C([O-])(=O)C.[Na+].C([CH2:9][CH2:10][N:11]1[CH:15]=[C:14]([C:16]2[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=2)[CH:13]=[C:12]1[C:22]([OH:24])=O)(O)=O>C(OC(=O)C)(=O)C>[C:16]1([C:14]2[CH:13]=[C:12]3[N:11]([CH2:10][CH2:9][C:22]3=[O:24])[CH:15]=2)[CH:17]=[CH:18][CH:19]=[CH:20][CH:21]=1Anhydrous sodium acetate (200 mg, 2.5 mmol) was added to a stirred solution of 1-(2-carboxyethyl)-4-phenyl-pyrrole-2-carboxylic acid (1.0 g, 3.90 mmol) in acetic anhydride (10 mL) and heated at reflux for 16 h. Excess acetic anhydride was evaporated in vacuo and water was added. The mixture was extracted with ethyl acetate and the separated organic layer was washed with water, brine, dried over anhydrous sodium sulfate, filtered and concentrated in vacuo to afford the crude product. Purification by column chromatography over neutral alumina using 25% ethyl acetate in petroleum ether as eluent afforded 6-phenyl-2,3-dihydropyrrolizin-1-one (200 mg, 27%) as a brown solid.
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