One-step reaction method for preparing 4-nitropyridine-nitrogen oxide and halogenated-4-nitropyridine-nitrogen oxide

Abstract

This invention relates to a preparation method for 4-nitropyridines-nitrogenoxides and halogenated-4-nitropyridines-nitrogenoxides by one step, merging the separated oxidation and nitration into a single step. In the oxidation reaction, acetic anhydride, concentrated sulfuric acid, maleic anhydride and sodium bisulphate are added as catalyser; in nitration reaction, sodium nitrate is added to accelerate reaction. This method shortens the reaction time, especially the oxidation time reduced by half. After nitration reaction, 30~50% sodium hydroxide, instead of solid sodium carbonate, is used to neutralize the resultant solution to directly get the nitration resultants. In this method, the yield is more than 10% higher than that of routine methods and the production cost is cut down meanwhile.

Description

technical field [0001] The invention belongs to the preparation method of heterocyclic compounds in organic chemistry, especially a one-step reaction preparation method of halogenated-4-nitropyridine-nitrogen oxide Background technique [0002] Halogenated-4-nitropyridine-nitrogen oxide is obtained by chemical reduction reaction to obtain halogenated-4-aminopyridine, an important intermediate for the synthesis of pesticides, medicines, and cosmetics. Halogenated-4-nitropyridine-nitrogen oxide is derived from Halopyridine, the initial chemical raw material, is prepared by chemical oxidation and then nitration. Due to the harsh conditions of the electrophilic substitution reaction of halopyridine, the direct electrophilic substitution reaction can only obtain the 3-position substitution of the pyridine ring. Product, that is, if the halogenated pyridine is nitrated, only the halogenated 3-nitropyridine can be obtained. In order to make the halogenated pyridine easy to undergo ...

AI Technical Summary

Problems solved by technology

The first step of halopyridine oxidation is usually to use 50% hydrogen peroxide to oxidize halopyridine in acetic acid solvent, the reaction temperature is 85°C, and the reaction time is more than 24 hours, and the halopyridine is oxidized to halopyridine-nitrogen oxide. Thin-plate chromatography detected that the reaction was complete, evaporated the solvent acetic acid and the reaction solution under reduced pressure, added chloroform and a small amount of potassium carbonate to reflux at 65°C, filtered, washed the solid with chloroform, combined the chloroform solution, dried with anhydrous magnesium sulfate, and distilled The solvent chloroform is recovered to obtain halopyridine-nitrogen oxides; the second step of nitration is to dissolve the halopyridine-nitrogen oxides in concentrated sulfuric acid at low temperature, and then drop fuming nitric acid and sulfuric acid mixed acid for nitration at 90°C for several hours, and the thin plate layer After the analysis and detection reaction is complete, pour it into the ice-water mixture after cooling down, and neutralize it with solid sodium carbonate to obtain a yellow solid. After the yellow solid is dried, it is extracted with chloroform. Substitute-4-nitropyridine-nitrogen oxides, the two-step reaction time is too long, the steps are too many, and a large amount of chloroform with certain toxicity is used as solvent, which is harmful to human body and increases the cost. With 2- Chloropyridine is an example, in the small test of 150mL flask, two-step productive rate can only reach below 52%