Preparation of 2,5-dibromo-3-methylpyridine_Industrial additives

Preparation background and overview of 2,5-dibromo-3-methylpyridine

Pyridine and its derivatives are widely distributed in nature. Many plant ingredients such as alkaloids contain pyridine ring compounds in their structures. They are the basis for the production of many important compounds, such as medicines, pesticides, dyes, surfactants, rubber additives, feed additives, food additives, adhesives, etc. Indispensable raw materials in production. 2,5-Dibromo-3-methylpyridine is an important intermediate cyanopyridine in organic synthesis. It is mainly used as pharmaceutical intermediates, organic synthesis, and organic solvents. It can also be used in dye production, pesticide production, and spices.

Preparation of 2,5-dibromo-3-methylpyridine

Add 2-amino-3-methylpyridine (10.8g, 0.1mol) and acetic anhydride (12.3g, 0.12mol) into a 250ml four-necked flask, heat the oil bath to reflux, and use thin layer chromatography to track The reaction is complete. When the reaction solution cools down to 20-25°C, slowly add liquid bromine (17.6g, 0.11mol) dropwise. After the addition is completed, react at 50°C for 3 hours. Then add water to the system until all solids are dissolved, then slowly add 40ml40 % sodium hydroxide solution, continue the reaction for 30 minutes after adding, filter, dry, and recrystallize to obtain 2-amino-3-methyl-5-bromopyridine, with a molar yield of 64%.

Add 50ml of 48% hydrobromic acid solution into a 250ml three-necked bottle equipped with a stirrer and thermometer, dissolve 6.9g (0.048mol) cuprous bromide in the hydrobromic acid solution, and keep the temperature in an ice-water bath at -5°C Slowly add 7.6g (0.04mol) 2-amino-3-phenylboronic acid methyl-5-bromopyridine, maintain the temperature for 15min, slowly add 4.8ml of saturated sodium nitrite solution dropwise, stir for 2h after the addition, and use 40% hydrogen Neutralize the sodium oxide solution to pH=7-8, and distill under reduced pressure to obtain the product with a yield of 64%.

References

[1] [Chinese invention] CN201711090036.3 A preparation method of 2,5-dibromo-3-methylpyridine