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A synthetic method, the technology of chloropyridine, applied in 2 fields, can solve the problem of high price, achieve simple operation and solve the effect of low yield
Inactive Publication Date: 2010-02-17
NANJING REDSUN BIOCHEM CO LTD +1
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Problems solved by technology
[0006] All the above-mentioned halogen replacement reactions not only need to use cesium fluoride with higher price, but also the yield is only about 30% at most
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Embodiment 1
[0024] 2,3,5-Trichloropyridine (18.2g, 0.1mol), potassium fluoride (13.9g, 0.24mol, pre-vacuum-dried at 140°C for 12 hours) were dissolved in 50mL sulfolane, under nitrogen protection, heated to 120°C, Added 1.2 g of tetraphenylphosphine bromide, maintained at 180°C for 5 hours, and then maintained at 200°C for 12 hours. According to gas phase analysis, the yield of 2,3-difluoro-5-chloropyridine was 39.1%, and the conversion rate of 2,3,5-trichloropyridine was 99%.
Embodiment 2
[0026] 2,3,5-Trichloropyridine (18.2 g, 0.1 mol), potassium fluoride (17.4 g, 0.3 mol, pre-vacuum-dried at 140°C for 12 hours) were dissolved in 100 mL of N-methylpyrrolidone, protected by argon. Heated to 120°C, added 2.0 g of tetrabutylphosphine bromide, maintained at 185°C for 7 hours, and then maintained at 205°C for 15 hours. According to gas phase analysis, the yield of 2,3-difluoro-5-chloropyridine was 42%, and the conversion rate of 2,3,5-trichloropyridine was 100%.
Embodiment 3
[0028] 2,3,5-Trichloropyridine (18.2g, 0.1mol), potassium fluoride (23.1g, 0.4mol, pre-vacuum-dried at 140°C for 12 hours) were dissolved in 100mL N-methylpyrrolidone, protected by argon, Heated to 120°C, added 1.0g of tetrabutylphosphine bromide, maintained at 190°C for 10 hours, and then maintained at 205°C for 10 hours, the yield of 2,3-difluoro-5-chloropyridine was 40%, 2 , What is the conversion rate of 3,5-trichloropyridine 100%.
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Abstract
The invention discloses a synthesis method of 2,3-difluoro-5-chloropyridine, and the method comprises the following steps: in organic solvent, adopting 2,3,5-trichlopyridine and potassium fluoride asraw materials and tetraphenylphosphonium bromide or tetrabutylphosphonium bromide as phase transfer catalyst, keeping temperature at 180-190 DEG C for 5-10h under the protection of inert gas and keeping temperature at 200-210 DEG C for 10-15h to prepare 2,3-difluoro-5-chloropyridine. The synthesis method of 2,3-difluoro-5-chloropyridine of the invention adopts cheap and accessible potassium fluoride as fluorinating agent and adds phase transfer catalyst and controls the reaction temperature to prepare high yield 2,3-difluoro-5-chloropyridine, thus avoiding to use more expensive fluorinating agent such as caesium fluoride and the like and solving the defect that the yield of the reaction that potassium fluoride is directly used to perform fluorination is low. The method of the invention hassimple operation and is applicable to the large-scale production of 2,3-difluoro-5-chloropyridine.
Description
technical field [0001] The invention belongs to the field of chemical industry, and in particular relates to a synthesis method of 2,3-difluoro-5-chloropyridine. Background technique [0002] 2,3-Difluoro-5-chloropyridine is an important intermediate in the synthesis of high-efficiency pesticide clodinafop-propargyl. Due to the strong polarity of fluorine, it is difficult for fluorine molecules to be polarized. Therefore, it is very difficult to generate positive fluoride ions, so electrophilic substitution fluorination is not easy to occur. Moreover, fluorine molecules are relatively active, and are easily dissociated into free radicals. They react violently with organic hydrocarbons, release a lot of heat, and often have side reactions such as bond breaking or ring breaking. The reactions are very complicated and difficult to control. Therefore, there is an explosion hazard with direct fluorination. [0003] In order to prepare the required fluorides, the fluorine group ...
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