Addition Of Pyrrole Research Articles

Core-shell Fe3Al@polypyrrole composites with tunable shell thickness and enhanced microwave absorption performance

Nowadays, core-shell structures have attracted considerable attention as microwave absorbers (MAs) due to the synergistic effect between dielectric and magnetic loss. Herein, core-shell Fe3Al@polypyrrole (Fe3Al@PPy) composites were successfully fabricated by the thermit reaction and chemical oxidation polymerization method with the assistance of ammonium persulfate and p-toluene sulfonic acid. Due to the regulation of the impedance matching by the electromagnetic coupling and core-shell structure, the Fe3Al@PPy composites showed enhanced electromagnetic wave (EMW) absorption performance compared with the pure Fe3Al. Furthermore, the thickness of the PPy shell increased from 0.23 µm to 1.50 µm as the addition of pyrrole (Py) increased from 0.25 mL to 1.0 mL. Meanwhile, the core-shell Fe3Al@PPy composites exhibited the optimal wave absorption performance when the PPy shell thickness was 0.80 µm, and the reflection loss (RL) could reach − 40.53 dB with the thickness of 2.0 mm at 13.3 GHz. This work provides a new idea for the design of large-scale electromagnetic (EM) coupled MAs with core-shell structures.

A Stabilized Assisted Method for the Synthesis of Fe-N-C Catalysts for the Oxygen Reduction Reaction

Iron-nitrogen-carbon graphitic (Fe-N-C), a noble metal-free catalyst holds a lot of promise to substitute platinum (Pt) as an efficient catalyst in the oxygen reduction reaction (ORR). However, the synthesis process and the stabilization of single atoms that tend to aggregate, without jeopardizing the catalytic activity remain challenging. Here we demonstrate a stabilized assisted method for the preparation of Fe-N-C electrocatalyst by using graphitic carbon nitride (g-C3N4) nanosheet as a template. Fe ions are absorbed on the surface of g-C3N4 and imprisoned after the addition of pyrrole, preventing Fe migration that may result in nanoparticles. During the pyrolysis, Fe atoms coordinated with N provided by g-C3N4 and pyrrole on graphitic carbon to form Fe-N-C with a metal loading of 5.4 wt%. Moreover, FeNx species were introduced in the graphitic carbon, where the coexistence of micro and mesopores were favorable to offer a larger density of active sites compared to Fe/NP without pyrrole. Fe-N-C demonstrated a good electrocatalytic performance with a half-wave potential (E 1/2) of 0.82 V (vs reversible hydrogen electrode (RHE)) higher than Fe/NP (0.76 V) and close to Pt/C, with a superior long stability of 85% in alkaline media after 40000 s.

Continuous-porous N-doped carbon network as high-performance electrode for lithium-ion batteries

Hierarchical porous N-doped carbon (NPC) is prepared by pyrolysis of poly(methyl methacrylate) (PMMA) particles decorated by graphene oxide (GO) and polypyrrole (PPy) as precursors and used as anode for lithium-ion batteries. The composite precursors with different diameter and composition (PMMA/GO/PPy-A and B) were conveniently prepared by dispersion polymerization of methyl methacrylate in the presence of graphene oxide as stabilizer in aqueous medium, followed by addition of pyrrole and its oxidative polymerization. After pyrolysis, the resulting NPC composites with hierarchically structured macro- and mesopores exhibit high surface area (289–398 m2/g) and different N-doping levels (7.46 and 4.22 wt% of nitrogen content). The NPC with the highest N-doping level (7.46 wt%) shows high reversible capacities of 831 mAh/g at 74.4 mA/g (C/5) after 50 cycles and excellent rate performances.

Acylation of Pyrroles and their Free (N‐H)‐Derivatives via Palladium‐Catalyzed Carbopalladation of Nitriles

AbstractAn efficient regioselective synthesis of 2‐acylpyrroles via palladium‐catalyzed addition of pyrroles with benzonitriles and subsequent hydrolysis is developed. The direct acylation reaction of protected as well as (NH)‐free pyrroles proceeded smoothly to afford 2‐acylpyrrole scaffolds of high biological interest.magnified image

Access to pyrrole-based heterocyclic compounds via addition of pyrrole to C=C and C=N bonds

Abstract A series of metal triflate-catalyzed addition reactions of pyrrole to C=C and C=N bonds have been investigated to access pyrrole-based heterocyclic compounds. The addition of pyrrole to different α,β-unsaturated compounds or N-tosyl imines afforded suitable structures for the construction of [5-5] bicyclic systems or porphyrins, respectively. Intramolecular cyclization reactions were applied for the synthesis of pyrrolizine derivatives. In the other reaction mode, intermolecular cyclization reactions gave A4- and trans-A2B2-meso-substituted porphyrins under mild reaction conditions with low scrambling.

Asymmetric Organocatalytic Michael Addition of Pyrroles to Enones by Cinchona Alkaloid-Derived Primary Amines

The enantioselective synthesis of 2-alkylated pyrroles via Michael addition of pyrroles to α,β-unsaturated ketones employing cinchona alkaloid-derived primary amines as organocatalysts is described. Good to excellent yields (78–99%) and good to very good enantioselectivities (75–93% ee) are obtained. With this protocol highly enantioenriched C-alkylated pyrroles can be synthesized easily, thus facilitating their possible application in medicinal chemistry.

ChemInform Abstract: Addition of Pyrroles onto Terminal Alkynes Catalyzed by a Dinuclear Ruthenium(II) Complex.

AbstractConditions are elaborated which allow the preparation of vinylpyrrole structures with a potential for further functionalization including the construction of dipyrromethane skeletons.

Addition of pyrroles onto terminal alkynes catalyzed by a dinuclear ruthenium (II) complex

The addition of pyrroles onto alkynes has been catalyzed by a dinuclear ruthenium complex, Ru2(CO)4(PPh3)2Br4, resulting in the formation of geminal 2-vinylpyrroles in high yields under mild conditions. Further functionalization with pyrroles or alkynes to afford dipyrrolmethanes or 2,5-bis(vinyl)pyrroles via the vinyl functional group can readily be achieved. A mechanism involving cationic ruthenium complexes was proposed based on the product regioselectivity, deuteration and infrared spectroscopic studies carried out on the catalytic process.

Enantioselective and Regioselective Indium-Catalyzed Addition of Pyrroles to Isatins

Enantioselective and Regioselective Indium-Catalyzed Addition of Pyrroles to Isatins

Reactions of Ruthenium-Allenylidene Complexes Tethering a Cyclopropyl Group

Two cyclopropyl allenylidene complexes [Ru]=C=C=C(R)(C(3)H(5)) ([Ru]=[RuCp(PPh(3))(2)], Cp=Cyclopentadienyl; R=thiophene (2a) and R=Ph (2b)) are prepared from the reactions of [Ru]Cl with the corresponding 1-cyclopropyl-2-propyn-1-ol in the presence of KPF(6). Thermal treatment, halide-anion addition, and palladium-catalyzed reactions of 2a and 2b all lead to a ring expansion of the cyclopropyl group, giving the vinylidene complexes 4a and 4b, respectively, each with a five-membered ring. This ring expansion proceeds by C-C bond formation between Cβ of the cumulative double bond and a methylene group of the cyclopropyl ring. In the reaction of 2a with pyrrole, consecutive formation of two C-C bonds, one between C-2 of pyrrole and Cγ of 2a and the other between C-3 of pyrrole and Cα, results in the formation of 6a. The reaction proceeds by addition of pyrrole and 1,3-proton shifts. The hydrogenation of 2a by NaBH(4) is carried out in different solvents. The cumulative double bonds are reduced regioselectively to give a mixture of 7a and 8a. Interestingly, use of different solvents leads to different ratios of 7a and 8a. Presence of a protic solvent like methanol in dichloromethane or chloroform solution increases the yield of 8a, thus revealing that both the rates of hydroboration and deboronation increase. The structures of two new complexes 4a and 6a have been firmly established by X-ray diffraction analysis.

ChemInform Abstract: A Combination of Water and Microwave Irradiation Promotes the Catalyst‐Free Addition of Pyrroles and Indoles to Nitroalkenes.

AbstractThe course of the high‐yielding reaction is independent of the kind of heterocycle and alkene substrates and can thus be applied to the preparation of natural products with pyrrole or indole moieties.

Microwave-Assisted Conjugate Addition of Pyrrole on Electron-Deficient Nitro-Olefins

Michael addition of pyrrole to β-nitrovinyl compounds were carried out using microwave methodology. Monosubstituted pyrroles were obtained selectively in a major amount. Formation of novel product obtained during one of the reactions was explained by the double addition to nitrostyrene.

Hafnium Chloride Catalyzed Conjugate Addition of Pyrrole, Pyrazole and Imidazole to α,β-Unsaturated Ketones

Pyrrole, pyrazole and imidazole undergo conjugate addition with α,β-unsaturated ketones in the presence of a catalytic amount of hafnium chloride at room temperature. Although the reaction of pyrrole gave 2,5-substituted C-adduct mainly, those of pyrazole and imidazole gave the corresponding N-adducts in excellent yields.

Conjugate addition of pyrroles to α,β-unsaturated ketones using copper bromide as a catalyst

Copper bromide was used as a catalyst for the addition of pyrroles to enones. When both the reactants were used in equimolar amounts, mono and dialkylated products were obtained. However, the use of excess enone furnished only dialkylated products. Thus, copper bromide was shown to be an efficient catalyst for the dialkylation of pyrroles.

Pyrrolate-Catalyzed Conjugate Addition of Pyrrole to Electron-Deficient Alkenes

The conjugate addition of pyrrole as a nitrogen nucleophile can be catalyzed by potassium pyrrolate in coordinating solvents or by lithium pyrrolate in the presence of coordinating ligands offering an efficient route to protected β-amino carbonyl compounds.

Surfactant-directed polypyrrole/CNT nanocables: synthesis, characterization, and enhanced electrical properties.

We describe here a new approach to the synthesis of size-controllable polypyrrole/carbon nanotube (CNT) nanocables by in situ chemical oxidative polymerization directed by the cationic surfactant cetyltrimethylammonium bromide (CTAB) or the nonionic surfactant polyethylene glycol mono-p-nonylphenyl ether (Opi-10). When carbon nanotubes are dispersed in a solution containing a certain concentration of CTAB or Opi-10, the surfactant molecules are adsorbed and arranged regularly on the CNT surfaces. On addition of pyrrole, some of the monomer is adsorbed at the surface of CNTs and/or wedged between the arranged CTAB or Opi-10 molecules. When ammonium persulfate (APS) is added, pyrrole is polymerized in situ at the surfaces of the CNTs (core layer) and ultimately forms the outer shell of the nanocables. Such polypyrrole/CNT nanocables show enhanced electrical properties; a negative temperature coefficient of resistance at 77-300 K and a negative magnetoresistance at 10-200 K were observed.

N‐ and C‐Vinylation of Pyrroles with Disubstituted Activated Acetylenes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

N-andC-Vinylation of Pyrroles with DisubstitutedActivated Acetylenes

Addition of pyrrole and 2-phenylpyrrole to 2-acyl- and 2-cyano-1-phenylacetylenes in the KOH-DMSO system affords chemo- and regioselectively N-adducts: 1-(2-acyl- and 1-(2-cyano-1-phenylethenyl)pyrroles in 32-89% yield. 4,5,6,7-Tetrahydroindole reacts with 2-cyano-1-phenylacetylene analogously. Unexpectedly, with 2-benzoyl-1-phenylacetylene, the reaction follows mainly the C-vinylation route to give (E,Z)-2-(2-benzoyl-1-phenylethenyl)-4,5,6,7-tetrahydroindole and cyclo-bis-adduct, 2-(2-benzoyl-1,3-diphenyl-1,4,5,6,7,8-hexahydrocyclopenta[b]indol-1-yl)-1-phenylethanone, a product of intramolecular cyclization of 2,3-di(2-benzoyl-1-phenylethenyl)-4,5,6,7-tetrahydroindole.

Induction of myxospores in Stigmatella aurantiaca (myxobacteria): analysis of inducer-inducer and inducer-inhibitor interactions by dose-response curves

Theories and methods developed in molecular pharmacology for drug receptor interactions were used to explain artificially induced myxospore formation. The correlation between inducer concentrations and the yield of myxospores, i.e. the experimentally obtained dose-response curves, were much steeper than expected for an interaction based on mass action law. We postulate that the interaction of an inducer with one of the different receptors of the bacterial cell causes the production of a common stimulus which programmes the cells to turn into myxospores, if a threshold value is reached. Simultaneous addition of inducers of the same or of different inducer groups showed synergistic interactions. Inducer concentrations that by themselves were not inducing gave maximum myxospore formation when combined. Addition of pyrrole, a specific inhibitor, caused a concentration-dependent parallel shift of the glycerol dose-response curve. Compounds, inducers or inhibitors, with identical receptor specificities competed for the common receptor according to their affinity. Interactions of inducers with different receptor specificities could be predicted from calculations with a mathematical model of functional synergism.

Organic additives for the electrolytes of rechargeable lithium batteries

The effects of some organic additives containing hetero-atoms on the charge—discharge characteristics of lithium have been investigated in propylene carbonate- or dimethylsulfoxide-based electrolytes. The addition of thiophene to propylene carbonate-based electrolytes improved the coulombic efficiency of the cycle, and the addition of pyrrole was effective for cycling in LiPF 6/dimethylsulfoxide. The effect of the addition of 2-methylfuran was significant in the solutions containing LiPF 6. The a.c. impedance behavior at the electrode/electrolyte interphase suggested that the addition effects are related to changes in the interphase structure.