Triphenylphosphine → 3-Methyl-4-(piperidin-3-ylmethoxy)-benzofuran-2-carboxylic acid ethyl ester

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A solution of 4-hydroxy-3-methyl-benzofuran-2-carboxylic acid ethyl ester (1 g), 3-(hydroxymethyl)piperidine (661 μl), triphenylphosphine (1.55 g) and azodicarboxylic acid diethyl ester (930 μl) in THF (20 ml) was stirred overnight at room temperature. A white precipitate separated out. The precipitate was filtered out and the filtrate was evaporated to dryness. The residue was separated by silica gel column chromatography developed by dichloromethane-methanol to give 3-methyl-4-(piperidin-3-ylmethoxy)-benzofuran-2-carboxylic acid ethyl ester (1.1 g) as a colorless oil. FAB-MS: m/z 318 (MH+); 1H-NMR (CDCl3): δ 1.42-2.02 (4H, m), 1.43 (3H, t, J=7 Hz), 2.43 (1H, m), 2.74 (2H, m), 2.75 (3H, s), 3.34 (1H, br d, J=12 Hz), 3.49 (1H, br d, J=12 Hz), 3.96 (1H, dd, J1=9 Hz, J2=6 Hz), 4.02 (1H, dd, J1=9 Hz, J2=5 Hz), 4.43 (2H, q, J=7 Hz), 6.59 (1H, d, J=8 Hz), 7.13 (1H, d, J=8 Hz), 7.30 (1H, t, J=8 Hz).

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