Preparation background and overview of 3-bromo-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxylic acid
3-Bromo-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxylic acid can be used as an intermediate for chlorantraniliprole. The Chinese trade name of chlorantraniliprole is Kangkuan. , is a new type of highly efficient and low-toxic o-carboxamidobenzamide insecticide developed by DuPont in the United States. It also has good insecticidal activity at very low concentrations and has special effects on lepidopteran insects. The chemical name is 3-bromo-N-{4-chloro-2-methyl-6-[(methylamino)carbonyl]phenyl}-1-(3-chloro-2-pyridyl)-1H-pyridine-5 -Amide.
Preparation of 3-bromo-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxylic acid
A preparation method of 3-bromo-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxylic acid, including the following steps:
1) Preliminary preparation: Prepare the reaction vessel, first select 2,3-dichloropyridine as the starting material, mix it with hydrazine hydrate to prepare 3-chloro-2-hydrazinopyridine, and then add it to the reaction vessel Ethanol and hydrazine hydrate, the ratio of ethanol to hydrazine hydrate is 1:4, add the ethanol solution dropwise under reflux and mix it, then heat it, the heating temperature is 150°C to 160°C, and the reflux time is 60 minutes to 80 Minutes, the reflux reaction time is 24 hours to 26 hours and the ice bath is cooled. After cooling in the ice bath, a large amount of solids precipitate, and the filter cake is dried by suction filtration to obtain white needle-shaped crystals;
2) After the preparation in step 1), white needle-shaped crystals are obtained. Add absolute ethanol with a content of 50-60mL and 20g of metallic sodium in the reaction vessel. At this time, heat and reflux until the sodium block is completely dissolved and then cool. , stir after cooling to room temperature. At this time, the reaction solution turns into a yellow emulsion and is heated to reflux. The reflux reaction time is 60 minutes to 80 minutes. Cool the temperature to 65C. Use glacial acetic acid to H5 for ice bath cooling and crystallization. Filter with suction, and dry the filter cake to obtain an earthy yellow solid;
3) Obtain an earthy yellow solid after the preparation in step 2). Add dichloroethane and benzenesulfonyl chloride to the reaction vessel, cool to 0°C and then stir. The stirring time is 50 minutes to 60 minutes. Stir During the process, triethylamine is added dropwise and the reaction is carried out at 0°C. The reaction time is 2 hours to 4 hours and the temperature is restored. When the temperature reaches 10°C-15°C, the gaseous hydrogen bromide compound is slowly introduced. The time is 45 minutes to 60 minutes, and then saturated sodium bicarbonate solution is added dropwise and mixed and washed. After mixing and washing until no bubbles are generated, the organic phase is separated and dried with anhydrous sodium sulfate. The solvent is removed under reduced pressure to obtain a dark red oil;
4) After the preparation in step 3), dark red oil is obtained. Add hydrocarbon groups and carboxyl groups in the reaction vessel and mix and stir for 30 minutes. Then add acetonitrile and concentrated sulfuric acid and stir for a second time. 15 minutes to 20 minutes. After stirring, add potassium persulfate and reflux. The reflux reaction time is 2 hours. After reflux is completed, filter. The filtrate is concentrated under reduced pressure to about 40 mL. Cool to 0°C in an ice bath and then filter with suction. The cake is dried to obtain a yellow solid, and the preparation is completed;
5) After preparing the sodium percarbonate, use a testing instrument to detect it and conduct a sampling test. The sampling ratio is based on the preparation sample range ratio of 1 to 100. The preparation of formyl phenylboronic acid can only be completed after the test structure is qualified. process.
References
[1]CN201910838472.7 Preparation method of 3-bromo-1-(3-chloro-2-pyridyl)-1H-pyrazole-5-carboxylic acid
