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Vacuum distillation, cooling after curing
Jan 10, 2018

The reaction is usually carried out with sodium amide and pyridine in the presence of a solvent. Hydrogen evolved during the reaction, while generating aminopyridine sodium derivative, which is hydrolyzed to generate free aminopyridine. Example 1 sodium amide was added to dry toluene, heated to reflux, plus pyridine while purging nitrogen, continue to reflux 6h. The reaction was complete and cooled to 20 ° C. Nitrogen was added and the mixture was slowly added with water. After the addition was completed, the temperature was raised to 60-70 ° C. The toluene layer was allowed to stand for separation. The aqueous layer was kept at 60-70 ° C, extracted twice with toluene, , Collecting 100-140 ° C (8kPa) distillate to give 2-aminopyridine. The yield is 66-70%. Example 2 Toluene was added to a dry stainless steel tank, heated, and toluene was distilled off until the distillate was clear. Cold to below 35 ℃, adding sodium amide. The temperature was raised to 108 ° C and pyridine was added dropwise. Plus Bi, reflux 6h. Add water to 40 ° C and stir for 1 h at 70 ° C. Cool to below 30 ℃, points to the water layer (toluene extraction 1). The toluene layer was dried over anhydrous sodium carbonate. Toluene recovery, solidification and cooling 2-aminopyridine. The yield is 65%. Other methods for the preparation of 2-aminopyridine: 6-aminonicotinic acid is melted and decarboxylated at a temperature above the melting point; Huffman's reaction is carried out from picolinic acid amide; and aminolysis is carried out by 2-bromopyridine. In the industrial production, fresh sodium amide particles and toluene are added to the reactor, and when the mixture is slightly refluxed at 110 ° C, pyridine is dripped under stirring to cool and control the reaction rate; after the reaction is slow, heating and stirring are continued for 3 hours; cooling To 40 ℃ hydrolysis, to react all the dissolved, the hot points to the lower base lye, the oil layer evaporated toluene, vacuum distillation, cooling and solidification, white crystals, the yield of 60% -63%.

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