Method for synthesizing 2,6-difluoropyridine

Abstract

The invention relates to a method for synthesizing 2,6-difluoropyridine. The method comprises the following steps that: (1) a high boiling solvent and 2,6-dichloropyridine are added into a reaction kettle, and then potassium fluoride is added into the reaction kettle, wherein the dosage ratio of the 2,6-dichloropyridine to the high boiling solvent is 1gram per 4 to 10mL, and the mole ratio of the 2,6-dichloropyridine to the potassium fluoride is 1:2.0-3.0eq; (2) a phase transfer catalyst is added into the system with stirring; (3) the temperature of the system rises to 180 to 230 DEG C for reaction, and the products of the reaction are transferred out of the reaction system through distillation during reaction to promote the completion of the reaction; and (4), the distillate is subjected to washing with water, drying and vacuum filtration, the filtrate is distillated and the product is obtained. The method is simple, feasible, little in pollution, low in cost and suitable for large-scale production and provides a new thought and means for preparing 2,6-difluoropyridine.

Description

(1) Technical field: [0001] The invention relates to a synthesis method of 2,6-difluoropyridine. (2) Background technology: [0002] 2,6-Difluoropyridine is widely used in the production of medicines, pesticides, rubber and dyes; it is an important intermediate of pesticide chemicals, used in the preparation of herbicides and insecticides, and has important medicinal value and development prospects. [0003] At this stage, the main methods for preparing 2,6-difluoropyridine are as follows: [0004] 1. Using 2-amino-6-fluoropyridine as the starting material, it reacts with fluoroboric acid at -8~-10℃ to produce 2,6-difluoropyridine with a yield of about 27%, which is relatively low. , The cost of raw materials is high; Journal of Fluorine Chemistry, 27, 3965~3968; 1962; [0005] 2. Using pyridine as the starting material, it reacts with aluminum trifluoride and copper fluoride under high temperature conditions (450~500℃) to produce 2,6-difluoropyridine. The yield of this method is...

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Problems solved by technology

[0005] 2. Using pyridine as the starting material, react with aluminum trifluoride and copper fluoride under high temperature conditions (450-500°C) to generate 2,6-difluoropyridine. The yield of this method is low, only about 11%. , high reaction temperature, harsh reaction conditions, basically no value for industrial application; Organic Process Research & Development, 12(2), 349~354; 2008;

[0006] 3. Using 2,6-dichloropyridine as the starting material, 1,3-dimethylimidazolidinone as the solvent, and tetraphenylphosphine bromide as the phase transfer catalyst, react with potassium fluoride at 290°C Generate 2,6-difluoropyridine, this method has high yield, but the reaction temperature is high, it is difficult to achieve in scale-up production, and the cost is high, so it is not suitable for scale-up production; Angewandte Chemie, International Edition, 45(17), 2720-2725 ;2006;

[0007] The above method is not suitable for large-scale production due to the problems of expensive raw materials, low yield, and harsh reaction conditions.

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