Synthesis
1-Fluoro-4-nitrobenzene (5 g, 35.43 mmol) and N-BOC-piperazine (6.6 g, 35.43 mmol) were dissolved in N,N-dimethylformamide (DMF, 100 mL) and potassium carbonate (14.7 g, 106.29 mmol) was added as a base. The reaction mixture was stirred at 50 °C for 18 hours. Upon completion of the reaction, the mixture was cooled to room temperature and subsequently concentrated under reduced pressure to remove the solvent. The oily residue obtained was washed three times with ether to purify the product. The final product was obtained as tert-butyl 4-(4-nitrophenyl)piperazine-1-carboxylate as a yellow solid (8.2 g, 95% yield). The product was confirmed by 1H NMR (400 MHz, chloroform-d): δ 1.48 (s, 9H), 3.38-3.45 (m, 4H), 3.56-3.63 (m, 4H), 6.75-6.86 (m, 2H), 8.07-8.20 (m, 2H). Mass spectrometry (MS) analysis showed m/z 308.1 ([M+H]+), consistent with the expected molecular formula C15H21N3O4.
References
[1] Patent: WO2006/38039, 2006, A1. Location in patent: Page/Page column 17; 30
[2] Patent: WO2017/123542, 2017, A1. Location in patent: Page/Page column 398; 399
[3] Patent: CN106905245, 2017, A. Location in patent: Paragraph 0314; 0315; 0316; 0317; 0318
[4] Patent: US2003/13708, 2003, A1
[5] Patent: US2004/87575, 2004, A1
