Preparation background and overview of 3-(trifluoromethyl)pyridine-2-thiol
3-(Trifluoromethyl)pyridine-2-thiol, also known as 2-mercapto-3-trifluoromethylpyridine, is an important intermediate with wide applications in the fields of organic synthesis, medicine, pesticides, etc. the use of. 2-Mercapto-3-trifluoromethylpyridine is the key intermediate of the herbicide abisulfuron-methyl, which is a new sulfonylurea herbicide developed by Ishihara Sangyo Co., Ltd. of Japan. It is mainly used to control and control warm seasons. It also has good control effect on annual or perennial broadleaf weeds and sedge weeds in lawns, and has the characteristics of low toxicity and high efficiency.
Preparation of 3-(trifluoromethyl)pyridine-2-thiol
Preparation report of 3-(trifluoromethyl)pyridine-2-thiol 1.
Chloropyridine
1) First add 60% NaHS to dimethylformamide (DMF) to obtain a blue solution, then add NaOH and sulfur in sequence to obtain a brown solution, and heat the brown solution from room temperature to 60°C~ 70℃, and react at a temperature of 60℃~70℃ for 50min~70min. After the reaction is completed, add 2-chloro-3-trifluoromethylpyridine, and then increase the temperature from 60℃~70℃ to 110℃~130℃ , and react lepidolite at a temperature of 110°C to 130°C for 1.5h to 2.5h to obtain crude 2-mercapto-3-trifluoromethylpyridine (dark brown solution); the 60% NaHS and dimethyl The mass ratio of formamide is (0.1~0.3):1; the mass ratio of NaOH and dimethylformamide is (0.1~0.3):1; the mass ratio of sulfur and dimethylformamide is (0.1~0.3): 1; the mass ratio of the 2-chloro-3-trifluoromethylpyridine and dimethylformamide is (0.1~0.3): 1;
2) Post-treatment: Pour the crude 2-mercapto-3-trifluoromethylpyridine obtained in step 1) into ice water, then use hydrochloric acid to adjust the pH to 1.9~2.1, and then raise the temperature to 85℃~95℃ , and stir for 8min~12min at a temperature of 85°C~95°C, then perform suction filtration, and rinse twice with deionized water at a temperature of 80°C. Cool the filtrate obtained by suction filtration to -5°C~0°C, and repeat Carry out suction filtration, and dry the solid obtained after suction filtration to a constant weight to obtain 2-mercapto-3-trifluoromethylpyridine; the volume of the ice water and crude 2-mercapto-3-trifluoromethylpyridine The ratio is (5~7):1.
Preparation report of 3-(trifluoromethyl)pyridine-2-thiol 2.
Add 4.5g (0.025mol) 2-chloro-3-trifluoromethylpyridine, 2.75g (0.025mol) sodium polysulfide, 20ml free Water ethanol, heat and reflux for about 6 hours. After the reaction is completed, distill under normal pressure to recover the ethanol. Add hydrochloric acid dropwise to the reaction bottle while stirring to adjust the pH value of the solution to 2. Filter to obtain yellow 2-mercapto-3. – Crude trifluoromethylpyridine. Dissolve the above crude 2-mercapto-3-trifluoromethylpyridine in an alkali solution with a pH of 9 to 10, and stir for 2 hours. Filter, wash the filter cake twice with 10 ml of water, adjust the pH value of the filtrate to 2 with hydrochloric acid, and precipitate a large amount of light yellow solid, filter and dry to obtain 1.9g of 2-mercapto-3-trifluoromethylpyridine product, melting point 175-177 ℃, content 99.9% (HPLC), yield 43.3%.
References
[1]CN201310294235.1 Triazolopyrimidine sulfonamide compounds and synthesis methods and applications
[2]CN200810019607.9 A kind of preparation method of 2-mercapto-3-trifluoromethylpyridine
