Studies On The Synthetic Process Of 2,3-dichloropyridine

2,3-Dichloropyridine is a key intermediate of a novel anthranilic diamides insecticide Chlorantraniliprole with ryanodine receptors targets, which is discovered and developed by Du Pont. Chlorantraniliprole have a novel mode of action with unique chemical structure and show excellent efficacy, abroad insecticidal spectrum against lepidopterous insectpests, excellent safety against mammalian, and nocross-resistance to existing insecticides. They will be very suitable for insecticide resistance management and IPM programs.Based on the related literatures, several synthesis routes of 2,3-dichloropyridine were evaluated in this paper, therefore an reasonable synthesis of 2,3-dichloropyridine was explored, including Hofmann degradation, chlorination, diazotization, sandmeyer reaction start with nicotinamide , yield and purity of the product was 62% and 99% respectively. A one pot economic and industrialzed process from 3-aminopyridine without purify the intermediate also was developed, yield and purity of the product was 66% and 98% respectively.In this paper, the optimum process of 2,3-dichloropyridine were obtained via large quantity of exploratory and parallel experiments: in the procedure of 3-aminopyridine, enlightened from other literature methods, several amidohydrolysis inhibitors and its concentration were fixed on, improve the selectivity and yield; In the post-processing of 3-aminopyridine , for it great solubility in water, a set of continuous circumfluence extraction device was designed, greatly reducing the use of the extractant and got a yield up to 90%; in the synthesis of 2-chloro-3-aminopyridine, by way of optimization of various reaction conditions to reduce the over-chlorinated by-products, the final yield and purity of the product was more than 82.6% and 99% respectively. Appropriate catalyst and reaction temperature had been investigated when the 2,3-dicloropyridine is synthesized. The addition of extraction agent to sandmeyer reaction system was desired since it can reduce the bubble of the water phase and vigorous bumping, inhibit the formation of bipyridine, improve the selectivity .the reaction could afford excellent yield (up to >85%). 2,3-dichloropyridine was Synthesized from 3-aminopyridine in one pot, the intermediate product was used without future purification, the three-step reaction only use hydrochloric acid as solvent with one pot and got a final yield of more than 66%.In addition, the mechanism of related reactions were studied, the by-products were separated and characterized. The target compounds and its important intermediates also comfirmed by NMR and MS.