Synthesis
General procedure for the synthesis of tert-butyl 4-(4-bromopyridin-2-yl)piperazine-1-carboxylate from 4-bromo-2-fluoropyridine and N-BOC-piperazine:
1. 4-Bromo-2-fluoropyridine (1.55 g, 8.81 mmol), N-BOC-piperazine (2.46 g, 13.22 mmol) and potassium carbonate (3.65 g, 26.41 mmol) were suspended in dimethyl sulfoxide (10 mL) in a dry reactor.
2. The reaction mixture was transferred to a sealed tube, heated at 100 °C and stirred overnight.
3. Upon completion of the reaction, the mixture was cooled to room temperature and extracted by adding ethyl acetate and water.
4. The organic layer was separated, washed with brine and subsequently dried over anhydrous magnesium sulfate.
5. The solvent was evaporated under pressure to give the crude product.
6. Purification of the crude product by fast column chromatography (elution gradient: 100% hexane to 1:4 hexane/ethyl acetate) afforded the title compound tert-butyl 4-(4-bromopyridin-2-yl)piperazine-1-carboxylate (2.33 g, 78% yield) as a white solid.
LRMS (m/z): 342/344 [M+1]+.
References
[1] Patent: WO2012/41476, 2012, A1. Location in patent: Page/Page column 60
[2] Bioorganic and Medicinal Chemistry Letters, 2012, vol. 22, # 17, p. 5419 - 5423
[3] Patent: EP2441755, 2012, A1. Location in patent: Paragraph 0176
[4] Patent: EP2489663, 2012, A1. Location in patent: Paragraph 0095; 0096; 0097
