dioxane, benzo-15-crown-5, triethylamine, tetramehtylethylenediamine, pyridine, 4-dimethylaminopyridine and 2,2′ bipyridryl Most form extremely air-and moisture-sensitive 1 : 1 adduct
81 citations
TL;DR: The adsorbed states of benzene, pyridine, aniline, and nitrobenzene on evaporated nickel and iron films have been investigated by X-ray photoelectron spectroscopy.
74 citations
TL;DR: In this paper, Nitrogen chemical shifts are used to estimate equilibrium compositions of tautomeric systems of mercapto-and amino-derivatives of pyridine, which can provide qualitative information about such equilibria.
Abstract: Nitrogen chemical shifts are shown to provide a means of estimating equilibrium compositions of tautomeric systems of mercapto- and amino-derivatives of pyridine. Carbon chemical shifts can afford only qualitative information about such equilibria.
71 citations
TL;DR: In this article, the cation-radical of pyridine is shown to be a σ-type radical, the positive charge residing mostly in the nitrogen lone pair orbital.
68 citations
TL;DR: In this article, the thermal intercalation of pyridine with 2H-TaS2 is associated with redox reactions involving guest layers and host molecules, and the reaction product is discussed in terms of a novel ionic bonding concept.
65 citations
TL;DR: In this paper, the infrared spectra have been recorded of haematite in contact with ammonia, pyridine, nitric oxide, carbon dioxide, acetic acid and trimethylchlorosilane.
Abstract: Infrared spectra have been recorded of haematite in contact with ammonia, pyridine, nitric oxide, carbon dioxide, acetic acid and trimethylchlorosilane. Ammonia and pyridine were adsorbed onto weak Lewis acidic surface sites on haematite which had been heated in oxygen at 713 K. No detectable Lewis acidic sites existed on haematite which had been heated at 973 K. No evidence was observed for the adsorption of nitric oxide on haematite and carbon dioxide only gave a single weak band in spectra at 1320 cm–1. Acetic acid was chemisorbed to give surface acetato species possibly in three distinct configurations. Surface hydroxyl groups on haematite reacted with trimethylchlorosilane vapour to give hydrogen chloride, which was in part adsorbed, and surface trimethylsiloxyl groups. The relative reactivities of different types of surface hydroxyl group could be distinguished.
TL;DR: A new complex, aquaoxo[N-(2-pyridylmethyl)iminodiacetato]vanadium(IV) dihydrate [VO(pmida)(H2O)]·2H 2O has been synthesized and its crystal structure determined by the X-ray method as discussed by the authors.
Abstract: A new complex, aquaoxo[N-(2-pyridylmethyl)iminodiacetato]vanadium(IV) dihydrate [VO(pmida)(H2O)]·2H2O has been synthesized and its crystal structure determined by the X-ray method. The triclinic crystals obtained from water or aqueous ethanol solution are twinned and contain 2 mol of lattice water. The unit cell contains four formula units and the structure was analyzed on the assumption that the space group is P\bar1. The positional and thermal parameters were refined to R=0.115. The vanadium atom has a distorted octahedral coordination and deviates by 0.39 A from the equatorial plane, which is composed of two cis carboxylate oxygens, a water molecule and the pyridine nitrogen. Vanadyl oxygen and tertiary nitrogen occupy the axial sites. Absorption spectra indicated that the structure is maintained in an aqueous solution of pH 3.0 to 4.9. This geometrical isomer seems to be formed selectively in an aqueous medium.
TL;DR: Pentamethylcyclopentadienyl halostannanes are accessible by alkylation of tin tetrachloride and organotrichlorostannes with organolithium compounds and by oxidative addition reactions with decamethylstannocene, whose synthesis was also described as discussed by the authors.
TL;DR: In this paper, partial O-deacylation of fully acylated purine and pyrimidine ribonucleosides upon hydrazinolysis was found to be induced regioselectively in respect to the three ester functions at the 2′-position.
Abstract: In 1 : 4 (v/v) glacial acetic acid–pyridine, partial O-deacylation of fully acylated purine and pyrimidine ribonucleosides upon hydrazinolysis was found to be induced regioselectively in respect to the three ester functions at the 2′-position to give the corresponding 2′-OH derivatives in good yields; e.g. 3′, 5′-di-O-benzoyladenosine (70% yield), N2, 3′, 5′-tribenzoylguanosine (63% yield), 3′, 5′-di-O-benzoylinosine (52% yield), N2-benzoyl-3′, 5′-di-O-acetylguanosine (42% yield), and 3′, 5′-di-O-benzoyluridine (39% yield) were isolated. Moreover, 5′-O-acylribonucleosides were prepared in quantitative yields by use of an excess of hydrazine hydrate in 1 : 1 (v/v) chloroformmethanol and in pyridine. Hydrazinolysis of 3′, 5′-di-O-acetyl-2′-deoxyribonucleosides in pyridine was found to give both 5′, and 3′-O-acetyl-2′-deoxyribonucleosides in comparable amounts (80–90% total yields).Furthermore, hydrazinolysis of N6, 2′, 5′-triacetyl-3′-O-methyladenosine and N6, 3′, 5′-triacetyl-2′-O-methyladenosine demonstrated that the 2′-O-acetyl group is far more labile toward the nucleophile than the 3′-O-acetyl group.The possible factors involved in the regioselectivity of hydrazinolysis are discussed.
TL;DR: In this paper, the acidity of offretite zeolites has been studied as a function of the amount of potassium in the gmelinite windows and the removal of the last three potassium cations creates strong acid sites and allows reaction molecules to enter the cages, and two types of Lewis acidity are suggested to arise from partial dehydroxylation during pyridine evacuation.
TL;DR: In this article, a one-pot preparation of α,β,unsaturated nitriles from ketones with trimethylsilyl cyanide in benzene in the presence of a Lewis acid (ZnI2) as a catalyst and subsequent heating after addition of pyridine and phosphoryl chloride has been presented.
Abstract: Treatment of ketones with trimethylsilyl cyanide in benzene in the presence of a Lewis acid (ZnI2) as a catalyst and subsequent heating after addition of pyridine and phosphoryl chloride have given α,β,-unsaturated nitriles in good yields, providing a general one-pot preparation of α,β,-unsaturated nitriles from ketones.
TL;DR: In this article, the presence of water was found to be essential to maintain the Keggin structure of 12-molybdophosphoric acid (PMo12), which was almost pure Bronsted acid as seen from IR spectra of adsorbed pyridine.
Abstract: Presence of water was found to be essential to maintain the Keggin structure of 12-molybdophosphoric acid (PMo12). Hydronium ion was detected by IR at high water contents. PMo12 was almost pure Bronsted acid as seen from IR spectra of adsorbed pyridine. Dependencies of the spectra on time, temperature, and presence of water were discussed in relation to the characteristic surface properties of PMo12.
TL;DR: In this article, the authors used aqueous NaOCl at 30 °C to oxidize Illinois No. 6 coal, mostly as insoluble residues of pyridine extractions, to yield several products, ranging from black, bicarbonate-soluble acids of molecular weight as high as 1000 to nearly colourless, water soluble acids with molecular weights near 300.
TL;DR: In this article, a single-crystal X-ray diffraction study has been made on the chloro-derivative of (1bβ) and the bromo-deletion of ( 1bα), and the structure has been refined to R 0.074 (R′ 0.105) for 2 529 independent reflections.
Abstract: Reactions between disubstituted alkynes RC2R′(R = R′= Ph and R = Me, R′= Ph) and [{Pd(dmba)X}2](dmba =NN-dimethylbenzylamine, X = Cl or Br) afford bis-insertion products [Pd{(RCCR′)2C6H4CH2NMe2}X] in high yield. With MeC2Ph two isomers have been isolated, (1bα) and (1bβ). In order to establish their molecular structures, a single-crystal X-ray diffraction study has been made on the chloro-derivative of (1bβ) and the bromo-derivative of (1bα). Crystals of (1bα; X = Br) are monoclinic, space group P21/c, Z= 4, with a= 15.362(13), b= 12.368(5), c= 14.886(11)A, and β= 94.86(13)°. The structure has been refined to R 0.078 (R′ 0.105) for 2 529 independent reflections; the two acetylenes inserted into the Pd–C bond have a head-to-tail arrangement, the Pd being σ-bonded to a carbon bearing a phenyl group. Crystals of (1bβ; X = Cl) are monoclinic, space group P21, Z= 2, with a= 8.227(6), b= 16.059(33), c= 8.923(9)A, and β= 99.30(12)°. The structure has been refined to R 0.074 (R′ 0.065) for 2 077 independent reflections. The molecule shows a tail-to-tail arrangement for the two inserted acetylenes, the carbon σ-bonded to the palladium bearing a methyl group. The corresponding reaction with the 8-methylquinoline palladated dimer affords a benzenoid trimer via a bis-insertion analogue which was isolated for R = R′= Ph. Hexafluorobut-2-yne (hfb) reacts with the above palladated dimers and those formed from benzo[h]quinoline and NN-dimethyl-1-naphthylamine to give novel halide-bridged binuclear complexes with seven-membered rings. They are formed by formal insertion of one hfb unit into the Pd–C σ bond. With the naphthylamine dimer only an organic compound was isolated. The novel dimeric complexes easily afford monomeric derivatives by bridge-splitting reactions with pyridine or PPh3.
TL;DR: The oxidative aromatic ring cleavage of 3,5-di-t-butylcatechol by molecular oxygen to give the lactone is catalysed by a non-enzymatic iron(II) complex co-ordinated by 2,2′-bipyridine and pyridine.
Abstract: The oxidative aromatic ring cleavage of 3,5-di-t-butylcatechol (1) by molecular oxygen to give the lactone (2) is catalysed by a non-enzymatic iron(II) complex co-ordinated by 2,2′-bipyridine and pyridine.
TL;DR: In this article, a single-step synthesis of (2-Me2NCHZC6H4)RSnX2 is described, in which Z H or Me, R Me or Ph and X Cl or Br or Br, starting from the tetranuclear copper cluster compound (2 -Me2NCZC 6H4), 4Cu4 and RSnX3 is described.
TL;DR: In this article, the intercalation of C5D5N into the lattice of 2HTaS2 was followed by neutron powder diffraction using deuteropyridine as liquid phase.
TL;DR: In this article, two series of rare earth compounds of the anion 2-thiopyridine Noxide have been isolated and characterized (i.e. Ln = La, Pr, Sm, Eu, Tb and Er).
TL;DR: In this paper, pyridine derivatives were intercalated into the van der Waals gap of layered compound FeOCl, and some correlations were found between the measured parameters of these complexes and the basicities of organic intercalates.
Abstract: Some pyridine derivatives were intercalated into the van der Waals gap of layered compound FeOCl. Pyridine, 2,6-dimethylpyridine, 4-aminopyridine, 2,4,6-trimethylpyridine, and n-propylamine were used as intercalates having different Lewis basicities. X-Ray diffraction, Mossbauer effect, electrical resistivity, ESR and electronic spectra were studied, some correlations being found between the measured parameters of these complexes and the basicities of organic intercalates. It is assumed that organic intercalates transfer their lone pair electrons on the nitrogen atom to FeOCl layers.
TL;DR: In this paper, the vapor phase oxidation of benzyl alcohol catalyzed by Y-type zeolite has been investigated in a flow system with reaction temperature between 300 to 390 °C.