Abstract
Azo compounds have caused great interest in organic synthesis. They are widely used as dyes and analytical reagents. 1 Optical-switching and image storage can be made using azobenzene liquid crystal films. 2,3 Recently, many noteworthy studies have shown that some azo compounds possess excellent optical memory and photoelectric properties. 4,5 The oxidation of ArNHNHAr to azo compounds is an important transformation in organic synthesis. We have been paying particular and continuous attention to this field. In the previous work, NBS/pyridine 6 and FeCl3·6H2O 7 and galvinoxyl 8 have been used as effective reagents to synthesise azo benzene. These existing methods have their merits, but they also have drawbacks such as tedious operation and using a large amount of volatile and poisonous solvent, which affects human health and the environment. To continue our research on the synthesis of azo compounds, we decided to develop a new reagent system for the dehydrogenation of ArNHNHAr. The combination of sodium nitrite and sodium hydrogen sulfate in the presence of wet SiO2 has been used as an effective oxidising agent for the dehydrogenation of 4-substituted- 1,2,4-triazole-3,5-diones successfully. 9
Published Version
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