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3-Chloro-2-fluoro-5-(trifluoromethyl)pyridine, a halogenated pyridine derivative, is a fluorinated building block. It participates in the synthesis of 2,3-difluoro-5-(trifluoromethyl)pyridine.

The general procedure for the synthesis of 3-chloro-2-fluoro-5-(trifluoromethyl)pyridine from 2,3-dichloro-5-trifluoromethylpyridine is as follows: Example 3b. Equipment: 250 mL four-necked round-bottomed flask equipped with a thermometer, mechanical stirrer, dropping funnel and inert gas inlet. Operating steps: 1. 25 mL of DMSO was added to a 250 mL four-necked round-bottomed flask, and the solvent was evaporated from a suspension of 150 mL of DMSO, 2.5 g of potassium carbonate (17.9 mmol), and 25.0 g of cesium fluoride (162.9 mmol) at 120 °C and 25-30 mbar pressure. 2. 25.0 g of 2,3-dichloro-5-trifluoromethylpyridine (112.3 mmol) was added to the reaction mixture and the reaction was stirred at 120 °C for 4 hours. 3. After completion of the reaction, the suspension was filtered and the product 3-chloro-2-fluoro-5-(trifluoromethyl)pyridine was distilled directly from the distillate at 95 to 115 °C and 40-60 mbar pressure to obtain the product in quantitative yield. PRODUCT ANALYSIS: GC analysis showed a product purity of 96.9 area percent.

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