The main application background and overview of 3-methylpyridine oxide
3-METHYLPYRIDINE N-OXIDE (3-METHYLPYRIDINE N-OXIDE) is usually a white to light yellow crystal and is an intermediate in the synthesis of important drugs such as imidacloprid and ethosiprid. At present, 2-chloro-3-methylpyridine and 2-chloro-5-methylpyridine synthesized by the reaction of 3-methylpyridine-N-oxide and phosphorus oxychloride are widely used in pesticide and pharmaceutical synthesis. Has a wide range of applications.
3-Methylpyridine oxide is an organic compound that can be used to prepare 2-chloro-5-methylpyridine compounds. 2-Chloro-5-methylpyridine is an important intermediate in the production of pesticides imidacloprid and imidacloprid. Imidacloprid and di-tert-butylpyridinib are chlorinated nicotine insecticides, which have contact and stomach poisoning effects on pests, and have excellent systemic activity. They are highly efficient, broad-spectrum, safe and effective. An insecticide with a novel mechanism, it has special effects on pests that are severely resistant to organophosphorus, carbamate and synthetic pyrethroids.
Main applications of 3-methylpyridine oxide
A method for preparing 2-chloro-5-methylpyridine (I) compound, which is characterized by comprising the following steps:
(1) First add the compound of formula (II), 3-methylpyridine oxide, into the diluent. After cooling, first add the electrophile reagent slowly and dropwise, and then the organic nitrogen base. Stir when adding. The molar ratio of the diluent to the electrophile and the organic nitrogen base is 1:1-10:1-10. The reaction is carried out at -60-100°C to obtain the compound of formula (III). In formula (III), X represents deionization. Chlorine electrophile or decarboxylation corresponding group; (2) Use the compound of formula (III) and the chlorinating agent as reactants in a molar ratio of 1:0.1-20, with a diluent or an excess of other chlorinating agent As a solvent, react under normal pressure or high pressure at 40-200°C to obtain the formula 2-chloro-5-methylpyridine compound (I).
Example:
Add 80g, 0.7339mol 3-picoline oxide into 550g methylene chloride, cool the mixture to -10°C, slowly add 206g, 1.4679mol benzoyl chloride and 148.2g, 1.4679mol triethylamine dropwise , after the dropwise addition is completed, reflux and stir for 1 hour, suction filtration, the filtrate is distilled to remove methylene chloride, and 5-methylpyridine-2-benzoate is separated by distillation.
Add 600ml of chlorobenzene to the above mixture, add dropwise 42g and 0.2736mol of phosphorus oxychloride, and raise the temperature to reflux for 6 hours. After the reaction was completed, it was hydrolyzed, neutralized with liquid caustic soda, and steam distilled to obtain the compound of formula (I) with a yield of 82.2%.
Main application preparation of 3-methylpyridine oxide
Figure 1 is a process flow chart.
In the picture: 1–A storage tank; 2-B storage tank; 3-3-methylpyridine and catalyst transport pump; 4-hydrogen peroxide transport pump; 5-micromixer; 6-microreactor High-temperature reaction section; 7-microreactor low-temperature cooling section; 8-flash separator; 9-3-methylpyridine-N-oxide product; 10-catalyst reuse.
1) Weigh 240g of 3-methylpyridine and 2.4g of catalyst to prepare material liquid A, weigh 275g of 35wt% hydrogen peroxide solution, stabilize it with phosphate buffer to pH=4, and prepare material liquid B; where The catalyst is a mixture of phosphomolybdic acid and molybdenum trioxide at a mass ratio of 2:1.
2) Control the heating temperature of the high-temperature reaction section 6 of the microreactor to 75°C. Feed liquid A and liquid B obtained in step 1) into the micromixer 5 at a flow rate of 50mL/min and 2mL/min respectively. , where A is the continuous phase and B is the dispersed phase. The structure of the micromixer 5 can be found in patent CN200510012114.9. It contains 5 parallel channels and uses 10 micron stainless steel porous media as the dispersion medium. The residence time of mixed liquid C in the high-temperature reaction section 6 of the microreactor is 4 minutes. After about 2 hours to complete the mixing and reaction process, ultra-high performance liquid chromatography was used to calibrate the product solution in tank A 1, and the yield of 3-methylpyridine-N-oxide reached 82.4%.
