[CH3:1][O:2][C:3]([C:5]1[O:6][C:7]2[CH:13]=[CH:12][C:11]([OH:14])=[CH:10][C:8]=2[CH:9]=1)=[O:4].C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1.O[CH2:35][CH2:36][N:37]1[CH2:41][CH2:40][CH2:39][CH2:38]1.N(C(OC(C)C)=O)=NC(OC(C)C)=O>O1CCCC1>[CH3:1][O:2][C:3]([C:5]1[O:6][C:7]2[CH:13]=[CH:12][C:11]([O:14][CH2:35][CH2:36][N:37]3[CH2:41][CH2:40][CH2:39][CH2:38]3)=[CH:10][C:8]=2[CH:9]=1)=[O:4]Anhydrous tetrahydrofuran (15 ml) was added to a mixture of 5-hydroxybenzofuran-2-carboxylic acid methyl ester (1.10 g, 5.7 mmol), triphenylphosphine (1.50 g, 5.7 mmol), and 1-(2-hydroxyethyl)-pyrrolidine (0.66 g, 5.7 mmol) under a nitrogen atmosphere. Diisopropyl azodicarboxylate (1.15 ml, 5.8 mmol) was slowly added to the solution at room temperature. After 2 days, the solvent was removed and the residue was dissolved in a 2:1 mixture of Et2O:EtOAc (150 ml). The solution was washed with 1.0M aqueous NaOH. The product was extracted into 1.0 M hydrochloric acid and the combined acid extracts were washed with Et2O. The extracts were cooled and the pH of the extracts was adjusted to pH 12 with 50% aqueous NaOH. The basic solution was extracted with CH2Cl2 and the organic layer was dried over anhydrous MgSO4, and concentrated to give 5-(2-pyrrolidin-1-yl-ethoxy)benzofuran-2-carboxylic acid methyl ester (0.96 g) as an amber colored solid.
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