3376-50-9Relevant articles and documents
Chalcogen-Bonded Cocrystals of Substituted Pyridine N-Oxides and Chalcogenodiazoles: An X-ray Diffraction and Solid-State NMR Investigation
Xu, Yijue,Kumar, Vijith,Bradshaw, Maressa J. Z.,Bryce, David L.
, p. 7910 - 7920 (2020)
We introduce methyl, methoxy, and phenyl substituents at the para-, meta-, and ortho- positions of pyridine N-oxide to investigate the effect of chemical substitution on the resulting nine chalcogen-bonded structures formed upon cocrystallization with 3,4-dicyano-1,2,5-selenodiazole and 3,4-dicyano-1,2,5-telluradiazole. Single-crystal X-ray diffraction studies reveal the presence of double chalcogen bonding interactions in the cocrystals and demonstrate the impact of the substitution on the geometric features of the chalcogen bonds. 77Se and 125Te solid-state NMR spectroscopy is employed to measure selenium and tellurium chemical shift tensors of the products, and various trends are described. The smallest component of the 77Se chemical shift tensor (δ33) provides the strongest correlation with the chalcogen bond distance. Solution NMR provides qualitative evidence for the persistence of the chalcogen bonds in solution. Finally, 1J(77Se,14N) coupling constants in 3,4-dicyano-1,2,5-selenodiazole and its chalcogen-bonded cocrystals are measured after accounting for residual dipolar coupling between 77Se and 14N; however, changes in 1J(77Se,14N) attributable to chalcogen bonding upon cocrystallization are comparable to the experimental uncertainties. This systematic study of chalcogen-bonded cocrystals demonstrates the potential utility of the substitution effect for applications of chalcogen bonds in crystal engineering and demonstrates the value of solid-state NMR in characterizing such systems.
A pyridine nitrogen oxide high-efficient, multi-phase catalytic preparation method
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Paragraph 0068; 0072; 0073; 0074; 0075; 0118; 0122-0124, (2017/08/25)
The invention discloses a high efficient heterogeneous catalytic preparation method of pyridine oxynitride. In the provided preparation method, mono-substituted or poly-substituted pyridines or pyridine derivatives are taken as the primary raw materials, titanium dioxide loaded on tungsten (WO3/TiO2) is taken as the catalyst, hydrogen peroxide is taken as the oxidizing agent, and reactions are carried out in a water solution at a room temperature so as to obtain the target product. Compared with the prior art, the preparation method has the following advantages: (1) the provided oxidation method, no acetic acid is used, and thus the requirements on equipment are greatly reduced; (2) a heterogeneous catalytic method is adopted to prepare pyridine oxynitride, the catalyst can be separated from the reaction system through simple filtration or centrifugation, and the operation is convenient; (3) titanium dioxide loaded on tungsten is taken as the catalyst, pyridine oxynitride is prepared by one step in a water solution at a room temperature, the reaction conditions are mild, and the pollution to the environment is little.
Metal-free methylation of a pyridine N-oxide C-H bond by using peroxides
Li, Gang,Yang, Suling,Lv, Bingjie,Han, Qingqing,Ma, Xingxing,Sun, Kai,Wang, Zhiyong,Zhao, Feng,Lv, Yunhe,Wu, Hankui
supporting information, p. 11184 - 11188 (2015/11/27)
Metal-free methylation of a pyridine N-oxide C-H bond was developed using peroxide as a methyl reagent under neat conditions. Pyridine N-oxide derivatives with various groups (e.g., Cl, NO2, and OCH3) were all suitable substrates, and the desired products were obtained in moderate to excellent yields under standard conditions. Moreover, the methylation can be performed with a good yield on the gram-scale experiment. Tentative mechanistic studies show that the methylation is a classical radical process.
