[NH2:1][C:2]1[CH:13]=[CH:12][C:5]2[O:6][C:7]3([C:10](=[O:11])[C:4]=2[CH:3]=1)[CH2:9][CH2:8]3.C(=O)([O-])[O-].[Ca+2].[Br:19]Br>C(Cl)(Cl)(Cl)Cl.C(Cl)Cl>[NH2:1][C:2]1[CH:13]=[CH:12][C:5]2[O:6][C:7]3([C:10](=[O:11])[C:4]=2[C:3]=1[Br:19])[CH2:9][CH2:8]35-Aminospiro[benzo[b]furan-2(3H),1'-cyclopropane]-3-one (0.747 g.) and calcium carbonate (0.47 g.) were suspended in a mixture of carbon tetrachloride (20 ml.) and methylene chloride (5 ml.). The suspension was cooled to -17° C., then bromine (0.22 ml.) was added thereto dropwise, followed by stirring for 45 minutes. The reaction mixture was poured into ice-water, then extracted with ethyl acetate. The extract was washed with water and dried. The solvent was evaporated off, and the residue was recrystallized from ethanol-water. By the above procedure there was obtained 5-amino-4-bromospiro[benzo[b]furan-2(3H),1'-cyclopropane]-3-one as yellow needles melting at 167°-170° C. Yield 0.6 g.
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