The general procedure for the synthesis of methyl 5-methoxy-1H-indole-3-carboxylate from methyl 3,3-dimethoxypropionate and 4-methoxyphenylhydrazine hydrochloride was as follows (Intermediate Example 38): 4-methoxyphenylhydrazine hydrochloride (200 mg) and methyl 3,3-dimethoxypropionate (194 mg) were added to acetic acid (8.0 mL). The reaction mixture was stirred at 70 °C for 4.5 hours. After completion of the reaction, the solvent was removed by concentration under reduced pressure and the residue was purified by column chromatography (eluent: ethyl acetate/hexane, 1:5→1:3) to afford the target product methyl 5-methoxy-1H-indole-3-carboxylate (259 mg, yield: 97%). The product was characterized by 1H NMR (DMSO-d6): δ 3.8 (3H, s), 3.9 (3H, s), 6.8 (1H, dd), 7.4 (1H, d), 7.5 (1H, d), 8.0 (1H, s), 11.8 (1H, brs).ESI/MS (m/z): 204 ([M-H]-).
