Hydrochloric Acid → 2-Benzylacrylic Acid

To a cooled (0° C.) mixture of benzyl malonic acid (3.37 g, 17.4 mmol) and diethylamine (1.34 g, 18.3 mmol) in water (10 ml) was added formaldehyde (37% solution in water, 2.1 g, 26.1 mmol) with stirring. The reaction was allowed to warm to room temperature and after 2 hours heated to reflux. After 16 hours, the reaction mixture was cooled to room temperature, then made acidic with hydrochloric acid. The mixture was extracted twice with ethyl acetate. The ethyl acetate layers were combined and dried over sodium sulfate, then the solvent was removed under reduced pressure. The resulting residue was purified by column chromatography to yield 2.2 g (78%) of white solid. 1H NMR (CDCl3): δ 3.7 (s, 2H), 5.6 (s, 1H) , 6.4 (s, 1H) , 7.1-7.4 (m, 5H)