2,3-二氯吡啶的合成新工艺

New synthetical method of 2,3-dichloropyridine

为满足市场需求,对2 ,3-二氯吡啶的合成工艺进行了研究.以2-氯烟酸为起始原料,经酰胺化、霍夫曼（Hofm ann）酰胺降解、重氮化和Sandmeyer 4 步反应,得到2 ,3-二氯吡啶,对影响产率的因素（如PC13 用量、NaOH 浓度、反应温度、催化剂用量）进行了优化.结果表明：酰胺化中,n（2 -氯烟酸）：w（PCl3） = l ： 0.45 ;霍夫曼降解反应中,NaOH 质量分数为18% ,反应温度为75？80°C;Sandmeyer反应中,n （2-氯-3-氨基p比咬）：n （氧化铜）= 1 ： 0. 3.在此优化条件下,反应总收率为70. 33% （以2-氯烟酸计）,纯度达98. 5% ,通过1 H -N M R 进行了结构表征.此法产品纯度高,操作简便,原料易得.

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 PCl_3,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(PCl_3)=1∶0.45,in Hofmann degradation,the concentration of NaOH is 18%,the reaction temperture is at75~80 ℃,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 1 H-NMR,which shows that the synthetic process has the advantages of high purity,simple operation and easily obtained raw material.