Synthesis
General steps:
1. dissolve 60.8 mL of 3-methoxybenzaldehyde in 600 mL of toluene and add 81.9 mL of aminoacetaldehyde dimethyl acetal.
2. Install a Dean-Stark manifold and reflux the reaction mixture for 5 hours, followed by cooling to 5 °C.
3. 209 mL of trifluoroacetic anhydride and 185 mL of boron trifluoride ether compound were slowly added dropwise under nitrogen protection, with the rate of dropwise acceleration controlled to maintain the reaction temperature below 10 °C. The reaction temperature was then increased to 10 °C. The reaction temperature was then increased to 10 °C.
4. After the dropwise addition was completed, the reaction mixture was continued to be stirred at room temperature for 3 days.
5. The reaction mixture was slowly poured into ice water, 250 mL of 2N hydrochloric acid was added, and the organic layer was extracted with 1N hydrochloric acid.
6. Combine the aqueous phases and adjust the pH to 9 with concentrated ammonia.
7. extracted the aqueous phase with ethyl acetate, combined the organic phases, dried and concentrated the solvent under reduced pressure.
8. 66.9 g (84% yield) of 7-methoxyisoquinoline was obtained as a light brown oil.
EI-MS: 159 (M+).
