[CH:1]([C:3]1[CH:4]=[C:5]([CH:10]=[C:11]([N:13]2[CH:17]=[CH:16][CH:15]=[CH:14]2)[CH:12]=1)[C:6]([O:8][CH3:9])=[O:7])=O.C(O)(=O)[CH2:19][C:20]([OH:22])=[O:21].N1CCCCC1.N1C=CC=CC=1>O>[C:20](/[CH:19]=[CH:1]/[C:3]1[CH:4]=[C:5]([CH:10]=[C:11]([N:13]2[CH:17]=[CH:16][CH:15]=[CH:14]2)[CH:12]=1)[C:6]([O:8][CH3:9])=[O:7])([OH:22])=[O:21]A mixture of methyl 3-formyl-5-(pyrrol-1-yl)benzoate (3.0 g), malonic acid (2.73 g), piperidine (0.3 ml) and pyridine (30 ml) was stirred for 1 hour at 80° C. After being cooled to room temperature, the reaction mixture was poured into water. The solution was acidified to pH 1 and extracted with ethyl acetate. The extract was washed with water and brine and dried over magnesium sulfate. The solvent was evaporated in vacuo and the residue was purified by column chromatography on silica gel eluting with the mixture of chloroform and methanol (15:1). The eluted fractions containing the desired product were collected and evaporated in vacuo to give methyl 3-((E)-2-carboxyethenyl)-5-(pyrrol-1-yl)benzoate (2.43 g).
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