2-Chlorobenzaldehyde → 3-(2-Chlorophenyl)acrylic acid

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A mixture of 18.4 g (0.19 mol) of potassium acetate in 70.3 g (0.5 mol) 2-chlorobenzaldehyde is heated to 145° C. Next 76.5 g (0.75 mol) of acetic anhydride is added in 1 hour. After dosing of 0.50 mol of acetic anhydride the mixture became clear. The mixture is stirred at 145° C. during 18 hours. The hot reaction mixture is poured into a mixture of 670 g of 6.4 w/w % aqueous NaOH (1.1 mol, 2.1 eq based on 2-chlorobenzaldehyde) and 200 mL toluene at 80° C. The final pH was 7.4. After separation of the organic phase, the water layer is again extracted with 100 mL of toluene at 80° C. The combined water phases are acidified with 380 g of 25 w/w % H2SO4 to pH 4.6. Crystallization starts at pH 6.4. The mixture is cooled to 25° C. and the product is isolated by filtration, washed with 100 mL of water and dried (vacuo, 50° C.). 3-(2-chloro-phenyl)-acrylic acid was obtained as an off white solid (100.2 g, 0.55 mol, yield 55%).

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