1588-89-2Relevant articles and documents
Cyclometallated compounds V. Double cyclopalladation of diphenyl pyrazines and related ligands
Steel, Peter J.,Caygill, Graham B.
, p. 359 - 373 (1990)
2,3-Diphenylpyrazine and four structurally related ligands have each been singly and doubly cyclopalladated and the products characterised by 1H and 13C NMR studies of their acetylacetonate complexes.The structure of a doubly cyclometallated Pd(acac) comp
N-heterocycles as corrosion inhibitors for mild steel in acid medium
Saranya, Jagadeesan,Sowmiya, Murugaiyan,Sounthari, Palanisamy,Parameswari, Kandhasamy,Chitra, Subramanian,Senthilkumar, Kittusamy
, p. 42 - 52 (2016)
The corrosion behavior of mild steel in 1 M H2SO4 was studied using 2,3-diphenylpyrazine (DP), 2,3-di(furan-2-yl)pyrazine (FP) and 2,3-di(furan-2-yl)quinoxaline (FQ) as inhibitors using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) methods were utilized for surface characterization. The results showed that the three inhibitors possess excellent inhibition effect toward mild steel corrosion. The inhibitor molecules are adsorbed on the mild steel surface, blocking the reactive sites available for acid attack. Adsorption of the inhibitor was found to obey Langmuir isotherm. Electronic structure calculations were used to study the inhibition efficiency of the inhibitor molecules on Fe (100) surface. The calculated results are in agreement with the experimental findings.
Porous carbons-derived from vegetal biomass in the synthesis of quinoxalines. Mechanistic insights
Godino-Ojer,Blazquez-García,Matos,Bernardo,Fonseca,Pérez Mayoral
, p. 90 - 99 (2019/06/24)
We report herein for the first-time acid biomass-derived carbons from vegetal biomass, with high developed porosity, prepared through integrating method comprising pyrolysis and surface phosphonation, able to efficiently catalyze the synthesis of quinoxalines from 1,2-diamines and α-hydroxi ketones, under aerobic conditions. The obtained results indicate that the reaction is mainly driven by a combination of acid function strength and textural properties in terms of conversion and selectivity. Furthermore, our experimental and theoretical observations suggest that the preferred reaction pathway for this transformation, in the presence of the investigated acid carbon catalysts, involves cascade reactions including imination reaction between reactants, successive imine-enamine and keto-enol tautomerisms, heterocyclization followed by dehydration, and aromatization. While the acid sites seem to be a relevant role in each reaction step, the system formed by activated carbon and molecular oxygen could be behind the last oxidative reaction to give the corresponding nitrogen heterocycles.
Electrochemical oxidation synergizing with Br?nsted-acid catalysis leads to [4 + 2] annulation for the synthesis of pyrazines
Liu, Kun,Song, Chunlan,Wu, Jiarong,Deng, Yuqi,Tang, Shan,Lei, Aiwen
supporting information, p. 765 - 769 (2019/02/27)
An electrochemical dehydrogenative [4 + 2] annulation for the synthesis of pyrazines has been developed under undivided electrolytic conditions. In this protocol, neither external chemical oxidants nor transition-metal catalysts are needed, and a wide range of substituted pyrazines could be obtained from simple ketones and diamines in high efficiencies. Of note is that this electrolysis could also be extended for the construction of biheteroarenes and large π systems with good yields.
Gold-Catalyzed Oxidation of Internal Alkynes into Benzils and its Application for One-Pot Synthesis of Five-, Six-, and Seven-Membered Azaheterocycles
Dubovtsev, Alexey Yu.,Dar'in, Dmitry V.,Krasavin, Mikhail,Kukushkin, Vadim Yu.
, p. 1856 - 1864 (2019/02/19)
Internal alkynes have been shown to undergo oxidation to substituted benzils (1,2-diarylethane-1,2-diones) by α-picoline N-oxide in the presence of Ph3PAuNТf2 (5 mol-%). In addition to the unsubstituted benzil, the method allows preparing, under markedly mild conditions (50 °C in chlorobenzene), various non-symmetrical products, including heteroaromatic versions thereof which are much more difficult to obtain otherwise. This gold(I)-catalyzed transformation was integrated into one-pot reaction sequence delivering a range of 5- to 7-membered ring systems (imidazoles, quinoxalines, 1,2,4-triazines, pyrazines, and 1,4-diazepines), thus linking these important heterocyclic motifs to the internal alkyne reagent space.
Silica gel an efficient catalyst for one-pot synthesis of pyrazines from ethylenediamine and 1, 2-diketones and their analogs
Chakraborty, Rakesh Ranjan,Singha, Rabindranath,Ghosh, Pranab
, p. 373 - 378 (2018/09/29)
A straightforward one-pot synthesis of pyrazines from ethylenediamine and 1, 2-diketones/ α-hydroxy ketone/α-bromo ketone under solvent-free conditions at room temperature is described. This environmentally benign process has the edge on previous methods in respect of workup procedure, ease and cost of reaction, and use and generation of hazardous substances. The catalyst is recovered, characterized, and proved to be recyclable for successive four runs examined with appreciable conversions.
Clean and green approach for one-pot synthesis of pyrazines from Eth-ylenediamine and 1,2-diketone or its analogues under neat reaction condition
Ghosh, Pranab,Chakraborty, Rakesh Ranjan
, p. 566 - 570 (2017/09/29)
Background: Compounds having N-heterocyclic moieties are of huge importance in the field of agrochemical, pharmaceutical, biological, fragrances, etc. Due to a lot of applications associated with pyrazine moieties, their synthesis has always been important for organic chemists. Method: Surfeit synthetic methodologies are documented in literature. Most of the methodologies used expensive solvents, harmful metal catalyst and all suffer from rigorous work-up procedures. An efficient, environmentally benign methodology, needs to be developed. We mixed ethylenediamine (2mmol) with 1, 2-diketone(1mmol), later, α-hydroxy ketone and α-bromo ketone on magnetic stirrer at room temperature under neat reaction condition for 5 to 10 hrs. Results: After purification by column chromatography using silica gel(60-120 mesh) and pet-ether, et-hylacetate mixture as eluent, we achieved pyrazine derivatives from moderate to high yield. Conclusio n: Efficient and clean procedure for one-pot preparation of pyrazines from ethylenediamine and 1, 2-diketones or with α-hydroxy ketone or with α-bromo ketone has been carried out under neat reaction condition at room temperature. Environmentally benign process furnishing moderate to excellent yields of the product and simple work-up giving pure products are special features of this reaction.
Increasing the triplet lifetime and extending the ground-state absorption of biscyclometalated Ir(III) complexes for reverse saturable absorption and photodynamic therapy applications
Wang, Chengzhe,Lystrom, Levi,Yin, Huimin,Hetu, Marc,Kilina, Svetlana,McFarland, Sherri A.,Sun, Wenfang
supporting information, p. 16366 - 16378 (2016/10/31)
The synthesis, photophysics, reverse saturable absorption, and photodynamic therapeutic effect of six cationic biscyclometalated Ir(iii) complexes (1-6) with extended π-conjugation on the diimine ligand and/or the cyclometalating ligands are reported in this paper. All complexes possess ligand-localized 1π,π? absorption bands below 400 nm and charge-transfer absorption bands above 400 nm. They are all emissive in the 500-800 nm range in deoxygenated solutions at room temperature. All complexes exhibit strong and broad triplet excited-state absorption at 430-800 nm, and thus strong reverse saturable absorption for ns laser pulses at 532 nm. Complexes 1-4 are strong reverse saturable absorbers at 532 nm, while complex 6 could be a good candidate as a broadband reverse saturable absorber at 500-850 nm. The degree of π-conjugation of the diimine ligand mainly influences the 1π,π? transitions in their UV-vis absorption spectra, while the degree of π-conjugation of the cyclometalating ligand primarily affects the nature and energies of the lowest singlet and emitting triplet excited states. However, the lowest-energy triplet excited states for complexes 3-6 that contain the same benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine (dppn) diimine ligand but different cyclometalating ligands remain the same as the dppn ligand-localized 3π,π? state, which gives rise to the long-lived, strong excited-state absorption in the visible to the near-IR region. All of the complexes exhibit a photodynamic therapeutic effect upon visible or red light activation, with complex 6 possessing the largest phototherapeutic index reported to date (>400) for an Ir(iii) complex. Interactions with biological targets such as DNA suggest that a novel mechanism of action may be at play for the photosensitizing effect. These Ir(iii) complexes also produce strong intracellular luminescence that highlights their potential as theranostic agents.
Method for manufacturing triarylpyrazine derivative
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Paragraph 0141-0142, (2016/11/17)
A novel synthesis method of a triarylpyrazine derivative, in particular, a manufacturing method by which a triarylpyrazine derivative, in specific, a 2,3,5-triarylpyrazine derivative in which an aryl group at a 5-position includes a substituent having an electron-withdrawing property can be synthesized with high yield as compared to a conventional method is provided. By using a synthesis method in which a mixture including a 1-aryl-2-(methylsulfinyl)ethanone derivative, meso-1,2-diarylethylenediamine, and a dehydrogenation agent is irradiated with a microwave to be reacted, the above object is achieved.
Synthesis of Chiral Piperazines via Hydrogenation of Pyrazines Activated by Alkyl Halides
Huang, Wen-Xue,Liu, Lian-Jin,Wu, Bo,Feng, Guang-Shou,Wang, Baomin,Zhou, Yong-Gui
supporting information, p. 3082 - 3085 (2016/07/13)
A facile method has been developed for the synthesis of chiral piperazines through Ir-catalyzed hydrogenation of pyrazines activated by alkyl halides, giving a wide range of chiral piperazines including 3-substituted as well as 2,3- and 3,5-disubstituted
