98895-60-4

372-09-8

1489-69-6

98895-60-4

2.6.6 Synthesis of 2-cyano-3-cyclopropylpropenoic acid (23): To a solution of cyclopropanecarboxaldehyde (0.36 g, 5.25 mmol) in anhydrous toluene (10 mL) under anhydrous conditions were sequentially added cyanoacetic acid (0.44 g, 5.25 mmol), piperidine (1.0 mL, 10.5 mmol) and glacial acetic acid (1.2 mL, 20.9 mmol). The reaction mixture was stirred in an oil bath at 80 °C for 2 h and subsequently cooled to room temperature. After completion of the reaction, the excess solvent was removed by rotary evaporator under reduced pressure. The residue was dissolved in ethyl acetate (20 mL) and the organic layer was washed sequentially with 1 M aqueous hydrochloric acid (10 mL) and deionized water (10 mL). The organic layer was dried over anhydrous sodium sulfate, filtered and concentrated to obtain the crude product. The crude product was purified by silica gel column chromatography with dichloromethane/methanol (98/2, v/v) as eluent, and the target component was collected and concentrated to give 2-cyano-3-cyclopropylpropenoic acid (23) 0.35 g as a white solid in 49% (2.55 mmol) yield.