Synthesis
At a temperature lower than 40°C, 48L of deionized water was added to a 300L stainless steel reactor, and 48kg of sodium hydroxide was added under slow stirring until completely dissolved. Subsequently, 16 kg of 2-amino-3-hydroxypyridine, 1.6 kg of tetrabutylammonium bromide, and 17.92 L of benzyl chloride were added sequentially to the sodium hydroxide solution. The reaction mixture was heated to 70~75°C and kept at this temperature for 6 hours. When the reaction was completed, stirring was stopped and the mixture was left to stratify. The aqueous phase was extracted with toluene (20L x 3) and the combined organic phases were washed with pure water (30L x 2). The organic phase was concentrated until a large amount of solid precipitated, followed by crystallization at 0~5°C and stirring for 2 hours. Upon completion of crystallization, centrifugation was performed and the filter cake was washed with 3.2 L of pre-cooled toluene. Finally, it was dried under vacuum at 50~55°C for 3 h to give 22.5 kg of bright yellow solid Intermediate II (2-amino-3-benzyloxypyridine) in 77.3% molar yield and 99.53% purity.
References
[1] Chemistry Letters, 2006, vol. 35, # 3, p. 270 - 271
[2] Synthesis, 1981, # 12, p. 971 - 973
[3] Patent: CN107311998, 2017, A. Location in patent: Paragraph 0035-0036
[4] Journal of Chemical Research, Miniprint, 1986, # 11, p. 3368 - 3390
[5] Patent: CN103570683, 2018, B. Location in patent: Paragraph 0927; 0928; 0930; 0931
