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, in particular to a one-step reaction preparation method of 4-nitropyridine-nitrogen oxide and halogenated-4-nitropyridine-nitrogen oxide. Background technique [0002] 4-nitropyridine-nitrogen oxides and halogenated-4-nitropyridine-nitrogen oxides are chemically reduced to obtain important intermediates 4-aminopyridine and halogenated-4-aminopyridines for the synthesis of pesticides, medicines, and cosmetics. 4-nitropyridine-nitrogen oxides and halogenated-4-nitropyridine-nitrogen oxides are prepared from the starting chemical raw materials pyridine and halogenated pyridines through chemical oxidation and then nitration. The conditions of the electrophilic substitution reaction of pyridine are harsh, and the direct electrophilic substitution reaction generally can only obtain the 3-position substitution product of the pyridine ring, that is, if pyridine and ...

AI Technical Summary

Problems solved by technology

The first step of oxidation of pyridine and halogenated pyridine is usually to use 50% hydrogen peroxide to oxidize pyridine or halogenated pyridine in acetic acid solvent. Nitrogen oxides or halogenated pyridine-nitrogen oxides, the reaction is complete as detected by thin plate chromatography, after evaporating off the solvent acetic acid and the reaction solution, add chloroform and a small amount of potassium carbonate to reflux extraction at 65°C, filter, wash the solid with chloroform, and combine the chloroform solution , after drying with anhydrous magnesium sulfate, the solvent chloroform is recovered by distillation to obtain pyridine-nitrogen oxides or halogenated pyridine-nitrogen oxides; the second step of nitration is to add pyridine-nitrogen oxides or halogenated pyridine-nitrogen oxides at low temperature Dissolve in concentrated sulfuric acid, then drop into fuming nitric acid and sulfuric acid mixed acid and nitrate at 90°C for several hours. After the reaction is complete by thin plate chromatography, pour it into ice-water mixture after cooling down, and neutralize it with solid sodium carbonate to obtain a yellow solid, yellow The solid is extracted with chloroform after drying, the extract is dried with anhydrous sodium sulfate, and the solvent chloroform is recovered by distillation to obtain 4-nitropyridine-nitrogen oxides and halogenated-4-nitropyridine-nitrogen oxides. The two-step reaction time It is too long, there are too many steps, and a large amount of chloroform with certain toxicity is used as a solvent, which is harmful to the human body and increases the cost. Taking 2-chloropyridine as an example, in the small test of a 150mL flask, the two-step yield is only Can reach below 52%