[OH-].[Na+].C(O)C.C[O:7][C:8](=[O:29])[C:9]1[CH:18]=[C:17]([C:19]2[S:20][CH:21]=[CH:22][CH:23]=2)[C:12]([C:13]([O:15]C)=[O:14])=[CH:11][C:10]=1[C:24]1[S:25][CH:26]=[CH:27][CH:28]=1>O>[S:20]1[CH:21]=[CH:22][CH:23]=[C:19]1[C:17]1[CH:18]=[C:9]([C:8]([OH:29])=[O:7])[C:10]([C:24]2[S:25][CH:26]=[CH:27][CH:28]=2)=[CH:11][C:12]=1[C:13]([OH:15])=[O:14]Sodium hydroxide (4.80 g, 120.0 mmol) is dissolved in water (30 cm3), then ethanol (250 cm3) and 2,5-dithien-2-ylterephthalic acid dimethyl ester (5.30 g, 14.8 mmol) are added. This mixture is heated at 78° C. overnight. The solvent is evaporated under reduced pressure to about half of original volume then water is added. The resultant mixture is neutralized with concentrated hydrochloric acid. The precipitate is collected by filtration and washed with water and ethanol, then dried in vacuo, to yield the product as an off-white solid (4.13 g, 84%). 1H NMR (300 MHz, DMSO-d6): δ(ppm) 13.46 (s, 2H, COOH), 7.72 (s, 2H, Ar—H), 7.70 (dd, J=5.1 and 1.1 Hz, 2H, Ar—H), 7.28 (dd, J=3.6 and 1.1 Hz, 2H, Ar—H), 7.17 (m, 2H, Ar—H); 13C NMR (75 MHz, DMSO-d6): δ(ppm) 168.7 (C═O), 139.7 (q), 134.5 (q), 131.4 (q), 130.2 (CH), 127.9 (CH), 127.5 (CH), 127.1 (CH).
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