[NH:1]1[C:9]2[C:4](=[CH:5][CH:6]=[CH:7][CH:8]=2)[C:3]2([CH2:13][CH2:12][CH2:11][CH2:10]2)[C:2]1=[O:14].C([O-])(=O)C.[Na+].[Br:20]Br.C(=O)([O-])O.[Na+]>C(O)(=O)C>[Br:20][CH:13]1[C:3]2([C:4]3[C:9](=[CH:8][CH:7]=[CH:6][CH:5]=3)[NH:1][C:2]2=[O:14])[CH2:10][CH2:11][CH2:12]1A solution of spiro[cyclopentane-1,3′-[3H]indol]-2′(1′H)-one (0.27 g, 1.4 mmol) and sodium acetate (0.12 g, 1.46 mmol) in acetic acid (10 cm3) was treated with bromine (0.24 g, 1.51 mmol) in acetic acid (2 cm3). After 30 min. the mixture was poured into sat. sodium hydrogen carbonate solution and extracted with EtOAc (×2), the combined organic layers were washed with water, sat. sodium hydrogen carbonate solution, water, dried (MgSO4), and evaporated to give the subtitled compound (0.37 g, 1.47 mmol, 96%) as an off-white solid which was used without further purification: 1H NMR (CDCl3) δ 1.8-2.27 (m, 8H), 6.79 (d, J=8 Hz, 1H), 7.30-7.39 (m, 2H), 8.63 (br s, 1H).
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