Syntheses and reactions of some 2,3‐disubstituted pyrazine monoxides

Ohta, Akihiro; Masano, Sawako; Iwakura, Sachiko; Tamura, Akiko; Watahiki, Hiroko; Tsutsui, Mayumi; Akita, Yasuo; Watanabe, Tokuhiro; Kurihara, Teruo

doi:10.1002/jhet.5570190304

Cited by 28 publications

(19 citation statements)

References 13 publications

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“…All chemicals and solvents were purchased from commercial sources and used as received without further purification. The ligands dpp ( L1 ), 2,3–di(pyridin–2‐yl)quinoxaline ( L2 ), 2,3–di(pyridin–2‐yl)benzo[ g ]quinoxaline ( L3 ), dppi, and the Ir(III) dimer [Ir(dppi) 2 Cl] 2 , were prepared following the reported procedures. Column chromatography was carried out using silica gel (60 Å, 230–400 mesh) or Al 2 O 3 gel (activated, neutral).…”

Section: Methodsmentioning

confidence: 99%

Monocationic Iridium(III) Complexes with Far‐Red Charge‐Transfer Absorption and Near‐IR Emission: Synthesis, Photophysics, and Reverse Saturable Absorption

et al. 2019

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The synthesis, photophysics, and reverse saturable absorption (RSA) of three monocationic iridium(III) complexes (Ir1–Ir3) bearing diimine (N^N) ligand with different degrees of π‐conjugation are reported. Spectroscopic methods, including UV/Vis absorption, emission, and transient absorption spectroscopy, and density functional theory calculations were carried out to understand the nature of the singlet and triplet optical transitions and the influence of N^N ligand π‐conjugation on the photophysical properties of the complexes. All complexes possessed predominant ligand–centered, 1π,π* absorption bands at 280–420 nm and weak charge‐transfer absorption bands at 420–610 nm for Ir1, 420–680 nm for Ir2, and 420–730 nm for Ir3. The extended π‐conjugation of the N^N ligand red–shifted the charge‐transfer absorption bands and increased the molar extinction coefficients of all of the absorption bands. All complexes were emissive in the far‐red to the near‐infrared regions, with the emission energies gradually decreasing when the π‐conjugation of the N^N ligand increased. However, the emission lifetime of Ir3 increased when its emitting state energy decreased. This was caused by the different nature of the T1 state in Ir3, which was the predominant N^N ligand–localized 3π,π* state compared to the charge‐transfer T1 states in Ir1 and Ir2. The different parentage of the T1 state in Ir3 also gave rise to a much broader and stronger triplet excited‐state absorption in the 420–800 nm regions. The varied ground‐state and triplet excited‐state absorption characteristics led to a different strength of the reverse saturable absorption (RSA) for ns laser pulses at 532 nm, with the RSA strength following the trend of Ir3 > Ir1 ≥ Ir2. Complex Ir3 is particularly attractive for its potential as a broadband reverse saturable absorber in view of its broader ground‐ and excited‐state absorption in the regions of 420–730 nm and longer–lived triplet excited state.

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Section: Methodsmentioning

confidence: 99%

Monocationic Iridium(III) Complexes with Far‐Red Charge‐Transfer Absorption and Near‐IR Emission: Synthesis, Photophysics, and Reverse Saturable Absorption

et al. 2019

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“…After evaporation, the residue was purified by silica gel column chromatography (30% diethyl ether/n-hexane) to afford colorless oil. Kugel Role distillation at 205°C/2 Torr (158-160°C/22 Torr, 15) 140°C/7 Torr 16) ) afforded 102 mg (65%) of 2-methyl-3-pheny1pyrazine as colorless oil, which solidified in Ϫ20°C freezer, mp 31-32°C. 1 Deuterium Exchange Experiment All experiments were carried out in 20 mM concentration solutions of 3, 4 or 2-methyl-3-phenylpyrazine in 50% 5 , and were prepared under ice-water cooling.…”

Section: Methodsmentioning

confidence: 99%

Latent Enamine Functionality of 5-Methyl-2,3-dihydropyrazines

Ito

Hirano

Sugimoto

et al. 2010

CHEMICAL & PHARMACEUTICAL BULLETIN

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Dihydropyrazine derivatives (DHPs) derived from dimerization of amino sugars, such as glucosamine and mannosamine, spontaneously generate carbon-centered radicals and exhibit DNA strand-breaking activity, which may be related to the apoptotic activity of amino sugars.1,2) The DHP derivative 3,6-dihydropyrazine-2,5-dipropionic acid is formed by dimerization of 5-aminolevulic acid, which is accumulated in congenital and acquired hepatic porphyrias, such as acute intermittent porphyria, and might induce hepatocellular carcinoma.3) The dimerization of these aaminocarbonyl compounds proceeds via a non-enzymatic process under physiological conditions to afford 2,5-DHPs initially, and these might be isomerized to other types of DHPs as a consequence of resonance stabilization, and/or oxidized to pyrazines. However, the thermal and chemical instability of DHPs has made it difficult to investigate their chemical properties and biological functions in detail.Previously we reported the preparation of simple DHP derivatives such as 5,6-dimethyl-2,3-DHP (1) and 2,2,5,6-tetramethyl-2,3-DHP (2) by the reaction of diacetyl and ethylenediamines in diethyl ether according to Ishiguro's procedure (Chart 1).4) These methyl-substituted DHPs showed DNA strand-breaking activity with potency comparable to that of DHP formed from D-glucosamine.5) During mechanistic investigations, we found that compound 2 dimerized at room temperature without any catalyst.6,7) Semi-empirical PM3 molecular orbital (MO) calculation suggested the feasibility of tautomerization from 2 (diimine form) to 2exo (enamine form) during the dimerization reaction. Further, from a biological viewpoint, the reduction of Koopman's ionization potential value (IPϭϪE HOMO ) resulting from tautomerization of DHPs to the enamine form should be closely related to the DNA-damaging ability. 8) However, there is no evidence for the formation of an enamine moiety, such as 1exo and 2exo. In this study, we explored the possible formation of enamine tautomers of DHPs by means of theoretical and empirical methods. ExperimentalComputation The Spartan '06 and '08 for Windows software 9) with the density functional theory (DFT) B3LYP 10 /6-311ϩG** basis set was employed to estimate the global minimum energy of the optimized structures of compounds and transition states (TS). Zero point energy was not corrected. The obtained TS geometry was evaluated by means of vibrational frequency analysis and intrinsic reaction coordinate (IRC) calculation. The solvation effect of water was approximated by way of the SM8 model 11 at the DFT B3LYP/6-31G* basis set level, because the SM8 model did not cover 6-311ϩG** basis set.Experimental All chemicals were available in commercial. Phenyl propane-1,2-dione, N-methyl ethylenediamine and phenyl isocyanate were purchased from Tokyo Chemical Industry Co., Ltd., ethylenediamine and acetonitrile were from Kanto Chemical Co., Inc. Deuterium oxide and pyridine-d 5 were also purchased from CEA, and DMSO-d 6 was from Isotec Inc. Melting points were measured wi...

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“…Substituted α-diketones are important building blocks for the synthesis of a variety of heterocyclic compounds, like 1,2,4triazines (Zhao et al 2003), chinoxalines (Zhao et al 2004), pyrimidines (Ohta et al 1982) or imidazoles .…”

Section: S1 Commentmentioning

confidence: 99%

1-[2-(Benzylamino)-4-pyridyl]-2-(4-fluorophenyl)ethane-1,2-dione

et al. 2009

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The crystal structure of the title compound, C20H15FN2O2, contains two crystallographically independent molecules, which are related by a pseudo-inversion center and linked into dimers via intermolecular N—H⋯N hydrogen bonds. The 4-fluorophenyl ring of molecule A makes dihedral angles of 17.17 (16) and 62.25 (15)°, respectively, with the phenyl and pyridine rings. The 4-fluorophenyl ring of molecule B makes dihedral angles of 8.50 (16) and 64.59 (15)°, respectively, with the phenyl and pyridine rings. The dihedral angle between the pyridine ring and the phenyl ring of molecule A [60.97 (15)°] is bigger than in molecule B [59.49 (15)°]. The dihedral angle between the two pyridine rings is 1.37 (14)° and between the two phenyl rings is 3.64 (16)°.

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Syntheses and reactions of some 2,3‐disubstituted pyrazine monoxides

Cited by 28 publications

References 13 publications

Monocationic Iridium(III) Complexes with Far‐Red Charge‐Transfer Absorption and Near‐IR Emission: Synthesis, Photophysics, and Reverse Saturable Absorption

Monocationic Iridium(III) Complexes with Far‐Red Charge‐Transfer Absorption and Near‐IR Emission: Synthesis, Photophysics, and Reverse Saturable Absorption

Latent Enamine Functionality of 5-Methyl-2,3-dihydropyrazines

1-[2-(Benzylamino)-4-pyridyl]-2-(4-fluorophenyl)ethane-1,2-dione

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