Synthesis
S3: In a 10L four-necked flask equipped with a mechanical stirrer and a thermometer, N-Boc-4-(cyclopropylmethyl)piperazine (2.00 kg, 8.32 mol) and 5 kg of isopropanol were added and heated up to 40 °C. Concentrated hydrochloric acid (2.04 kg, 20.80 mol) was slowly added dropwise, and the reaction temperature was controlled between 40°C and 50°C. After the dropwise addition, the reaction was maintained at 40°C to 50°C with stirring for 4 hours. Upon completion of the reaction, the reaction solution was concentrated to remove most of the isopropanol and cooled to 0 °C. The pH of the residue was adjusted to 10-11 with 5 mol/L aqueous sodium hydroxide. extraction was carried out with dichloromethane (5L x 3), the organic phases were combined and washed once with 5 kg of saturated aqueous sodium chloride. The organic phase was diluted with dichloromethane to give 1.11 kg of a light yellow liquid 1-cyclopropylmethylpiperazine in 94% yield. The NMR spectrum of the product was consistent with the standard spectrum.
References
[1] Patent: CN108341792, 2018, A. Location in patent: Paragraph 0030; 0035
[2] Journal of Medicinal Chemistry, 2004, vol. 47, # 11, p. 2833 - 2838
[3] Patent: EP2481739, 2012, A1. Location in patent: Page/Page column 68
[4] Patent: WO2018/5860, 2018, A1. Location in patent: Page/Page column 172; 201; 203
