[CH:1]([C:3]1[Se:7][C:6]([C:8]([O:10]C)=[O:9])=[CH:5][CH:4]=1)=[O:2].[OH-:12].[Na+].Cl>O.[N+]([O-])([O-])=O.[Ag+]>[Se:7]1[C:6]([C:8]([OH:10])=[O:9])=[CH:5][CH:4]=[C:3]1[C:1]([OH:2])=[O:12]A solution of silver nitrate (6.26 g, 36.86 mmol) in water (10 mL) was added to methyl 5-formylselenophene-2-carboxylate (4.0 g, 18.43 mmol) at 0° C. for 5 min. Then a solution of sodium hydroxide (3.05 g, 76.34 mmol) in water (10 mL) was added to the reaction mixture at the same temperature for 5 min and stirred the mixture at room temperature (rt) for 1 h. The cooled reaction mixture was poured into ice cooled water and acidified with dil. HCl. The solution was extracted with ethyl acetate (3×100 mL) and the combined organic layer was washed with water, brine and dried over sodium sulfate. The solution was filtered and evaporated the solvent to give the product as off-white color solid (3.2 g, 80%), mp 293-295° C. 1H NMR (400 MHz, DMSO-d6): δ 13.48 (2H, br s, 2×—COOH), 7.82 (2H, s, H-3,4); LC-MS (negative ion mode): m/z 219, 217 (M−H)−.
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