[Synthesis]
Step 1. Preparation of 2-[1-(2-thiophene)ethylidene]malononitrile: 2-Acetylthiophene (500 mg, 3.96 mmol), malononitrile (300 mg, 4.75 mmol), ammonium acetate (915 mg, 12 mmol) and acetic acid (0.7 mL, 12 mmol) were dissolved in toluene (20 mL). The reaction mixture was refluxed for 16 hours. After completion of the reaction, the mixture was poured into ethyl acetate and washed sequentially with water and 1 M HCl aqueous solution. The organic layers were combined, dried with anhydrous magnesium sulfate and concentrated under reduced pressure. The residue was purified by column chromatography (n-hexane:ethyl acetate=5:1) to give 350 mg (51% yield) of 2-[1-(2-thiophene)ethylidene]malononitrile as a brown oil.1H NMR (400 MHz, CDCl3) δ: 8.05 (d, J=4.0 Hz, 1H), 7.80 (d, J=4.8 Hz, 1H), 7.80 ( t, J=4.4 Hz, 1H), 2.71 (s, 3H).
Step 1. Preparation of 2-[1-(2-thiophene)ethylidene]malononitrile: 2-acetylthiophene (20 g, 0.1 mol), malononitrile (12.6 g, 0.19 mol), ammonium acetate (36.6 g, 0.48 mol) and acetic acid (27.2 mL, 0.48 mol) were dissolved in toluene (120 mL). The reaction mixture was refluxed for 18 hours. After completion of the reaction, the mixture was poured into ethyl acetate and washed sequentially with water and 1 N HCl aqueous solution. The organic layers were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by column chromatography (n-hexane:ethyl acetate=3:1) to give 20.8 g (75% yield) of 2-[1-(2-thiophene)ethylidene]malononitrile as a brown solid.1H NMR (400 MHz, CDCl3) δ: 8.05 (d, J=4.0 Hz, 1H), 7.80 (d, J=4.8 Hz, 1H), 7.80 (t , J=4.4 Hz, 1H), 2.71 (s, 3H). |
[References]
[1] Heterocyclic Communications, 2014, vol. 20, # 1, p. 25 - 31
[2] Bulletin of the Chemical Society of Japan, 1988, vol. 61, p. 1375 - 1378
[3] Tetrahedron, 2006, vol. 62, # 49, p. 11311 - 11319
[4] Patent: WO2007/102679, 2007, A1. Location in patent: Page/Page column 26; 33
[5] Organic Letters, 2013, vol. 15, # 20, p. 5298 - 5301 |