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Method for preparing 2,3-dichloropyridine

A technology of dichloropyridine and aminopyridine, which is applied in the field of organic synthesis in the chemical industry, can solve the problems of increasing operating procedures and labor intensity, difficulty in evaporating solvents, and increasing production costs, so as to save preparation work and have a good appearance , the effect of increasing productivity

Active Publication Date: 2008-11-12
CANGZHOU LINGANG YANUO CHEM CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In CN1807414, cuprous chloride is used as the catalyzer of diazonium salt decomposition, and cuprous chloride is generally all used and made now, so a lot of repetitive work will be done, which increases the operational strength of the operating procedures and workmen, and increases the Investment in equipment leads to an increase in production costs
When extracting 2,3-dichloropyridine products, the above two patents all chose the method of using organic solvent extraction and then evaporating the solvent under reduced pressure. Dry solvents are more difficult to achieve
From the perspective of the physical properties of 2,3-dichloropyridine itself, it is unrealistic to use evaporation to dryness, because 2,3-dichloropyridine is very easy to sublimate, and it can sublimate quickly at 40°C, so it is difficult to concentrate During the process, as the solvent evaporates, 2,3-dichloropyridine will be taken away, resulting in product loss, and may block the pipeline, causing accidents

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0021]Add 47g (0.5mol) 3-aminopyridine, 270g36% concentrated hydrochloric acid and 2g (0.016mol) chlorine For ferrous oxide, heat up to 55°C until all solids are dissolved, then cool down to 25°C. After bubbling 56.8g of chlorine into the reaction bottle at 25-30°C, sample HPLC to monitor 6.3% of 3-aminopyridine, 83.6% of 2-chloro-3-aminopyridine, 2,6-dichloro-3-amino Pyridine 10%, stop the chlorine gas. At this time, the reaction solution was dark red. HPLC analysis showed that the reaction solution contained approximately 52.1 g of 2-chloro-3-aminopyridine, that is, the molar yield of 2-chloro-3-aminopyridine in the chlorination reaction was 81.1% based on 3-aminopyridine. 190 g of 36% hydrochloric acid and 36 g (0.25 mol) of cuprous oxide were added to the reaction liquid, and the temperature was lowered to 25°C. Start to drop 209 g (1 mol) of 33% sodium nitrite aqueous solution, and the dropwise addition is completed in about 1.5 hours. At this time, the temperature of ...

Embodiment 2

[0023] Add 47g (0.5mol) 3-aminopyridine, 270g36% concentrated hydrochloric acid and 2g (0.016) ferrous chloride in the 1000ml four-neck flask with mechanical stirring, thermometer, constant pressure dropping funnel and reflux condenser, stir The temperature was raised to 55°C, the solid was dissolved, and then the temperature was lowered to 25°C. 94g of 27% hydrogen peroxide was added dropwise at 25-30°C, and the color of the reaction solution gradually deepened with the addition of hydrogen peroxide. After dripping hydrogen peroxide, react at 25-30°C for 20 minutes to take samples, and HPLC monitors 9% of 3-aminopyridine, 81.2% of 2-chloro-3-aminopyridine, and 10.8% of 2,6-dichloro-3-aminopyridine. When the reaction solution was dark red, HPLC analysis showed that the reaction solution contained about 50.6g of 2-chloro-3-aminopyridine, and the molar yield of 2-chloro-3-aminopyridine was 78.8% based on 3-aminopyridine. 190 g of 36% hydrochloric acid and 36 g (0.25 mol) of cup...

Embodiment 3～6

[0025] Except the catalyzer of the first step chlorination reaction, all the other steps are identical with embodiment 1, and experimental result is listed in the following table:

[0026] Example number

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Abstract

The invention discloses a method for preparing 2,3-dichloropyridine with a simple process and a high yield rate. The method is as follows: in a concentrated hydrochloric acid, 3-aminopyridine is used as a starting material, Fe<2> or Fe <3> is used as a chlorination catalyst, and a mixture of hydrogen peroxide and hydrochloric acid or chlorine is used as a chlorating agent to conduct a chlorination reaction to chloridize the 3-aminopyridine. The reaction mixtures without being separated are added with Cu<+> or Cu<2+> which serves as a catalyst for diazotization / chlorination reaction and with an aqueous solution sodium nitrite to conduct diazotization / chlorination reaction to prepare 2,3-dichloropyridine by a one-pot process. The 2,3-dichloropyridine is isolated and purified by a normal method with a purity more than 99.2 percent. According to a 3-aminopyridine based calculation, the molar yield rate of the 2,3-dichloropyridine is more than 74.1 percent.

Description

technical field [0001] The invention relates to a method for preparing 2,3-dichloropyridine, which belongs to the technical field of organic synthesis in the chemical industry. Background technique [0002] In the technical field of organic synthesis in the chemical industry, 2,3-dichloropyridine is an important intermediate in organic synthesis and is widely used in the fields of medicine and pesticides. At present, related methods for preparing 2,3-dichloropyridine include: the method introduced in JP1193246 (1989) is prepared by catalytic reduction reaction using 2,3,6-trichloropyridine as raw material. And introduce in CN1910152 (2005) take nicotinamide as starting material through Hoffman degradation, chlorination, diazotization, chlorination, obtain 2,3-dichloropyridine, do not use catalyzer in this method chlorination reaction, The diazotization reaction uses Cu 2+ Catalysts containing more than 50%. The 2,3-dichloropyridine product obtained by this method has a pa...

Claims

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Application Information

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IPC IPC(8): C07D213/61
Inventor 刘晓民
Owner CANGZHOU LINGANG YANUO CHEM CO LTD
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