Methyl 5-broMo-6-Methylpicolinate

67-56-1

137778-20-2

1215860-20-0

Example 10: General procedure for the synthesis of methyl 5-bromo-6-methylpyridinecarboxylate. In a reactor equipped with a glass liner, 5-bromo-6-methylpyridine-2-carboxylic acid (30 kg, 138.9 mol) and methanol (133 kg, 4156 mol) were added sequentially. Thionyl chloride (36.8 kg, 309.2 mol) was slowly added under stirring conditions while the reaction temperature was controlled between 20-30 °C. The reaction temperature was controlled to be between 20-30 °C. After the addition was completed, the reaction mixture was heated to 55-65 °C and maintained at this temperature for 2 h of reaction. The progress of the reaction was monitored by high performance liquid chromatography (HPLC) and the reaction was terminated when the remaining amount of feedstock was less than 2%. Subsequently, the solvent was removed by distillation under reduced pressure at a temperature below 40 °C. Methyl tert-butyl ether (MTBE, 280 kg) was added to the residue and stirring was continued for 30 min to dissolve the crude product. The MTBE solution was transferred to a dry receiving drum. Water (300 kg) was added to the original reactor and the MTBE solution containing the crude product was pumped back into the reactor while maintaining the temperature in the reactor at 0-5°C and stirring for 1 hour. After completing the phase separation, the aqueous layer was extracted with MTBE (60 kg). All organic phases were combined and concentrated again under reduced pressure at a temperature below 40 °C. Hexane (60 kg) was added to the concentrated residue and the mixture was stirred, followed by centrifugation to separate and dry the resulting solid. The final product, methyl 5-bromo-6-methylpyridinecarboxylate (22.36 kg, 97.2 mol), was obtained as a white powder with a purity greater than 98% and a molar yield of 70%.