C([O:3][C:4]([C:6]1[S:15][C:14]2[C:13]3[CH:16]=[C:17]([Br:20])[CH:18]=[CH:19][C:12]=3[O:11][CH2:10][CH2:9][C:8]=2[CH:7]=1)=[O:5])C.[OH-].[Na+].CCO>C1COCC1.O>[Br:20][C:17]1[CH:18]=[CH:19][C:12]2[O:11][CH2:10][CH2:9][C:8]3[CH:7]=[C:6]([C:4]([OH:5])=[O:3])[S:15][C:14]=3[C:13]=2[CH:16]=1To a stirred suspension of 9-bromo-4,5-dihydro-6-oxa-1-thia-benzo[e]azulene-2-carboxylic acid ethyl ester (4.24 g; 12 mmol) in THF (40 ml) at room temperature was added a solution of NaOH (0.96 g; 24 mmol) in water (20 ml) followed by EtOH (20 ml). The reaction mixture was stirred at room temperature for 4 h (now a clear solution) upon which time it was quenched with 2M HCl (20 ml) and diluted with water (50 ml). The resulting solid was collected by filtration, washed with water and dried to give 9-bromo-4,5-dihydro-6-oxa-1-thia-benzo[e]azulene-2-carboxylic acid as a white solid (3.64 g; 93%). δH (400 MHz, d6-DMSO) 3.22 (t, J=5.2, 2H), 4.31 (t, J=5.2, 2H), 7.02 (d, J=8.4, 1H), 7.43 (dd, J=8.4 and 2.4, 1H), 7.62 (s, 1H), 7.78 (d, J=2.4, 1H).
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