Background and overview of the preparation method of 2,6-dimethyl-3,5-dibromopyridine
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. 2,6-Dimethyl-3,5-dibromopyridine is an important intermediate in organic synthesis. It is mainly used in pharmaceutical intermediates, organic synthesis, organic sodium perborate tetrahydrate solvent, and can also be used in dye production and pesticide production. and spices, etc. At present, the reported synthesis methods of 2,6-dimethyl-3,5-dibromopyridine have shortcomings such as low yield and long process route.
Preparation method of 2,6-dimethyl-3,5-dibromopyridine
The synthesis method of 2,6-dimethyl-3,5-dibromopyridine includes the following steps:
Hydroxymethylpyridine
(1) Using 2,6-dimethyl-3-aminopyridine as raw material, add 2,6-dimethyl-3-aminopyridine and acetic anhydride into a four-necked flask, raise the temperature to reflux, and thinly Layer chromatography tracks the reaction;
(2) When the temperature of the reaction solution in step (1) drops below 23°C, add liquid bromine dropwise. After the dripping is completed, react at 40-55°C for 2-3 hours, then add water to the system until all solids are present. After dissolving, add sodium hydroxide solution dropwise. If a large amount of precipitate is formed, continue the reaction for 20-40 minutes. Filter, dry, and recrystallize to obtain 2,6-dimethyl-3-amino-5-bromopyridine;
(3) Add 2,6-dimethyl-3-amino-5-bromopyridine into the hydrogen bromide solution, and in the presence of a catalytic amount of copper bromide, add saturated sodium nitrite solution dropwise, and control the temperature React for 2-3 hours at -3-4°C to obtain 2,6-dimethyl-methyl-3,5-dibromopyridine.
