General procedure for the synthesis of 3-chloro-2-methylpyridine from 3-amino-2-methylpyridine: 54 g of 3-amino-2-methylpyridine was slowly added to 130 g of concentrated hydrochloric acid (36-38% mass fraction). Subsequently, hydrogen chloride gas was passed to saturation and 222.45 g of phosphoryl chloride and 90 g of nitric acid at 70% mass concentration were added dropwise at 20-25°C. The reaction was carried out with continuous stirring and strict stirring. The reaction was carried out with continuous stirring and under strict temperature control. After completion of the reaction, 57.3 g of 3-chloro-2-methylpyridine was obtained in 89% yield and 99% purity after post-treatment.
