P(Br)(Br)([Br:3])=O.[N:6]1[C:7]2[N:8]([C:13]3[CH:19]=[CH:18][CH:17]=[CH:16][C:14]=3[N:15]=2)[CH:9]=[CH:10][C:11]=1O>ClCCCl.CN(C=O)C>[Br:3][C:11]1[CH:10]=[CH:9][N:8]2[C:13]3[CH:19]=[CH:18][CH:17]=[CH:16][C:14]=3[N:15]=[C:7]2[N:6]=1Phosphorus oxybromide (25 g, 87 mmol) was added to a suspension of benzo[4,5]imidazo[1,2-a]pyrimidin-2-ol (5.2 g, 28.1 mmol) in DCE (Ratio: 1.000, Volume: 93 ml) and DMF (Ratio: 0.01, Volume: 0.927 ml). Heated the reaction mixture to 100° C. for 3 hours. Cooled the reaction to room temperature and concentrated. Diluted with ice water and quenched to pH ˜8 with concentrated ammonium hydroxide. The resulting residue was filtered and washed with water followed by ethyl ether. Dried under vacuum to afford crude 2-bromobenzo[4,5]imidazo[1,2-a]pyrimidine (6.97 g, 28.1 mmol, 100% yield).
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