C[O:2][C:3]([C:5]1[N:6]([CH2:11][C:12]([C:14]2[CH:19]=[CH:18][C:17]([O:20][CH3:21])=[CH:16][CH:15]=2)=O)[C:7]([Br:10])=[CH:8][CH:9]=1)=O.C([O-])(=O)C.[NH4+:26].O>C(O)(=O)C.O1CCOCC1>[Br:10][C:7]1[N:6]2[CH:11]=[C:12]([C:14]3[CH:19]=[CH:18][C:17]([O:20][CH3:21])=[CH:16][CH:15]=3)[NH:26][C:3](=[O:2])[C:5]2=[CH:9][CH:8]=1A mixture of 5-bromo-1-[2-(4-methoxy-phenyl)-2-oxo-ethyl]-1H-pyrrole-2-carboxylic acid methyl ester (0.15 g, 0.43 mmol) and ammonium acetate (170 mg, 2.21 mmol) in glacial acetic acid (2 mL) was heated at 130° C. overnight. The reaction was stopped, and the recovered starting material was suspended in 1,4-dioxane (2 mL), treated with ammonium acetate (170 mg, 2.21 mmol) and then was heated in a sealed tube at 120° C. for 5 h. At this time, the reaction was treated with additional ammonium acetate, and the mixture continued stirring at 120° C. overnight. At this time, the reaction was treated with water. The resulting precipitate was collected by filtration, washed with water (2×) and dried in vacuo to afford 6-bromo-3-(4-methoxy-phenyl)-2H-pyrrolo[1,2-a]pyrazin-1-one (78 mg, 55%) as red solid. 1H NMR (DMSO-d6) δ ppm 7.54-7.63 (m, 4H), 7.03 (d, J=9.0 Hz, 2H), 6.96 (d, J=1.3 Hz, 1H), 3.80 (s, 3H). LC-MS calcd. for C14H12BrN2O2 [(M+H)+] 319, obsd. 319.0.
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