5-methoxy-isophthalaldehyde can be synthesized from 5-methoxy-1,3-benzyldiethanol and further oxidized to obtain 5-methoxy-isophthalic acid; it can also be prepared by hydrolysis of dimethyl 5-methoxy-isophthalate; or it can be prepared by methanol etherification reaction of 5-hydroxy-isophthalic acid [1]. The reaction formula for the preparation of 5-methoxyisophthalic acid is shown in the figure below:
Reaction formula for the preparation of 5-methoxyisophthalic acid
Method 1,
Take a single-necked reaction flask, weigh dimethyl 5-methoxy-isophthalate and dissolve it in tetrahydrofuran solution, start the stirring device, add 1N hydrochloric acid aqueous solution dropwise. After the addition is complete, the system becomes clear, stir the reaction at room temperature for 4 hours, and detect the reaction progress by thin-layer chromatography. After the reaction is complete, evaporate the reaction solution to dryness, recrystallize the concentrate with acetone, and a white solid precipitates. Filter the solid, wash the filter cake with ethyl acetate, dry the filter cake, and obtain the white solid, which is 5-methoxyisophthalic acid.
Method 2: Take a three-necked reaction flask, prepare a reflux apparatus and a feeding funnel, weigh 5-hydroxyisophthalic acid and dissolve it in 180 mL of methanol, place it in the three-necked reaction flask, start the stirring apparatus, and add concentrated hydrochloric acid dropwise. After the addition is complete, the system becomes clear. Heat the solution to reflux and continue the reflux reaction for 4 hours. Monitor the reaction progress using thin-layer chromatography. After the reaction is complete, remove the oil bath, cool the reaction solution, and evaporate the reaction solution to dryness. Recrystallize the concentrate from acetone; a white solid precipitates. Filter the solid, wash the filter cake with ethyl acetate, and dry the filter cake to obtain the white solid, which is 5-methoxyisophthalic acid.
