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To a mixture of 3,5-dimethoxybenzaldehyde (500 g, 3 mol) and p-hydroxyphenyl acetic acid (457 g, 3 mol) was added acetic anhydride (1 L) and triethylamine (420 mL). This non-homogeneous mixture on heating becomes homogeneous at ˜70° C. After being stirred at 130–140° C. for 6 h, the mixture was cooled to room temperature. Concentrated HCl (1 L) was added to the reaction mixture slowly in 50 min keeping temp between 20–30° C. The light yellow precipitate obtained was filtered and rinsed with Dl water in the Buchner funnel. The solid was dissolved in 3N NaOH (5 L ) and stirred for 1 h and filtered. The filtrate was acidified, maintaining a temperature at 25–30° C., with conc. HCl to pH 1. The precipitated product was filtered and washed with water to give crude product. The crude product was recrystallized from MeOH-H2O then dried at 40° C. for 6 h. Yield: pale yellow solid 428 g (47%). 1HNMR (DMSO-d6): δ12.48 (br, 1H), 9.42 (s, 1H), 7.59 (s, 1H), 6.95 (d, J=8.0 Hz, 2H), 6.76 (d, J=8.0 Hz, 2H), 6.35 (t, J=2.2 Hz, 1H), 6.27 (d, J=2.2 Hz, 2H), 3.56 (s, 6H).

1. temperatureThis non-homogeneous mixture on heating
2. custombecomes homogeneous at ˜70° C
3. custombetween 20–30° C
4. customThe light yellow precipitate obtained
5. filtrationwas filtered
6. washrinsed with Dl water in the Buchner funnel
7. dissolutionThe solid was dissolved in 3N NaOH (5 L )
8. stirringstirred for 1 h
9. filtrationfiltered
10. temperaturemaintaining a temperature at 25–30° C.
11. filtrationThe precipitated product was filtered
12. washwashed with water
13. customto give crude product
14. customThe crude product was recrystallized from MeOH-H2O
15. customthen dried at 40° C. for 6 h