反应详情

To a 250 mL of two-necked round-bottom (RB) flask containing (−) citronellal (25.0 g, 163 mmol) in 50 mL of ethanol under argon was added the catalyst of 3-ethyl-5-(2-hydroxyethyl)-4-methylthiazolium bromide (4.1 g, 16.3 mmol) and triethylamine (17.0 mL, 120 mmol). The mixture was then heated to reflux over night. After removal of the solvent under reduced pressure, the resulted mixture was poured into 100 mL of water and extracted by ethyl ether (3×60 mL). The combined organic layer was dried over anhydrous MgSO4 and concentrated under vacuum. The residue was purified by flash chromatography on silica gel (hexane:ethyl acetate=20:1, v/v) to afford 18.5 g of product as a colorless oil (yield: 75%). 1H NMR (400 MHz, CDCl3) δ 5.08 (m, 2H), 4.15 (m, 1H), 3.47 (dd, 1H, J=5.04 Hz), 2.40 (m, 1H), 2.2 (m, 1H), 1.9-2.1 (m, 6H), 1.60 (d, 12H), 1.1-1.3 (m, 4H), 0.8-1.0 (m, 6H). 13C NMR (400 MHz, CDCl3) δ 212.63, 131.63, 131.30, 124.52, 124.40, 124.00, 75.59, 74.70, 45.16, 45.15, 41.15, 41.00, 37.95, 36.85, 36.83, 35.56, 29.36, 29.04, 28.92, 28.81, 25.65, 25.42, 25.39, 25.36, 25.22, 20.29, 19.82, 19.65, 18.46, 17.60.

1. temperatureThe mixture was then heated
2. temperatureto reflux over night
3. customAfter removal of the solvent under reduced pressure
4. additionthe resulted mixture was poured into 100 mL of water
5. extractionextracted by ethyl ether (3×60 mL)
6. dry with materialThe combined organic layer was dried over anhydrous MgSO4
7. concentrationconcentrated under vacuum
8. customThe residue was purified by flash chromatography on silica gel (hexane