Synthesis
Step 2: tert-Butyl (S)-4-benzyl-3-methylpiperazine-1-carboxylate (11.6 g, 40 mmol) was dissolved in dichloromethane (100 mL), trifluoroacetic acid (20 mL) was added slowly and the reaction mixture was stirred at room temperature for 30 minutes. Upon completion of the reaction, the reaction solution was concentrated to remove the solvent. Subsequently, the concentrate was dissolved in ice water and concentrated sodium hydroxide solution was added in batches to adjust the pH to above 13. The aqueous phase was extracted with ethyl acetate, the organic phases were combined, dried with anhydrous sodium sulfate, filtered and concentrated to afford (S)-1-benzyl-2-methylpiperazine (6.84 g, 90% yield), which could be used in the next reaction without further purification. Mass spectrum (ESI) m/z: 191.2 [M+H]+.
References
[1] Organic Letters, 2008, vol. 10, # 7, p. 1473 - 1476
[2] Patent: US2004/132711, 2004, A1. Location in patent: Page/Page column 16-17
[3] Patent: EP2952510, 2015, A1. Location in patent: Paragraph 0133
[4] Patent: US2009/270336, 2009, A1. Location in patent: Page/Page column 11-12
[5] Patent: US2005/261310, 2005, A1. Location in patent: Page/Page column 12-13; 29
