Malonic Acid → (2E)-4-Ethyl-2,6-heptadienoic acid

Temperature

100 °C

Allyl bromide (7.1 mL, 81.8 mmol) was added to a mixture of (E)-but-1-enyldiisobutylamine (10.0 g, 54.5 mmol) and acetonitrile (30 mL) at room temperature under a nitrogen atmosphere, and the mixture was then stirred at an external temperature of 70° C. for 17 hours. The reaction mixture was cooled to room temperature and then concentrated under reduced pressure to obtain an iminium salt as a red purple solid. The obtained iminium salt was dissolved in pyridine (100 mL). To the solution, malonic acid (11.3 g, 109.0 mmol) and piperidine (0.81 mL, 8.2 mmol) were then added in this order. The reaction mixture was stirred at an external temperature of 100° C. for 17 hours and then cooled to room temperature. Pyridine was distilled off, and the residue was then separated into aqueous and organic layers by the addition of ethyl acetate and 1 M hydrochloric acid. The organic layer was washed with saturated saline and then dried over anhydrous sodium sulfate. The solvent was distilled off, and the residue was then purified by silica gel chromatography (n-hexane:ethyl acetate=5:1→1:1) to obtain the title compound (6.96 g, yield: 83%) as a colorless oil substance.