Study On The Synthesis Of Organic Intermediates Via Aromatic Amino Conversion

Aromatic amino compounds are important intermediates in pharmaceuticals, dye and agrochemicals. In this paper, the synthetic methods of some important organic compounds, such as 2-chloro-5-nitropyridine, 3-trifluoromethylphenol, 2-fluoro-5-nitropyridine were studied. The main results are as follows:The synthetic route of 2-chloro-5-nitropyridine was studied. It was prepared from 2-amino-5-nitropyridine by a three-step way including diazotization, hydrolysis and chlorination. This study focused on the effects of diazotization and hydrolysis process conditions such as the amount of sodium nitrite, the rate of dropping nitrite and time of reaction on the yield of 2-hydroxyl-5-nitropyridine. The effects on the chlorination yield of 2-hydroxyl-5-nitropyridine to 2-chloro-5-nitropyridine were caused by the amount of phosphorus oxychloride, phosphorus pentachloride and time of reaction. The purified conditions of 2-hydroxyl-5-nitropyridine and 2-chloro-5-nitropyridine were also proposed. The best yield of 2-chloro-5-nitropyridine is 66.5% (based on 2-amino-5-nitropyridine) with a purity of 99.9%.3-Trifluoromethylphenol was prepared by diazotization and hydrolysis reactions from 3-(trifluoromethyl)aniline. This study investigated the effects of various parameters, such as concentration of H2SO4, hydrolysis methods, and temperature of hydrolysis. The optimized conditions of 3-trifluoromethylphenol were as follows: n(3-(trifluoromethyl)aniline) : n(NaNO2) : n(H2SO4) = 1 : 1.5 : 4, adding urea to decomposition HNO2 with the method of hydrolysis while steam distillation. Also, 3g urea were added to hydrolysis solution in order to avoid the product being oxidized. The yield (purity) of 3-trifluoromethylphenol was 91.6% (99.7%).2-Fluoro-5-nitropyridine was synthesized by several ways, but it was difficult to separate the product due to many by-products. The mainly factors were studied in the 2-fluoro-5-nitropyridine synthesis reaction,...