Nitrogen-containing Heteroaromatics Research Articles

Optimizing extractants selection for efficient separation of phenols and nitrogen-containing heteroaromatics using hydrogen bond interaction strategies

Optimizing extractants selection for efficient separation of phenols and nitrogen-containing heteroaromatics using hydrogen bond interaction strategies

Ionic liquid/boronic acid system enabled deuteration with D2O

The development of transition-metal free systems for multi-sites deuteration is important for the preparation of deuterium-labeled drugs and intermediates. We reported that ionic liquid [bmim]PF6 was able to promote highly efficient deuterodeborylation of boronic acids with D2O. The ionic liquid/boronic acid system was successfully applied to the selective H/D exchange at various sp2/sp3 CH positions. Moreover, unusual nucleophilic behaviors of nitrogen-containing heteroaromatics in ionic liquid were observed.

2-Imidazole as a Substitute for the Electrophilic Group Gives Highly Potent Prolyl Oligopeptidase Inhibitors.

Different five-membered nitrogen-containing heteroaromatics in the position of the typical electrophilic group in prolyl oligopeptidase (PREP) inhibitors were investigated and compared to tetrazole. The 2-imidazoles were highly potent inhibitors of the proteolytic activity. The binding mode for the basic imidazole was studied by molecular docking as it was expected to differ from the acidic tetrazole. A new putative noncovalent binding mode with an interaction to His680 was found for the 2-imidazoles. Inhibition of the proteolytic activity did not correlate with the modulating effect on protein–protein-interaction-derived functions of PREP (i.e., dimerization of alpha-synuclein and autophagy). Among the highly potent PREP inhibiting 2-imidazoles, only one was also a potent modulator of PREP-catalyzed alpha-synuclein dimerization, indicating that the linker length on the opposite side of the molecule from the five-membered heteroaromatic is critical for the disconnected structure–activity relationships.

Copper-catalyzed versatile C(sp3)–H arylation: synthetic scope and regioselectivity investigations

A mild and practical protocol is developed for the synthesis of functionalized nitrogen-containing heteroaromatics via radical C(sp2)–H or C(sp2)–halogen alkylation.

Electrochemical Intramolecular C-H Amination of Aromatic Compounds

C-H amination is a straightforward method to synthesize nitrogen-containing organic compounds. Electrochemical oxidation serves as a powerful method to functionalize C-H bonds of aromatic compounds. However, it often suffers from overoxidation when the product is easily oxidized compared to the starting material. Therefore, electrooxidative C-H amination of aromatic compounds has been difficult so far. To solve the problem, we have developed a new approach to the electrochemical intermolecular C-H amination of aromatic compounds via N-arylpyridinium ions, which can be converted to aromatic primary amines by a subsequent chemical reaction. In this paper we report that the method can also be applied to the intramolecular C-H amination of aromatic compounds to give nitrogen-containing heteroaromatics. Benzoxazoles and benzothiazoles were successfully synthesized from phenols and thiophenols, respectively. The intermediacy of the electrooxidatively inactive cationic intermediates which avoid overoxidation is responsible for the success of the transformation.

ChemInform Abstract: Introduction of Ether Groups onto Electron‐Deficient Nitrogen‐Containing Heteroaromatics Using Radical Chemistry under Transition‐Metal‐Free Conditions.

Electron-deficient nitrogen-containing heteroaromatics, such as quinoline, isoquinoline, and pyridine, were treated with benzoyl peroxide in dioxane, tetrahydropyran, tetrahydrofuran, diethyl ether, and dipropyl ether at 80 °C to form alkylated nitrogen-containing heteroaromatics in good yields under transition-metal-free conditions. This method was successfully applied to the preparation of lariat aza-crown ethers using 18-crown-6 or 15-crown-5 with quinoline and isoquinoline in the presence of benzoyl peroxide in good yields under irradiation conditions with a Hg lamp.

Observation of Surface-Bound Negatively Charged Hydride and Hydroxide on GaP(110) in H2O Environments

Surface-bound species on GaP(110) formed upon interaction with water were investigated through experiment and theory. These studies are motivated by and discussed in the context of electrocatalytic and photoelectrocatalytic schemes for solar fuel production, including especially observations of selective CO2 reduction to methanol in acidified aqueous solutions of CO2 and nitrogen-containing heteroaromatics. Experimentally, surface-bound species over 10 orders of magnitude of pressure were spectroscopically identified in situ using synchrotron-based ambient pressure photoelectron spectroscopy. Ga 3d and O 1s core-level spectra indicate that the interaction of GaP(110) with H2O induces formation of a partially dissociated adlayer, characterized by the presence of both Ga–OH and molecular H2O species. Measurements of the P 2p core level indicate formation of a negatively charged hydride that irreversibly bonds to surface P in vacuum. The surface densities of the hydroxide and hydride species increase with in...

Regiochemistry in Cobalt-Mediated Intermolecular Pauson–Khand Reactions of Unsymmetrical Internal Heteroaromatic Alkynes with Norbornene

The intermolecular Pauson-Khand (PK) reactions of sterically comparable (2-phenylethynyl)heteroaromatic compounds with norbornene, mediated by Co(2)(CO)(8) to give cyclopentenone products, were examined in this study. A synthetic protocol utilizing focused-microwave dielectric heating proved indispensable in the efficient synthesis of the PK cyclopentenone products. "π-Deficient" heteroaromatic substrates, e.g., 2-pyrones, and some "π-excessive" heteroaromatics such as 2- and 3-thiophene and 2-furan favor the β-position in the newly formed cyclopentenone ring. Other π-excessive heteroaromatics such as 2-pyrrole or 2-indole favor the α-position. A π-excessive 3-indole derivative gave a nearly equal mixture of regioisomers. The position of the nitrogen in pyridyl-containing alkyne substrates also affects the regiochemical outcome of the PK reaction. A 2-pyridyl alkyne, possessing a proximal nitrogen, influences the regioselectivity relative to a 4-pyridyl variant quite dramatically, favoring the β-position in the newly formed cyclopentenone ring. A 2-pyrimidylalkyne exhibits similar behavior to the 2-pyridylalkyne. Compounds that do not participate in PK reactions with norbornene include (2-phenylethynyl)imidazoles and the related benzimidazoles, which promote rapid decomposition of the in situ generated (μ(2)-alkyne)Co(2)(CO)(6) complexes. This stands in contrast with other nitrogen-containing heteroaromatics, e.g., pyrrole-, indole-, and pyrimidine-derived compounds, which effectively undergo PK reactions. Overall, the type of heteroaromatic group dramatically influences PK regioselectivity, which can in part be explained by rationalization of the current reaction mechanism, but not fully.

Desulfurization and denitrogenation of gasoline and diesel fuels by means of ionic liquids

Ionic liquids can extract mono- and poly-aromatic sulfur and nitrogen compounds from gasoline and diesel and they perform better than conventional solvents. The extraction capacity of several ionic liquids for these heterocyclic compounds is determined and compared to the extraction capacity for aromatic hydrocarbons. Furthermore, the experimental results obtained are evaluated in view of the results reported in literature. It is shown that the ionic liquids investigated in this work are able to extract sulfur as well as nitrogen-containing aromatics in preference to aromatic hydrocarbons. Moreover, the ionic liquids [3-mebupy]N(CN)2, [4-mebupy]N(CN)2 and [bmim]C(CN)3 are superior to sulfolane, which has been used as a benchmark and also outperform the ionic liquids reported in literature so far. Finally, it has been shown that nitrogen-containing hetero-aromatics are significantly better extracted than sulfur-containing hetero-aromatics.

Direct synthesis of H-aryl and H-heteroarylphosphinic esters via palladium-catalyzed cross-coupling of alkylphosphinates

Aryl, heteroaryl, and benzylic electrophiles can be coupled to in situ-generated alkylphosphinates (ROP(O)H 2) in moderate to good yields using palladium catalysis. For the first time, electrophiles other than simple aryl iodides can be employed in an experimentally straightforward, one-pot reaction. The direct formation of H-phosphinic esters avoids the separate esterification of H-phosphinic (phosphonous) acids and is particularly useful in the case of nitrogen-containing heteroaromatics. The reaction significantly expands the scope of related palladium-catalyzed phosphorus-carbon bond-forming reactions. To cite this article: Z. Huang et al., C. R. Chimie 7 (2004).

An EPR study of the reaction of tetrabutylammonium borohydride with N-Heterocycles

The reactions between tetrabutylammonium borohydride and a series of nitrogen-containing heteroaromatics bases have been investigated by electron paramagnetic resonance (EPR) spectroscopy. The radical anions of the N-heterocycles, formed by a single electron-transfer process have been observed with substrates having reduction potentials higher than - 1.2 V vs. SCE. With less reducible bases, the radical anions of the adducts formed by complexation by one or two borane units of the nitrogen atoms of the base were observed under photolytic conditions. This is because the complexed N-heterocycles have larger electron affinities than the starting base.

Characterization of coal tars produced under different carbonization conditions by FT-i.r. spectroscopy and extrography

Coal tars produced by carbonization of wet charges of one coal blend on industrial and semi-industrial scales with different mean flue temperatures and from a preheated charge of the same blend were studied. These tars were characterized by FT-i.r. and 1H n.m.r. spectroscopy in addition to the standard analytical methods. They were also separated by extrography into fractions differing in chemical functionality, which were examined by FT-i.r. spectroscopy and g.c.-m.s., Differences were mainly observed in the proportions of polynuclear aromatic hydrocarbons and nitrogen-containing heteroaromatics. The information can be used as an indicator of the severity of thermal cracking during tar formation in a coke oven.

Phase transfer catalysed reductive acylation of nitrogen-containing heteroaromatics with acetylcobalt tetracarbonyl

Phase transfer catalysed reductive ring-cleavage acylation of isoxazoles or isothiazoles with acetylcobalt tetracarbonyl gives N-acylated 1-amino-2-alkene-3-ones or thiones. Under the same conditions phthalazine, quinoline and isoquinoline react with acetylcobalt tetracarbonyl to give N-acylated dimers. The reactivity of several other nitrogen-containing heterocycles was also investigated.

Decomposition and stabilization of drugs. XIII. Structure and stability of aminoalkylesters (author's transl)

The 2-diethylaminoethylesters of heteroaromatic acid, such as 2-furoic acid (I), 2-thiophenecarboxylic acid (II), nicotinic acid (III) and quinaldic acid (IV) were synthesized and the rate of their hydrolysis was measured in an aqueous buffered solution. The same experiments were performed with 2-diethylaminoethylesters of benzoic acid (V) and 1-naphthoic acid (VI) for comparison. Esters of nitrogen-containing heteroaromatics, such as III and IV, differed in the pH-rate profile and were unstable compared with aromatic esters such as V and VI. The half-life of III and IV was calculated to be about 54.7 and 18.0 days, respectively, in an aqueous solution of pH 5.0 and at 25°.