Synthesis
Step 2C: Preparation of 2,8-dibromoquinoline: 8-bromo-1H-2-quinolinone (5 g, 22 mmol) was mixed with phosphorus tribromide (13 g, 45 mmol), heated to 140 °C and reacted for 3 hours. After completion of the reaction, the mixture was slowly poured into a pre-prepared ice-water mixture (100 g ice with 100 mL water). After continuous stirring for 1 h, the precipitated solid was collected by filtration to afford the target product 2,8-dibromoquinoline (5.1 g, 80% yield). The product was confirmed by mass spectrometry analysis (APCI+ mode), detecting m/z 286, 288, and 290 (corresponding to [M+1]+ peaks for different combinations of bromine isotopes).
References
[1] Tetrahedron Letters, 2005, vol. 46, # 48, p. 8419 - 8422
[2] Journal of Medicinal Chemistry, 2009, vol. 52, # 3, p. 868 - 877
[3] Patent: WO2008/124323, 2008, A1. Location in patent: Page/Page column 29
[4] Patent: WO2008/121687, 2008, A2. Location in patent: Page/Page column 28
[5] Organometallics, 2018, vol. 37, # 16, p. 2760 - 2768
