Review of Synthesis of 2,3-Dichloro-5-Trifluoromethyl ...

Introduction

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CAS -84-7 2,3-Dichloro-5-Trifluoromethyl Pyridine is a highly sought-after fluorine-containing pyridine organic intermediate. This compound plays a crucial role in generating a variety of effective insecticides, including diafenthiuron and fenflunom, as well as the efficient herbicide fenflufop, and the advanced fungicide fluazinam, making it a key intermediate in the development of new pesticide varieties.

Overview of Synthetic Routes

1) Utilizing 2,3-Dichloro-5-Trichloromethylpyridine as a Raw Material

To synthesize the compound, begin by adding 106.16 g (0.4 mol) of 2,3-dichloro-5-trichloromethylpyridine along with 180 g (9 mol) of anhydrous hydrogen fluoride into a polyethylene reactor. Maintain the temperature at -20 °C during the first three hours of the reaction. Gradually introduce mercuric oxide while ensuring that the reaction temperature does not exceed 35 °C. Stir the mixture for roughly 22 hours after the addition is complete, until the solution becomes gray-white. Afterward, filter the mixture, neutralize the filtrate with sodium bicarbonate, extract with dichloromethane, and dry using anhydrous sodium sulfate. Finally, remove the dichloromethane under reduced pressure to isolate the product 2,3-dichloro-5-trifluoromethylpyridine, achieving a conversion rate of 100% and selectivity of 98%.

2) Using 3-Methylpyridine as a Raw Material

For this method, take 50 g of 2,3-dichloro-5-trichloromethylpyridine, add the catalyst, and heat the mixture to 170 °C. Gradually introduce anhydrous hydrogen fluoride gas and let it react for 11 hours. Upon completion of the reaction, utilize 5% sodium bicarbonate solution to support purification. Separate the organic phase, wash it with water, and dry to yield a crude product with a content of 85% and an overall yield of 65%.

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3) Using 2-Chloro-5-Trifluoromethylpyridine as a Raw Material

Begin with 363 g of 2-chloro-5-trifluoromethylpyridine, to which you will add 325 g of ferric chloride. Introduce chlorine gas into the mixture, heating it to a temperature range of 150-170 °C for a reaction duration of 18 hours. Once complete, transfer the reaction mixture into 1.5 L of hot water. Separate and dry the resultant oil layer using anhydrous sodium sulfate, then rectify to obtain 163 g of the final product.

Source

Review of Synthesis of 2,3-Dichloro-5-trifluoromethyl Pyridine [YUAN Qi-liang, SHEN De-long, LU Xin-xin, Fu Qing]

Description

2,3-Dichloro-5-(trifluoromethyl)pyridine is noted as an important intermediate in the synthesis of herbicides. Reports indicate that the synthesis of 2,3-dichloro-5-(trifluoromethyl)pyridine has been successfully carried out, including methods such as palladium-catalyzed monoalkoxycarbonylation.

Application

D (OTTO) 2,3-Dichloro-5-(trifluoromethyl)pyridine, 97% Cas -84-7 is utilized in the pharmaceutical and biochemical industries.