p-Toluenesulfonic acid monohydrate → Hydroxy-[2-(4-methoxy-phenyl)-6-methyl-imidazo[1,2-a]pyridin-3-yl]-acetic acid ethyl ester

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Reaction Steps

To a magnetically stirred solution of 2-(4-methoxy-phenyl)-6-methyl-imidazo[1,2-a]pyridine 13a (2.55 g, 10.71 mmol) and ethyl glyoxylate toluene solution (11.79 mL, 54.62 mmol) in toluene (130 mL) under Ar atmosphere was added p-toluenesulfonic acid monohydrate (60.9 mg, 0.32 mmol). The reaction mixture was equipped with a dean-stark trap and refluxed for 4 h. The mixture was cooled to room temperature and concentrated in vacuo. The crude product was purified by column chromatography over silica gel (40:60 EtOAc/hexane, then 100% EtOAc as eluent), which gave the title compound (0.72 g, 20%) as an off white solid. 1H NMR (400 MHz, CDCl3) δ 1.15 (t, J=7.0 Hz, 3H), 2.31 (s, 3H), 3.83 (s, 3H), 4.13 (m, 1H), 4.24 (m, 1H), 5.75 (s, 1H), 6.91 (d, J=8.8 Hz, 2H), 7.04 (dd, J=1.4, 9.1 Hz, 1H), 7.47 (d, J=9.1 Hz, 1H), 7.60 (d, J=8.8 Hz, 2H), 7.99 (s, 1H).

Provenance & Evidence