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Process study for synthesizing 2,3,6-trichloropyridine from nicotinamide

A trichloropyridine and process research technology, which is applied in the field of nicotinamide synthesis of 2,3,6-trichloropyridine, can solve the problems of large amount of waste water, unavailable raw materials and high cost, so as to reduce the amount of waste water and promote two-phase Full response, cheap effect

Inactive Publication Date: 2018-09-04
ANHUI COSTAR BIOCHEM CO LTD
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Problems solved by technology

[0003] The advantage of the pyridine chlorination method is that the conversion rate is high and the three wastes in the process are less, but the product purification is difficult and the reaction yield is low
The advantages of 2,6-dichloropyridine liquid-phase or gas-phase chlorination method are less investment in fixed equipment and less industrial waste, but the disadvantage is that the product yield is not high; and one of the reaction raw materials is chlorine-smelling toxic chemicals, transportation and operation Both are inconvenient
Pentachloropyridine or tetrachloropyridine zinc powder reduction method uses zinc powder as a reducing agent to reduce pyridine. The operation is simple, but the raw material pyridine is toxic, and the large amount of zinc powder used in the production process leads to high production costs, and the process will generate a lot of waste water
[0004] All in all, the existing 2,3,6-trichloropyridine production process is difficult to operate, the cost is high, and the product yield is not ideal
In order to overcome the existing problems of 2,3,6-trichloropyridine, such as complex operation, low yield, unavailable and expensive raw materials, large amount of waste water, and potential safety hazards in the use of chlorine, the present invention proposes a synthesis method of niacinamide. The process of 2,3,6-trichloropyridine has simple, easy-to-obtain and cheap raw materials, simple and easy-to-operate reaction conditions, simple post-treatment, high yield, and has good industrial development prospects

Method used

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  • Process study for synthesizing 2,3,6-trichloropyridine from nicotinamide
  • Process study for synthesizing 2,3,6-trichloropyridine from nicotinamide
  • Process study for synthesizing 2,3,6-trichloropyridine from nicotinamide

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Embodiment 1

[0033] (1) Synthesis of 3-aminopyridine: At room temperature, add 500g of 10% sodium hydroxide solution to the reactor, lower the temperature below 10°C, add 61g of nicotinamide, stir to form a white turbid liquid, add dropwise 343g of 12.5 % sodium hypochlorite solution, control the dropping temperature to be less than 10°C, the reaction solution becomes clear and light yellow-green after dropping, rise to room temperature and stir for 0.5h, continue to heat up to about 90°C, keep warm for 2-3h, and detect nicotinamide by liquid chromatography The content is less than 0.1%. After the reaction is over, cool down to below 10°C, slowly add solid sodium hydroxide until the solution becomes white and turbid, then add ethyl acetate for extraction, and concentrate the organic phase to obtain 43.8g of light yellow solid 3-aminopyridine with a content of more than 95%, crude yield 93%.

[0034] (2) Synthesis of 6-dichloro-3-aminopyridine: add 37% hydrochloric acid 551.6g and Lewis aci...

Embodiment 2

[0037] (1) Synthesis of 2,6-dichloro-3-aminopyridine:

[0038]551.6 g of 37% hydrochloric acid was added into the reactor, and 43.8 g of self-made 3-aminopyridine was added slowly, the solution was raised to room temperature, and the solution turned pale yellow. Cool down to below 15°C, and start to add 74g of 30% hydrogen peroxide solution dropwise. After the dropwise addition, raise the temperature to 35-45°C, keep the temperature for 3-5 hours, and control the 3-aminopyridine in the liquid phase to less than 0.1%, and the reaction ends. Cool down to about 10°C, add saturated sodium metabisulfite solution to neutralize excess hydrogen peroxide until the starch potassium iodide test paper has no color change. Add 50% sodium hydroxide to adjust the pH to 3, add toluene to extract three times, combine the organic phases, then add 30% industrial hydrochloric acid to back-extract the by-product 2-chloro-3-aminopyridine in the organic phase, and concentrate the organic phase under...

Embodiment 3

[0040] (1) Synthesis of 2,3,6-trichloropyridine: Add 69.2g of homemade 2,6-dichloro-3-aminopyridine and 207g of 30% industrial hydrochloric acid, lower the temperature to below 0°C, and start to add 117.2g of 30 % sodium nitrite solution, after the dropwise addition, a diazonium salt solution was prepared, which was kept warm at about 0°C for later use. At room temperature, add 8.4g of cuprous chloride and 207g of 30% industrial hydrochloric acid to the reactor, and start to drop the diazonium salt solution at about 0°C under the protection of nitrogen, and gradually raise the temperature to 60-70°C after the addition, and react for about 2 hours. After the reaction was completed, dichloromethane was added to extract the reaction solution, and the organic phase was concentrated to obtain crude 2,3,6-trichloropyridine. Then add toluene and petroleum ether for recrystallization to obtain 58.1 g of white crystals with a content of 98% and a crude yield of 75%.

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Abstract

The invention provides a process study for synthesizing 2,3,6-trichloropyridine from nicotinamide. The process study comprises the following steps: with nicotinamide as a raw material, adding a sodiumhypochlorite solution in an alkaline environment to carry out a Hofmann downgrading reaction to obtain 3-aminopyridine; under catalysis of a Lewis acid catalyst, performing chlorination reaction under a concentrated hydrochloric acid / hydrogen peroxide condition to obtain 2,6-dichloro-3-aminopyridine; and reacting in the presence of sodium nitrite under low temperature and strong acid conditions to form a diazonium salt solution; and finally, performing a Sandmeyer reaction to obtain the target product, 2,3,6-trichloropyridine. The process material provided by the invention is simple, easily available and cheap, the reaction condition is simple and easy to operate, the post-treatment is simple, the yield is high, and thus the process has good industrial development prospects.

Description

technical field [0001] The invention relates to the field of organic synthesis, in particular to a process research on synthesizing 2,3,6-trichloropyridine from nicotinamide. Background technique [0002] Pyridine series, as important heterocyclic "three-drug and three-drug intermediate", have good biological activity, and the demand in people's life and production is increasing day by day. In particular, chloropyridine, as a novel three-drug intermediate with good biological activity, high product added value, green environmental protection, and no pollution to the environment, has become the most demanded three-drug intermediate in the world. Among them, 2,3,6-trichloropyridine is an important intermediate in the synthesis of herbicides, insecticides, and plant regulators. At present, the synthesis methods of 2,3,6-trichloropyridine mainly include pyridine chlorination method, 2,6-dichloropyridine liquid phase or gas phase chlorination method, pentachloropyridine or tetra...

Claims

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Application Information

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IPC IPC(8): C07D213/61
CPCC07D213/61
Inventor 刘善和温兰兰傅胜辉张令伟蒋伟
Owner ANHUI COSTAR BIOCHEM CO LTD
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