Synthesis Of 2,3-dichloropyridine

2,3-dichloropyridine is a very important chemical intermediate, widely used in pesticide and medicine, it is also an important raw material of synthetic Chlorantraniliprole. Chlorantraniliprole pesticides which owns unique mechanism of action, a broad spectrum insecticide, efficiency and low toxicity, high specificity, environmentally friendly is no cross-resistance with other insecticides, this type of insecticide has broad prospects for application and development. Therefore, As a important chemical raw materials of synthesis of chlorantraniliprole pesticides, synthesis of 2,3-dichloro-pyridine is a very important the theoretical basis and practical significance.This paper reviews in detail the various preparation of 2,3-dichloro-pyridine. And through the theoretical analysis and research, a synthetic route of 2,3-dichloro-pyridine industrialization was designed. 3-aminopyridine was synthesized from nicotinamide via Hofmann reaction with NaC lO solution and NaOH solution, 2-chloro-3-aminopyridine was synthesized from 3-aminopyridine chloridized with hydrogen peroxide/concentrated hydrochloric acid, finally, 2,3-dichloropyridine was prepared by diazotization and Sandmeyer reation with 2-chloro-3-aminopyridine at a low temperature and concentrated hydrochloric acid.The results show that the yield was 96.7% when reaction temperature was 85~90℃ and the material ratio was n( nicotinamide) : n( sodium hypochlorite) : n( NaOH) = 1:1.2:2.5 in the process of Hofmann reaction; The yield was 86.1% when reaction temperature was 15~20℃, the material ratio was n( 3-aminopyridine) : n(hydrogen peroxide) : n( HC l) = 1:1.25:11 in the process of Hydrogen peroxide/concentrated hydrochloric acid chlorination reaction. In the process of diazotization reaction with a low temperature and Sandmeyer reaction with 2-chloro-3-aminopyridine, the yield was 88.5% when the diazotization reaction temperature was 0~5℃, the material ratio was n(2-chloro-3-aminopyridine) : n(sodium nitrite) : n(HC l)=1:1:4, the amount of catalyst CuC l was 0.2 times of 3-aminopyridine, the Sandmeyer reaction temperature was 10~15℃. In this paper, through the experiments of the catalyst CuC l recycling experiments, we determine that the best times to apply the recovery is six times, greatly reducing the copper waste exclusion, reducing environmental pollution. In summary, the total yield for synthesis of 2,3-dichloro-pyridine is 73.7% calculating with nicotinamide. This route of synthesis which owns a simple process, simple and low prices of raw materials, simple and mild reaction conditions, simple post-processing has a good market prospect for industrial development.