Synthesis
General procedure for the synthesis of tert-butyl 4-(4-aminobenzoyl)tetrahydro-1(2H)-pyrazinecarboxylate from tert-butyl 4-(4-nitrobenzoyl)piperazine-1-carboxylate: a mixture of tert-butyl 4-(4-nitrobenzoyl)piperazine-1-carboxylate (20 g, 60 mmol) with 10% Pd/C (4 g) in methanol (600 mL) was subjected to hydrogen (1 atm) atmosphere and the reaction was stirred at room temperature for 18 hours. After completion of the reaction, the reaction mixture was filtered through diatomaceous earth and the filtrate was concentrated under reduced pressure to afford 18 g of tert-butyl 4-(4-aminobenzoyl)piperazine-1-carboxylate as a white solid in 100% yield.
References
[1] Patent: WO2013/177536, 2013, A2. Location in patent: Paragraph 0260
[2] Patent: CN102464631, 2016, B. Location in patent: Paragraph 0094-0096
[3] Patent: WO2018/98275, 2018, A1. Location in patent: Page/Page column 126
[4] Patent: WO2018/98288, 2018, A1. Location in patent: Page/Page column 154; 155
[5] Patent: WO2008/139161, 2008, A1. Location in patent: Page/Page column 161-162
