Selective synthesis of oxazoles and pyrazines from <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:mrow><mml:mi mathvariant="bold">α</mml:mi></mml:mrow></mml:math>-bromo-1-phenylethanone using a by-product-promoted strategy

Liu, Changhui; Zhao, Jiateng; Qiao, Yu; Huang, Wenbo; Rao, Zhonghao; Gu, Yanlong

doi:10.1016/j.tet.2018.10.071

Cited by 7 publications

(6 citation statements)

References 42 publications

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“…Ligand screening showed that 2,2′-bipyridyl (bpy, L1) gave the highest yield. Moreover, replacement of palladium(II) acetate with other palladium catalysts, including Pd(PPh 3 ) 4 and Pd(PPh 3 ) 2 Cl 2 , resulted in lower yields (entry 2 vs entries [12][13][14].…”

Section: Paper Synthesismentioning

confidence: 99%

“…Classical methods for the synthesis of pyrazines include the condensation of -bromo ketones with NH 4 OAc (Scheme 1A). 14 However, this approach is limited to the construction of symmetrical 2,6-disubstituted pyrazines. Likewise, dehydrogenative dimerization of 1,2diols with NH 3 in the presence of Ru catalyst 15 gives rise to symmetrical 2,6-disubstituted pyrazines, albeit accompa-nied by a mixture of unsymmetrical 2,5-disubstituted pyrazines (Scheme 1A).…”

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confidence: 99%

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Palladium(II)-Catalyzed Intramolecular Tandem Cyclization Reaction for the Assembly of Unsymmetrical 2,6-Disubstituted Pyrazines

Chen¹,

Zhu²,

Wang³

et al. 2023

Synthesis

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Section: Paper Synthesismentioning

confidence: 99%

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confidence: 99%

Palladium(II)-Catalyzed Intramolecular Tandem Cyclization Reaction for the Assembly of Unsymmetrical 2,6-Disubstituted Pyrazines

Chen¹,

Zhu²,

Wang³

et al. 2023

Synthesis

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“…Additional references cited within the Supporting Information. [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]…”

Section: Procedures For the Suzuki-miyaura Coupling Reaction Using Lpdbrmentioning

confidence: 99%

Abnormal NHC Palladium(II) Complex Containing CNN Pincer Skeleton and Its Application to Suzuki‐Miyaura Coupling of Aryl Chlorides in Water

et al. 2023

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The excellent catalytic activities of abnormal NHC carbene complexes, where the C2 position remains unaffected, and coordination occurs at the C4 or C5 position of the imidazolium ring, is still a fascinating but scarce area of research. This present work reports a palladium complex (LPdBr) bearing abnormal NHC with CNN pincer architecture. It is synthesized from imidazolium‐based quinoline ligand (LH) with Pd(OAc)2 via ‐NH and carbene deprotonation. The complex was fully characterized by NMR spectroscopy (1D and 2D) and high‐resolution mass spectrometry (HRMS). The structure and abnormal coordination modes of the complex are further confirmed with the help of single‐crystal X‐ray diffraction. The studies revealed the abnormal coordination mode in LPdBr where C5 carbon of the imidazolium ring participates in bonding, leaving the C2 position unaffected. The catalytic potential of complex LPdBr was investigated in the Pd‐catalyzed Suzuki‐Miyaura coupling of various aryl/heteroaryl chlorides with different aryl/naphthyl/phenanthryl boronic acids. The catalyst LPdBr successfully activated various less‐activated aryl chloride substrates. LPdBr also exhibited good catalytic activity at 1 mol% Pd loading under microwave irradiation and in green solvent water. The mechanism of the catalytic cycle is investigated and proposed by HRMS.

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“…29−31 Among the heterocyclic compounds, the pyrazinyl group has attracted the attention of researchers because it is widely found in natural products or drugs. 32,33 Isolated pyrazine has a lower HOMO−LUMO energy gap compared to benzene. 34 And lone pair n electrons on pyrazine nitrogen atoms can form n−n and n−π interactions between the molecules of pyrazinyl compounds, 35 which can further reduce the energy gaps of the aggregates.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Heterocycles with lone pair n electrons can form intermolecular n – n , n –π interactions and decrease π–π interactions . The strong intermolecular interactions extend TSC, which is believed to be the mechanism of heterocyclic materials with efficient fluorescence emissions. − Among the heterocyclic compounds, the pyrazinyl group has attracted the attention of researchers because it is widely found in natural products or drugs. , Isolated pyrazine has a lower HOMO–LUMO energy gap compared to benzene . And lone pair n electrons on pyrazine nitrogen atoms can form n – n and n –π interactions between the molecules of pyrazinyl compounds, which can further reduce the energy gaps of the aggregates.…”

Section: Introductionmentioning

confidence: 99%

Pyrazine as a More Efficient Luminophore than Benzene for Producing Red-Shifted and Enhanced Photoluminescence

Bai,

Deng,

Xie

et al. 2023

J. Phys. Chem. A

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The development of organic photoluminescent (PL) materials with red-shifted and enhanced emissions is beneficial to promoting their applications. Luminescent materials based on aromatic heterocycles (e.g., pyrazine) usually have red-shifted and enhanced photoluminescence compared with phenyl-based luminescent materials. In this work, the photoluminescence behaviors of pyrazine and its derivatives (o-dichloro-, o-dicyano-, and dichlorodicyano-substituted) are compared with those of benzene and its derivatives. All compounds exhibit fluorescence emissions ranging from blue to yellow, and the fluorescence emissions of pyrazinyl compounds are more red-shifted than those of phenyl compounds. Except for the o-dicyano-substituted compound, pyrazinyl compounds exhibit stronger fluorescence emissions than corresponding phenyl compounds in both pure substances and ethanol solutions. In addition, both 5,6-dichloro-2,3-dicyanopyrazine (P4) and 4,5-dichloro-1,2-dicyanobenzene (B4) exhibit room temperature phosphorescence, and the maximum delayed emission wavelength is red-shifted from 575 nm of B4 to 637 nm of P4. The energy gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital of the monomers of pyrazinyl compounds are reduced by 0.07–1.37 eV compared with the monomers of phenyl compounds, which is the fundamental reason for the red-shifted emissions of the pyrazinyl compounds. Moreover, compared to B4, the smaller molecular spacing in the P4 crystal structure facilitates interlayer electron transfer and hence the formation of more extended through-space conjugation, resulting in the red-shifted emission of P4. This work proves that pyrazine is a more efficient luminophore than benzene for constructing PL compounds with longer emission wavelengths and higher quantum yields, which are important in guiding the design and preparation of organic PL materials.

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Selective synthesis of oxazoles and pyrazines from α-bromo-1-phenylethanone using a by-product-promoted strategy

Cited by 7 publications

References 42 publications

Palladium(II)-Catalyzed Intramolecular Tandem Cyclization Reaction for the Assembly of Unsymmetrical 2,6-Disubstituted Pyrazines

Palladium(II)-Catalyzed Intramolecular Tandem Cyclization Reaction for the Assembly of Unsymmetrical 2,6-Disubstituted Pyrazines

Abnormal NHC Palladium(II) Complex Containing CNN Pincer Skeleton and Its Application to Suzuki‐Miyaura Coupling of Aryl Chlorides in Water

Pyrazine as a More Efficient Luminophore than Benzene for Producing Red-Shifted and Enhanced Photoluminescence

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