Background and overview of synthesis and purification methods of 2,6-dimethylpyridine
2,6-Dimethylpyridine is an important organic synthesis intermediate and is widely used in the synthesis of medicines, pesticides, spices, industrial products, etc. 2,6-Dimethylpyridine was originally extracted from coal tar. In the early 1940s, the world’s energy structure changed to “replacing coal with oil”, which limited the source of this compound, and due to the shortage of pesticides, medicines, materials and other industries The development of this compound has greatly increased the demand for this compound, which has promoted the development of chemical synthesis methods of 2,6-dimethylpyridine.
Synthesis and purification methods of 2,6-dimethylpyridine
Synthesis and purification method of 2,6-dimethylpyridine Step 1, Preparation of 2,6-dimethyl-4-chloropyridine
In a 150ml three-necked flask, add 24.6g of 2,6-dimethyl-4-hydroxypyridine (0.2mol of nitrite tetrafluoroborate) and 4.2g of phosphorus pentachloride (0.01mol) at room temperature within 30 minutes. Add 46.0g (0.3mol) of phosphorus oxychloride dropwise. After the dripping is completed, raise the temperature to 110~115°C and continue the reaction for 9~11h. Finally, the reactant turns brown. Distillation to recover phosphorus oxychloride. Cool to room temperature naturally, slowly pour the reactant into 300ml of ice-water mixture, adjust pH to 8 with 20% Na2CO3 solution, extract with 3×100ml chloroform, anhydrous Na2SO4 Dry, distill to recover chloroform, distill the residue under reduced pressure, collect the fraction at 92-93°C/20mmHg, and obtain 26.7g of light yellow liquid, with a yield of 94.3% and a purity of 98.8%.
Synthesis and purification method of 2,6-dimethylpyridine Step 2, Preparation of 2,6-dimethylpyridine
Add 14.2g (0.1mol) of 2,6-dimethyl-4-chloropyridine, 0.4g of 5% Pd/C catalyst, 150ml of absolute ethanol, and N2 pyridinethione into a 250ml stainless steel high-pressure reactor. Remove the air in the autoclave by sodium replacement method, and finally introduce hydrogen to pressurize it to 0.1MPa. Turn on the stirrer and raise the temperature to 35-40°C. Use HPLC to monitor the reaction. After 10 hours, the raw materials will be completely converted and unreacted gas will be released. Turn on the high pressure Lid the kettle and take out the reactants. After filtration, the catalyst was recovered and used, ethanol was recovered from the mother liquor, and the 142-141°C fraction was collected by atmospheric distillation of the residual liquid to obtain 10.3g of colorless liquid with a yield of 96.2% and a purity of 99.2%.
Synthesis and purification methods of 2,6-lutidine Purification methods
Add 300g 2,6-lutidine into the three-necked flask, turn on the stirring, heat the water bath to 85 degrees Celsius, add 10g of water dropwise, and add urea in batches after the dropwise addition. After 1 hour of reaction, The water bath temperature was lowered to 75 degrees Celsius, and the reaction was continued for 4 hours. Then take out the flask and continue stirring at room temperature until the temperature of the material reaches room temperature. The reaction is over.
After the reaction is completed, the complex is filtered, washed twice with 100 ml of toluene, and the washings are combined and placed separately. 178g of complex was obtained, a total of 280ml of filtrate and primary washing liquid, and 110ml of secondary washing liquid. Filtrate As can be seen from the above table, the 2,6-dimethylpyridine content in the filtrate has dropped significantly, and the recovery rate is very high. After decomposition of the complex, the 2,6-dimethylpyridine content is about 99%.
References
[1][China invention, China invention authorization] CN201110332064.82, preparation method of 6-dimethylpyridine
[2][China invention, China invention authorization] CN200510060547.12, Preparation method of 6-dimethylpyridine
