Pyrrole Type Research Articles

Application of Atmospheric Pressure Photo Ionization Hydrogen/Deuterium Exchange High-Resolution Mass Spectrometry for the Molecular Level Speciation of Nitrogen Compounds in Heavy Crude Oils

We report here for the first time the application of atmospheric pressure photo ionization hydrogen/deuterium exchange (APPI HDX) coupled to high-resolution mass spectrometry for molecular level speciation of nitrogen containing compounds in crude oils. The speciation was done based on different combinations of ions produced from nitrogen containing compounds with various functional groups. To prove the concept, 20 nitrogen containing standard compounds were analyzed. As a result, it was shown that the nitrogen containing compound (M) with a primary amine functional group mainly produced a combination of [M - 2H + 2D](•+) and ([M - 2H + 2D] + D)(+) ions, one with a secondary amine including alkylated or phenylated pyrrole a combination of [M - H + D](•+) and ([M - H + D] + D)(+), one with a tertiary amine including N-alkylated or phenylated pyrrole a combination of [M](•+) and [M + D](+), and one with a pyridine functional group mostly [M + D](+) ions. The concept was successfully applied to do nitrogen speciation of resins fractions of two oil samples. Combined with the subsequent investigation of double bond equivalence distribution, it was shown that resins of Qinhuangdao crude oil sample contained mostly alkylated pyrrole and N-alkylated pyrrole type compounds but resins of shale oil extract contained mostly pyridine type nitrogen compounds. It was also shown that the speciation of individual elemental composition was also possible by use of this method. Overall, this study clearly shows that atmospheric pressure photo ionization hydrogen/deuterium exchange (APPI HDX) coupled to high-resolution mass spectrometry is a powerful analytical method to do nitrogen speciation of crude oil compounds at the molecular level.

Scalable synthesis of pyrrolic N-doped graphene by atmospheric pressure chemical vapor deposition and its terahertz response

Atmospheric pressure chemical vapor deposition is employed to synthesize the N-doped graphene, which is mainly composed of pyrrolic type N bonding configuration with a controllable doping concentration from ∼1.6% to ∼6.4%. Transmission electron microscope, X-ray photoelectron spectroscopy, and Raman spectrometer are used for characterizing the pyrrolic N-doped graphene. X-ray photoelectron spectra confirm the dominant pyrrolic N bonding configuration, which is consistent with the Raman spectra compared with the pristine graphene. THz time-domain spectroscopy, four-probe DC electrical measurements, and visible spectroscopy are also utilized to analyze doping concentration qualitatively.The investigation suggests that THz wave is sensitive to the dopant concentration, which is relevant to the conductivity, while the visible light is insensitive to the dopant concentration. Our results further extend the synthesis method of N-doped graphene and the new type doped graphene might have potential applications in electrochemistry, electronics, photonics, and THz devices.

ChemInform Abstract: Rearrangement of the Adducts of α‐(Aminocarbonyl)acetamidoximes with Acylacetylenes, Leading to 2‐Aminopyrrole Derivatives.

AbstractO‐Vinylamidoximes [cf.

Iridium‐Catalyzed Asymmetric Hydrogenation of Pyridinium Salts

As one of the most straightforward and powerful approaches for the preparation of optically active compounds, asymmetric hydrogenation has been successfully used for different types of aromatic compounds, including quinolines, isoquinolines, quinoxalines, indoles, pyrroles, furans, imidazoles, and aromatic carbocyclic ring, with excellent enantioselectivities. Despite these advances, direct hydrogenation of simple pyridines is still a challenge. The inherent problems are apparent: First, substrates and corresponding products that possess strong coordination ability might cause the deactivation of catalysts. Second, pyridines have a stabilizing aromatic structure that might impede the reduction. Therefore, only limited examples of hydrogenation of specific pyridine derivatives bearing powerful electron-withdrawing substituent at the 2or 3-position have been previously described. In 2000, Studer et al. reported the first homogeneous rhodium-catalyzed asymmetric hydrogenation of pyridines, but only poor enantioselectivity was obtained. Zhang and co-workers described an efficient three-step rhodium-catalyzed asymmetric hydrogenation of nicotinates. Subsequently, the group of Rueping documented the first enantioselective organocatalytic transfer hydrogenation of 3-cyanoor carbonyl-substituted pyridines using Hantzsch esters as hydrogen sources, and our group also employed [{Ir(cod)Cl}2]/(S)-MeO-biphep/I2 catalyst system for asymmetric hydrogenation of specific pyridines with excellent enantioselectivities. Additionally, an elegant asymmetric hydrogenation of activated pyridines, that is, N-iminopyridinium ylides, was developed by Charette et al. As chiral piperidines are important building blocks for the synthesis of biologically active molecules and natural products, the development of an efficient strategy for the highly challenging hydrogenation of the simple pyridines is still of great significance. Iminium salts generally exhibit higher activity than the corresponding imines in hydrogenation, therefore we envisioned that the activation of simple pyridines as the corresponding N-benzyl-pyridinium bromides would effectively eliminate coordination ability of the substrate and thus the reactivity could be greatly enhanced. Moreover, the stoichiometric amount of hydrogen bromide generated in situ would effectively inhibit the coordination ability of the desired product through the formation of its piperidine hydrogen bromide salt (Scheme 1). Also, the benzyl protecting groups could be conveniently removed by hydrogenolysis. Herein, we disclose the iridium-catalyzed asymmetric hydrogenation of 2-substituted pyridinium salts with excellent enantioselectivity.

Rearrangement of the adducts of α-(aminocarbonyl)-acetamidoximes with acylacetylenes, leading to 2-aminopyrrole derivatives*

-vinylacetamidoximes, which are adducts of α-(amino-carbonyl)acetamidoximes with esters of propiolic and acetylenedicarboxylic acids. Various types of pyrroles are formed as a result of this rearrangement [17, 18]. The present work is devoted to investigation of the direction and synthetic potential of the rearrangement of

Kinetic study of fuel NO formation from pyrrole type nitrogen

An experimental study using a flow reactor and a numerical simulation with a detailed kinetic model have been performed to investigate the reaction mechanism of NO formation from pyrrole decomposition. The experiments have been conducted in a quartz flow reactor by using a mixture gas of pyrrole, O2 and H2O with N2 as a balance gas at atmospheric pressure and temperature range 800–1400K. The detailed kinetic model consists of 505 elementary reactions and 89 chemical species, and the plug flow calculations have been carried out under same conditions as experiments. Model predictions are in reasonably good agreement with the experimental data for NO formation from pyrrole. Model predictions indicate that the main reaction pathways from pyrrole to HCN are direct reaction by pyrrole pyrolysis and pyrolysis reaction of HNCPROP (HNCHCHCCH2) generated by ring scission reaction of pyrrole. HCN is converted to N2 or NO via NCO and about 90% of nitrogen in pyrrole is transformed to N2 or NO at the temperature of above 1400K. The residence time has little influence on the reaction rate and the reaction rate largely depends on the reaction temperature.

ChemInform Abstract: Oxidation of Pyrrole‐2‐carboxylates with o‐Chloranil and Its Synthetic Application.

t-Butyl 3,4-dialkyl-1H-pyrrole-2-carboxylates were oxidized with o-chloranil in the presence of MeOH to afford the corresponding 5-methoxypyrrolin-2-one derivatives. The resulting 5-methoxypyrrolin-2-one was reacted with various nucleophiles under acidic conditions to afford the functionalized pyrrolinone derivatives in good yields. Toward elucidation of the structure and function of the linear tetrapyrrole (bilin) chromophores in phytochromes, we have succeeded in synthesizing phytochromobilin (PΦB), phycocyanobilin (PCB), modified PCBs, biliverdin (BV) and its analogs including sterically locked derivatives in free acid forms by developing efficient methods for the preparation of each pyrrole ring and a new coupling reaction between them. In order to synthesize different types of locked chromophores, it was necessary to prepare various pyrrole and pyrrolinone derivatives bearing a wide variety of functional groups. In our previous syntheses, pyrrole rings with an electron withdrawing group were constructed by a modified Barton reaction starting from aldehydes, 1-nitroalkanes, and isonitrile compounds. The produced tosyland ester-substituted pyrroles were converted into Aor D-ring and Bor C-ring, respectively. It would be ideal for the synthesis of the locked bilin chromophores if the various types of pyrroles and the related pyrrolinones could be available from a common pyrrole by a simple manipulation. Recently we have developed a regioselective oxidation of the α-position of the C-4 substituents on t-butyl pyrrole-2-carboxylates with DDQ and the subsequent substitution reaction via azafulvene intermediates (Scheme 1). Herein we describe an oxidation of t-butyl pyrrole-2-carboxylates with o-chloranil and its application toward the synthesis of various types of functionalized pyrrolinone derivatives. N H CO2 tBu DDQ AcOH N H CO2 tBu R OAc R Nu base N H CO2 tBu Nu

Atividade farmacológica da monocrotalina isolada de plantas do gênero Crotalaria

Crotalaria retusa e uma planta encontrada no Nordeste brasileiro, pertence ao genero Crotalaria e a familia Leguminosae, e possuem mais de seissentas especies no mundo e mais de quarenta no Brasil. As variedades toxicas mais conhecidas sao C. spectabilis, C. crispata, C. retusa, C. dura e C. globifera. Plantas do genero Crotalaria sao de interesse porque sao usadas na medicina popular. Esses generos sao ricos em alcaloides pirrolizidinicos (AP), que sao as principais toxinas e apresentam efeitos pneumotoxicos, nefrotoxicos, cardiotoxicos, fetotoxicos, carcinogenicos, inflamacao, hemorragia e fibrose. A monocrotalina e o principal alcaloide pirrolizidinico encontrado nessas plantas e e ativamente oxidada in vivo pelo citocromo P450 no figado, formando intermediarios altamente reativos tipo pirrolicos que sao responsaveis pela ligacao cruzada do DNA-DNA e DNA-proteina. O presente trabalho teve como objetivo fazer um levantamento bibliografico via internet, utilizando bancos de dados, programas de pesquisa cientifica e pesquisa em livros relacionados, acerca da atividade farmacologica e do mecanismo de acao da monocrotalina extraida de plantas do genero Crotalaria, ressaltando desde os aspectos botânicos da planta, estrutura quimica dos alcaloides pirrolizidinicos, exemplos experimentais de toxicidade e provavel mecanismo de acao.

Oxidation of Pyrrole-2-carboxylates with o-Chloranil and Its Synthetic Application

t-Butyl 3,4-dialkyl-1H-pyrrole-2-carboxylates were oxidized with o-chloranil in the presence of MeOH to afford the corresponding 5-methoxypyrrolin-2-one derivatives. The resulting 5-methoxypyrrolin-2-one was reacted with various nucleophiles under acidic conditions to afford the functionalized pyrrolinone derivatives in good yields. Toward elucidation of the structure and function of the linear tetrapyrrole (bilin) chromophores in phytochromes, we have succeeded in synthesizing phytochromobilin (PΦB), phycocyanobilin (PCB), modified PCBs, biliverdin (BV) and its analogs including sterically locked derivatives in free acid forms by developing efficient methods for the preparation of each pyrrole ring and a new coupling reaction between them. In order to synthesize different types of locked chromophores, it was necessary to prepare various pyrrole and pyrrolinone derivatives bearing a wide variety of functional groups. In our previous syntheses, pyrrole rings with an electron withdrawing group were constructed by a modified Barton reaction starting from aldehydes, 1-nitroalkanes, and isonitrile compounds. The produced tosyland ester-substituted pyrroles were converted into Aor D-ring and Bor C-ring, respectively. It would be ideal for the synthesis of the locked bilin chromophores if the various types of pyrroles and the related pyrrolinones could be available from a common pyrrole by a simple manipulation. Recently we have developed a regioselective oxidation of the α-position of the C-4 substituents on t-butyl pyrrole-2-carboxylates with DDQ and the subsequent substitution reaction via azafulvene intermediates (Scheme 1). Herein we describe an oxidation of t-butyl pyrrole-2-carboxylates with o-chloranil and its application toward the synthesis of various types of functionalized pyrrolinone derivatives. N H CO2 tBu DDQ AcOH N H CO2 tBu R OAc R Nu base N H CO2 tBu Nu

GC-MS investigation and toxicological evaluation of alkaloids from Leptadenia pyrotechnica

GC-MS analysis of isolated alkaloids from aerial parts of Leptadenia pyrotechnica (Forsk.) Decne (Asclepiadaceae) was performed. Twenty-four alkaloids and six simple amines were detected for the first time in this plant. Almost all of the alkaloids belonged to pyridine, pyrrole, pyrazine, and indole types. The acute LC50 of the total alkaloids and alcohol extracts estimated by means of brine shrimp toxicity test were 63.09 and 11.89 ppm, respectively. The antitumor activities of these extracts, using potato disc screen, showed good activity represented by −33.6% and −49.3%, respectively.

A combined QCM and XPS investigation of asphaltene adsorption on metal surfaces

To investigate asphaltene–metal interactions, a combined quartz crystal microbalance (QCM) and X-ray photoelectron spectroscopy (XPS) study of asphaltene adsorption on a gold surface was conducted. Adsorption experiments were conducted at 25 °C with solutions of asphaltenes in toluene at concentrations ranging from 50 to 1500 ppm. QCM measurements yielded information on the kinetics of adsorption and further assessment of the data allowed the estimation of equilibrium adsorption levels. XPS analysis of adsorbed and bulk asphaltene demonstrated the presence of carboxylic, thiophenic, sulfide, pyridinic and pyrrolic type functional groups. The intensity of the main carbon (C–H) peak was related to surface coverage of adsorbed asphaltene as a function of asphaltene concentration by a simple mathematical model. The mass adsorption data from the QCM experiments also allowed estimation of the surface coverage, which was compared to those from XPS analyses. Surface coverage estimates as a function of asphaltene concentration could be described by a Langmuir (type-I) isotherm. The free energy of asphaltene adsorption was estimated to be − 26.8 ± 0.1 and − 27.3 ± 0.1 kJ / mol from QCM and XPS data, respectively assuming asphaltene molar mass of 750 g/gmol. QCM and XPS data was also analyzed to estimate adsorbed layer thickness after accounting for surface coverage. The thickness of the adsorbed asphaltene estimated from both XPS and QCM data analyses ranged from 6–8 nm over the entire range of adsorption concentrations investigated.

An x-ray absorption and photoemission study of the electronic structure of Ni porphyrinsand Ni N-confused porphyrin

Investigations of chemical bonding and electronic structure features for polycrystalline(porphyrinato)nickel (II) (NiP, the simplest Ni porphyrin), (5,10,15,20-tetraphenylporphyrinato)nickel(II) (NiTPP) and (2-aza-21-carba-5,10,15,20-tetraphenylporphyrinato)nickel(II) (N-confused NiTPP, NiNCTPP) have been performed by means ofhigh-resolution soft x-ray absorption and x-ray photoemission spectroscopy. The Ni2p3/2 x-ray absorptionspectra show strong π-back-bonding in these compounds leading to a high-energy shift (1.2 eVfor the NiP and NiTPP) of the entire absorption structure compared toNi metal. It has been found that the main absorption line of the Ni2p3/2 spectrum of the NiNCTPP is shifted by an additional 0.5 eV to higher energies incomparison with those for other nickel porphyrins. This shift is evidence of strongerback-donation (metal-to-ligand charge transfer) and a smaller effective number of3d electrons on the central Ni atom in the NiNCTPP as compared to other Niporphyrins. The confused N atom in the NiNCTPP is of pyrrolic type (protonatednitrogen), which was confirmed by the N 1s absorption and core-level photoemissionspectra.

A new acenaphthenequinone-based calix[4]pyrrole: Synthesis, structure and anion binding study

A new calix[4]pyrrole type anion receptor ( 1) containing two anti-symmetrically meso-situated acenaphthenequinone moieties has been constructed by a “one-pot” facile synthesis. The crystal structures of 1 and 1·F − complex were characterized by X-ray crystallography. The crystal of 1·F − complex witnessed that a C H group from the acenaphthenequinone participated in anion binding through C H…F hydrogen bond which was also conformed in solution by 1H NMR titration in CD 2Cl 2. The anion binding property of 1 was studied in CH 2Cl 2 using UV–vis spectrometry and the results reflected that it bound selectively with F − and Cl − ions.

Structure and surface elemental state analysis of polyimide resin film after carbonization and graphitization

AbstractThe carbon materials prepared from polyimide (PI) resin film were investigated by TG‐DTG, X‐ray powder diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS) analysis. TG‐DTG study revealed that the weight loss of PI resin film during carbonization occurred in three stages, and the most serious changes occurred at 605.5°C. XRD results indicated that a disorder structure occurred after the carbonization at 600°C and graphite crystallite appeared gradually with increasing the temperature. And PI resin film still presented some characteristics of nongraphitizing carbon, after graphitizing at 2600°C. XPS analysis identified that pyrrole type nitrogen was a main component of surface nitrogen atoms after carbonization. When the temperature reached 2600°C, nitrogen atoms disappeared totally; the reason why oxygen atoms still existed in the material at so high temperature was our subject of interesting matter in the later study. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Unambiguous assignment of trifluoromethylpyrazole regioisomers by 19F–15N correlation spectroscopy

Analysis of the 19F chemical shifts of trifluoromethylpyrazole regioisomers has shown that while chemical shift is in general a reliable predictor of regiochemistry in this series, there is a narrow chemical shift range in which the two isomers overlap and the regiochemistry cannot be assigned with certainty. We have examined the usage of 19F--15N correlation spectroscopy as a method to provide a second unambiguous confirmation of regiochemistry of 3- and 5-trifluoromethylpyrazole regioisomers. In the case of 3-trifluoromethyl analogs, one expects a three-bond coupling to the pyridine type nitrogen (N-2). In the case of the 5-trifluoromethyl pyrazole the situation is exactly reversed, with the fluorines of the trifluoromethyl moiety being 3-bonds from the pyrrole type nitrogen (N-1). We have observed that 3-trifluromethyl analogs follow the expected pattern of readily observable 3-bond coupling. However, 19F--15N couplings in 5-trifluromethyl analogs do not follow the normal pattern of 3-bond coupling. Using this information we have been able to develop unambiguous methods to distinguish the isomers.

Corrosion Inhibitor Fe Interactions: A Study Combining Surface Science and Electrochemistry

The difference in corrosion inhibition behavior of imidazole deposited on iron by two different methods has been examined using Electrochemical Impedance Spectroscopy (EIS) and X-ray Photoelectron Spectroscopy (XPS). Adding imidazole directly into the aqueous corrosive medium has been observed to provide greater protection against corrosion, in comparison to the direct deposition of the inhibitor onto the metal surface prior to exposure to the corrosive solution. Analysis of the AC impedance spectra revealed that the value of the polarization resistance (Rp) in the case of imidazole addition to the corrosive medium was an order of magnitude higher than in the predeposited case. Results of XPS investigations suggested that in the former case, the imidazole reacts through the pyrrole type nitrogen with the aromatic ring more parallel to the metal surface. In the latter situation pyridine type nitrogen-iron interaction predominates with the imidazole ring more normal to the surface.

Reactions of Substituted Furan-2-carboxaldehydes and Furo[b]pyrrole Type Aldehydes with Benzothiazolium Salts

A series of new push-pull compounds were synthesised by reaction of 5-aryl- furan-2-carboxaldehydes and furo[b]pyrrole type aldehydes with benzothiazolium salts. These new condensation products represent highly conjugated systems that have potential biological activity. The reaction of furo[b]pyrrole type aldehydes with benzothiazolium salts give potential precursors of cyanine dyes.

Reaction of Substituted Furan-2-carboxaldehydes and Furo[b]pyrrole Type Aldehydes with Hippuric Acid

4-Heteroarylidene-2-phenyl-1,3-oxazol-5(4H)-ones were prepared by reactions of hippuric acid with substituted furan-2-carboxaldehydes or furo[b]pyrrole type aldehydes. The reactivity of various furan-2-carboxaldehyde derivatives in this reaction is discussed. The effect of microwave irradiation on some condensation reactions was compared with "classical" conditions. The results show that microwave irradiation shortens the reaction times while affording comparable yields. Elementary analysis, UV, IR and 1D NMR proved the structure of new synthesised compounds. 2D NMR spectroscopic measurements confirmed that the configuration at the carbon-carbon double bond corresponds to the pure E isomers of the products.

Molecular Ionics of Anion Receptor Molecules: A Microcalorimetric Study

The coordination of divalent and monovalent inorganic anions to synthetic polyammonium receptors is investigated in aqueous solution around neutral pH by titration calorimetry and NMR spectroscopy. High-affinity 1:1 complexes are formed by a pyrrole type cryptand (1) with sulfate and phosphate, characterized by association constants of almost 107 M-1. Affinities close to 105 M-1 are found for polyazacryptands (3 and 4) exhibiting F-/Cl- selectivity. The binding affinities and the anion selectivities are mainly caused by the charges of ligands and anions, which is discussed on the basis of simple calculations of the electrostatic contribution to the anion/receptor interactions. The binding of all investigated anions is exothermic at 298.2 K. The contribution of the large negative ΔH values to the free energy of anion binding of the pyrrole type ligand is partially compensated by marked negative ΔS values. These unfavorable entropic contributions are attributed to the additional inclusion of water molecules in the anion/receptor complexes.

A theoretical search on metal–ligand interaction mechanism in corrosion of some imidazolidine derivatives

The interaction mechanism of some imidazolidine derivatives with metallic Zn in gas phase, using semiempirical methods, was studied at elevated temperature and the obtained data were used to search a possible correlation between the computed and experimental results obtained for Fe in the literature. It was concluded that the interaction between the metallic Zn and the protonated imidazolidine molecules occurs as physical adsorption via electrostatic interaction between Zn surface which covered by negatively charged Cl − ions in acidic media (i.e. 0.1N HCl). However, chemical adsorption may also take place via two possible ways by forming coordinate covalent bond; one possible way is giving one pair of electrons (i.e. lone pair) from pyrrole type nitrogen atom to the Zn and the second possible way is giving one pair of electron (i.e. lone pair) from pyridine type nitrogen atom which already released the proton as hydrogen gas at the cathode becoming a neutral sp 2 hybridized nitrogen atom.