Novel method for synthesizing 2,5-dichloro-3-fluoropyridine
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A technology of fluoropyridine and a new method, which is applied in the field of synthesis 2, can solve the problems of low yield and high cost of the target product, and achieve the effects of easy control, mild reaction process and simple reaction steps
Inactive Publication Date: 2012-07-04
NANJING REDSUN BIOCHEM CO LTD
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Patent US482288 reports that the yield of 2,3-difluoro-5-chloropyridine can reach between 20% and 50% by using a mixed fluorinating agent of potassium fluoride and cesium f...
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Embodiment 1
[0020] Add 100ml of water, 12.4g of sodium hypochlorite, 25g of sodium hydroxide into the four-necked reaction flask, cool down to -5°C, add 20g of 2,5-dichloronicotinamide, keep it warm for 2 hours, and then raise the temperature to 65°C and stir for 5 hours. Hours, cooling down after the reaction, the precipitated solid was 2,5-dichloro-3-aminopyridine, quantitative analysis showed 14g of 2,5-dichloro-3-aminopyridine with a purity of 92.7%. Add 14 g of the obtained 2,5-dichloro-3-aminopyridine to 74.5 g of 40 wt% fluoboric acid, cool to -5°C, add dropwise 35 ml of water containing 7.1 g of sodium nitrite, and keep -5 ℃ for 4 hours, after the reaction was completed, the temperature was raised to 25 ℃ and stirred for 10 hours. After the reaction, a white solid was obtained, which was the fluoroborate of 2,5-dichloro-3-fluoropyridine, and the obtained solid was filtered Heating to 60-70°C in petroleum ether, the white solid salt decomposes to obtain the target product 2,5-dichl...
Embodiment 2
[0022] The sodium hydroxide used in the reaction process is changed into potassium hydroxide, and the molar weight is consistent, all the other reaction conditions are identical with embodiment 1, finally obtain target product 2,5-dichloro-3-fluoropyridine, content is 93.8%, with 2 , 5-dichloronicotinamide calculation, its yield is 67.2%
Embodiment 3
[0024] During the reaction, except that the sodium hydroxide added was 18g, the rest of the reaction conditions were the same as in Example 1, and finally 2,5-dichloro-3-fluoropyridine with a content of 92% was obtained, calculated as 2,5-dichloronicotinamide , whose yield is 65.3%
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Abstract
The invention belongs to the field of chemical industry and discloses a novel method for synthesizing 2,5-dichloro-3-fluoropyridine. The method comprises the following steps of: performing Hofmann degradation on 2,5-dichloro-nicotinamide under the action of sodium hypobromite or sodium hypochlorite to obtain 2,5-dichloro-3-aminopyridine, and performing diazotization reaction on the 2,5-dichloro-3-aminopyridine, fluoboric acid and sodium nitrite to obtain the 2,5-dichloro-3-fluoropyridine. By the method, the yield of the 2,5-dichloro-3-fluoropyridine is greatly improved, and the total yield of the 2,5-dichloro-3-fluoropyridine can reach over 67 percent at most; and expensive 2,3,5-trichloropyridine is not used, and an expensive fluridizer is not used, so that the synthetic cost of the 2,5-dichloro-3-fluoropyridine is greatly reduced. Moreover, reaction steps are simple, the reaction process is mild, and the method is easy to control.
Description
technical field [0001] The invention belongs to the field of chemical industry and relates to a new method for synthesizing 2,5-dichloro-3-fluoropyridine. Background technique [0002] 2,5-dichloro-3-fluoropyridine is an important pesticide and pharmaceutical intermediate, and its market prospect is very promising. It is the key intermediate for the synthesis of pesticide clodinafop-propargyl. At present, the 2,3,5-trichloropyridine used in general reports is used as the starting material to synthesize 2,3-difluoro-5-chloropyridine, and the patent EP0097460 reports the use of 2,3,5-trichloropyridine in cesium fluoride as a catalyst , N, N-dimethyl sulfoxide as a solvent, the yield of 29% of 2,3-difluoro-5-chloropyridine can be obtained. Patent US482288 reports that the yield of 2,3-difluoro-5-chloropyridine can reach between 20% and 50% by using a mixed fluorinating agent of potassium fluoride and cesium fluoride. Generally speaking, this type of method is due to The limit...
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