Synthesis
The general procedure for the synthesis of N-Boc-4-(bromoacetyl)piperidine from 1-N-BOC-4-acetylpiperidine was as follows: to a suspension of tert-butyl 4-ethylpiperidine-1-carboxylate (Intermediate B5; 2.87 g, 12.6 mmol) in THF (30 mL) cooled to -78 °C, a THF solution of 1 M bis(trimethylmethylsilyl)lithium amide was slowly added (13.3 mL), and the addition time was controlled within 20 min. The reaction mixture was stirred at -78 °C for 1 h. Trimethylsilyl chloride (1.74 mL, 13.7 mmol) was added. Stirring was continued at 0 °C for 30 min, after which the reaction solution was cooled again to -78 °C and bromine (0.645 mL, 12.6 mmol) was added slowly. After the reaction mixture was naturally warmed to room temperature, the reaction was quenched by pouring into a mixture of 10% Na2S2O3 solution (20 mL) and saturated NH4Cl solution (20 mL). The organic phase was extracted with EtOAc (2×80 mL) and the organic layers were combined, which were treated to afford the target product N-Boc-4-(bromoacetyl)piperidine in a yield of 3.69 g in 96%.
References
[1] Patent: WO2009/150144, 2009, A1. Location in patent: Page/Page column 139
[2] Tetrahedron Letters, 2012, vol. 53, # 7, p. 852 - 853
[3] Bioorganic and Medicinal Chemistry Letters, 2004, vol. 14, # 13, p. 3419 - 3424
[4] Patent: WO2004/41279, 2004, A1. Location in patent: Page/Page column 70
[5] Patent: WO2015/88565, 2015, A1. Location in patent: Paragraph 00214
