- Palladium catalyzed Carbon–Hydrogen bond activation on amino-substituted quinones under acidic condition
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In this study, 2-(benzylamino)naphthalene-1,4-dione (4a) was used as the starting material to carry out a one-pot catalytic reaction in acetic acid with divalent palladium metal Pd(OAc)2 in a nitrogen atmosphere. Two compounds, 5a and 6a, were observed unexpectedly. Both compounds were characterized by spectroscopic methods as well as X-ray single crystal determination. The crystal structure of 5a reveals that a nitrogen-containing six-membered ring is formed; while the crystal structure of 6a shows that both oxazole and pyridine ring are generated. The optimized condition for making 6a was pursued. Derivatives of 4a, such as 4b and 4c, were also used as starting materials to proceed under the aforementioned optimal reaction conditions. Although the yields are not satisfactory, obviously the same patterns of corresponding compounds can be synthesized. The reaction of a 4a-structural related compound 9 under similar condition, two unexpected oxazole-containing compounds, 10 and 11, were obtained. The diverse pathways for this type of reactions even starting with slightly different substituents on the quinone indeed provides chemists with a perpetual motivation for further studies.
- Huang, Peng-Hao,Hong, Rui-Yu,Hong, Fung-E
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p. 2337 - 2347
(2021/10/08)
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- Benzoxazole-Linked Ultrastable Covalent Organic Frameworks for Photocatalysis
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The structural uniqueness of covalent organic frameworks (COFs) has brought these new materials great potential for advanced applications. One of the key aspects yet to be developed is how to improve the robustness of covalently linked reticular frameworks. In order to make the best use of π-conjugated structures, we develop herein a ";killing two birds with one stone" strategy and construct a series of ultrastable benzoxazole-based COFs (denoted as LZU-190, LZU-191, and LZU-192) as metal-free photocatalysts. Benefiting from the formation of benzoxazole rings through reversible/irreversible cascade reactions, the synthesized COFs exhibit permanent stability in the presence of strong acid (9 M HCl), strong base (9 M NaOH), and sunlight. Meanwhile, reticulation of the benzoxazole moiety into the π-conjugated COF frameworks decreases the optical band gap and therefore increases the capability for visible-light absorption. As a result, the excellent photoactivity and unprecedented recyclability of LZU-190 (for at least 20 catalytic runs, each with a product yield of 99%) have been illustrated in the visible-light-driven oxidative hydroxylation of arylboronic acids to phenols. This contribution represents the first report on the photocatalytic application of benzoxazole-based structures, which not only sheds new light on the exploration of robust organophotocatalysts from small molecules to extended frameworks but also offers in-depth understanding of the structure-activity relationship toward practical applications of COF materials.
- Wei, Pi-Feng,Qi, Ming-Zhu,Wang, Zhi-Peng,Ding, San-Yuan,Yu, Wei,Liu, Qiang,Wang, Li-Ke,Wang, Huai-Zhen,An, Wan-Kai,Wang, Wei
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supporting information
p. 4623 - 4631
(2018/04/10)
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- Phenyliodine bis(trifluoroacetate) mediated intramolecular oxidative coupling of electron-rich N-phenyl benzamides
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The intramolecular oxidative C-O coupling of N-(4-alkoxy-phenyl) and N-(4-acetamido-phenyl) benzamides was achieved under metal-free conditions by using phenyliodine bis(trifluoroacetate) as oxidant and TMSOTf as catalyst. The reactions afford benzoxazole
- Yu, Zhengsen,Ma, Lijuan,Yu, Wei
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supporting information; experimental part
p. 1534 - 1540
(2012/07/27)
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