New synthetical method of 2,3-dichloropyridine

Abstract

In order to meet the market demand, the synthetic process of 2,3-dichloropyridine is studied. 2,3-dichloropyridine is synthesized from 2-chloronicotinic acid via amidation, Hofmann degradation, diazotization and Sandmeyer reaction. The factors influencing the yield (for example the amount of PCl3, the concentration of NaOH, the reaction temperature and the amount of catalyst) are optimized. The results show that the optimum conditions are as following: In amidation reaction, n(2-chloronicotinic acid)∶n(PCl3)=1∶0.45, in Hofmann degradation, the concentration of NaOH is 18%, the reaction temperture is at 75~80 ℃, and in Sandmeyer reaction, n(2-chloro-3-amino pyridine)∶n(CuO)=1∶0.3. Under the optimized conditions, the yield of the products is 70.33%(counted based on 2-chloronicotinic acid), the purity is 98.5%. The structure is characterized by 1H-NMR, which shows that the synthetic process has the advantages of high purity, simple operation and easily obtained raw material.

Keywords

• pesticide engineering
• 2
• 3-dichloropyridine
• 2-chloronicotinic acid
• Hofmann degradation
• diazotization
• Sand- meyer reaction