Background and overview[1]
3,5-Dichlorobenzoyl chloride is an important pesticide, pharmaceutical, and dye intermediate. In pesticide production, pesticides can be prepared through benzoic acidification reactions; in the pharmaceutical field, drugs for treating headaches and drugs for balancing antidiuretic hormone can be produced. In recent years, it has also been used to prepare purine derivatives, which are widely used in the medical field, especially the derivatives generated by reaction with amino acids have greater application and development prospects.
Preparation[2]
1) Synthesis of 3-bis(trichloromethyl)benzene (2) (side chain chlorination)
Add 160g (1.51mol) m-xylene, 0.16g (0.00066mol) benzoyl peroxide and 472.6g (1.51mol) 1,3-bis(trichloromethyl)benzene into a 500mL four-neck bottle. Raise the temperature to 60°C under light conditions and introduce chlorine gas. Adjust the chlorine gas flow until no chlorine gas escapes in the tail gas. Control the temperature at 110°C and terminate the gas phase monitoring reaction. The crude product is distilled under reduced pressure at about 1.33kPa, and the fraction between 160 and 162°C is the product, with a purity of 99.4% and a yield of 92.5%.
2) Synthesis of 5-chloro-1,3-bis(trichloromethyl)benzene (3) (chlorination of benzene ring)
Add 156.5g (0.50mol) compound 2 and 1.57g (0.0097mol) anhydrous ferric chloride catalyst into a 500mL four-neck bottle, heat to 60°C with stirring, start to pass chlorine gas, and adjust the chlorine gas flow to the tail gas No chlorine gas escapes. The temperature is controlled at 100°C. The gas phase monitoring reaction is terminated. The reaction liquid is distilled under reduced pressure at about 1.33kPa. The fraction between 171 and 173°C is the product with a purity of 96.0% and a yield of 82.4%.
3) Synthesis (hydrolysis) of 5-chloroisophthaloyl chloride (4)
Add 350g (1.007mol) compound 3 and 3.5g (0.0216mol) ferric chloride catalyst into a 500mL four-neck bottle, heat to 80°C with stirring, slowly add 36g (2mol) water dropwise within 3.5h, and After the temperature was raised to 130°C, the gas phase monitoring reaction stopped and 232.6g of crude product was obtained. The temperature drops to about 50°C, and the crude product is distilled under reduced pressure at 1.73kPa. The fraction between 149 and 151°C is the product, with a purity of 98.3% and a yield of 94.5%.
4) Synthesis of 3,5-dichlorobenzoyl chloride (1) (decarbonylation reaction)
Add 97.9g (0.415mol) compound 4 and 0.98gPd/Al2O3 catalyst into a 100mL four-neck bottle, and raise the temperature to 290°C with stirring. When by-products begin to appear during chromatographic monitoring, continue the reaction after evaporating the product, and repeat the reaction and distillation process until there is no raw material in the reaction. The distilled fraction was rectified at 1.73kPa, and the fraction between 125 and 127°C was the product, with a purity of 99.2% and a yield of 87.5%. 1HNMR (CDCl3, 400MHz), δ: 7.976 (d, 1H, J=2.0Hz, ArH); 7.976 (d, 1H, J=2.0Hz, ArH); 7.655 (d, 1H, J=2.0Hz, ArH).
References
[1] Wang Qian, Sun Haichao, Liu Xiaoxiang. Research on the synthesis process of 3,5-dichlorobenzoyl chloride [J]. Chemistry and Adhesion, 2018, 40(02): 118-120.
[2]Niu Binbo, Liu Yan, Liu Wei, Geng Li, Du Xiaoyu, Chen Fang. Research on the synthesis of 3,5-dichlorobenzoyl chloride[J]. Chemical Reagents, 2015, 37(02): 176-178.
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