Hydroxyphenylacetic acid → 3-(3,5-Dimethoxyphenyl)-2-(4-hydroxyphenyl)-acrylic acid

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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): δ 12.48(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).

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