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4-Cyclopropanoylpiperazine-1-carboxylic Acid tert-Butyl Ester is a useful reagent for organic synthesis and other chemical processes. It is used as a reagent in the preparation of propanoyl-quinazolinone scaffold-based novel PARP1 inhibitors.

S1: In a 20L four-necked flask equipped with a mechanical stirrer and a thermometer, N-Boc-piperazine (1.82 kg, 9.77 mol), triethylamine (1.48 kg, 14.66 mol), and dichloromethane (5.46 kg) were added, and the mixture was cooled to 0 °C. Cyclopropanecarbonyl chloride (1.12 kg, 10.75 mol) was slowly added dropwise while maintaining the temperature from 0 °C to 10 °C. After the dropwise addition was completed, the reaction mixture was stirred at 10°C to 20°C for 3 hours. After completion of the reaction, 5 kg of water was added and the pH was adjusted to 8-9 with sodium carbonate. the organic and aqueous phases were separated and the organic phase was collected. Extract again with 1.50kg of aqueous phase and combine all dichloromethane phases. The combined organic phases were washed sequentially with 2 kg of 0.05 M dilute hydrochloric acid and 2 kg of water. The dichloromethane phase was concentrated to give tert-butyl 4-(cyclopropanecarbonyl)piperazine-1-carboxylate (2.43 kg, 98% yield). The NMR spectrum was consistent with the standard spectrum.

[1] Patent: CN108341792, 2018, A. Location in patent: Paragraph 0028; 0033
[2] Patent: US2010/35883, 2010, A1. Location in patent: Page/Page column 56
[3] Patent: WO2011/130661, 2011, A1. Location in patent: Page/Page column 102
[4] Patent: US2004/14770, 2004, A1. Location in patent: Page/Page column 11