O=[C:2]1[C:11]2[C:6](=[CH:7][C:8]([C:12]([OH:14])=[O:13])=[CH:9][CH:10]=2)[C:5](=[O:15])[NH:4][NH:3]1.P(Br)(Br)(Br)(Br)[Br:17]>ClCCCl.CC(O)=O>[Br:17][C:2]1[C:11]2[C:6](=[CH:7][C:8]([C:12]([OH:14])=[O:13])=[CH:9][CH:10]=2)[C:5](=[O:15])[NH:4][N:3]=11,4-Dioxo-1,2,3,4-tetrahydro-phthalazine-6-carboxylic acid (91.0 g, 0.44 mol) was suspended in DCE (1.0 L) and phosphorus pentabromide (761.0 g, 1.77 mol) was added in three portions and the reaction heated to reflux for 24 hours. The reaction was cooled to RT and poured onto ice (2.5 kg) and the resulting precipitate filtered and washed with water to give the crude product (130.0 g). This crude material was suspended in HOAc (1.6 L) and heated to 125° C. for 2 h. The reaction was cooled to RT and poured onto ice (1.5 kg) and the resulting precipitate filtered. The solid was washed with water and dried to give the title compound (85 g, 73% yield) as a yellow solid. Tr=0.94 min, m/z (ES+) (M+H)+ 310 & 312
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