反应详情

温度

-55 °C

The starting material (a) was prepared as described in J. Org. Chem. 2000, 65, 6984-6991. cis-5-Norbornene-exo-2,3-dicarboxylic anhydride (5 g, 30.45 mmol) was suspended in a 1:1 mixture of toluene and carbon tetrachloride (610 mL). The mixture was stirred for 10 min. Quinine (10.87 g, 33 5 mmol) was added and the flask was degassed and backfilled with nitrogen. The solution was cooled to −55° C. While stirring, methanol (3.7 mL, 91.35 mmol) was added. The mixture was stirred at −55° C. for 16 h. Upon warming to 25° C., the mixture was concentrated in vacuo to a foam. The foam was dissolved in a mixture of ethyl acetate (400 mL) and 1.0 M aqueous hydrochloric acid solution (400 mL). The layers were separated and the organic layer was further washed with 1.0 M aqueous hydrochloric acid solution (2×200 mL), saturated aqueous brine solution (100 mL) and dried over magnesium sulfate, filtered, and concentrated in vacuo to afford the desired product, (1S,2S,3R,4R)-3-(methoxycarbonyl)bicyclo[2.2.1]hept-5-ene-2-carboxylic acid (5.95 g, 30.3 mmol, 99%), as a clear oil. 1H NMR (400 MHz, DMSO-d6) δ: 1.31 (1H, d, J=8.5 Hz), 1.98 (1H, d, J=8.6 Hz), 2.51 (2H, d, J=1.6 Hz), 2.95 (2H, bs), 3.52 (3H, s), 6.17-6.21 (2H, m), 12.16 (1H, s).

1. customthe flask was degassed
2. stirringWhile stirring
3. stirringThe mixture was stirred at −55° C. for 16 h
4. temperatureUpon warming to 25° C.
5. concentrationthe mixture was concentrated in vacuo to a foam
6. dissolutionThe foam was dissolved in a mixture of ethyl acetate (400 mL) and 1.0 M aqueous hydrochloric acid solution (400 mL)
7. customThe layers were separated
8. washthe organic layer was further washed with 1.0 M aqueous hydrochloric acid solution (2×200 mL), saturated aqueous brine solution (100 mL)
9. dry with materialdried over magnesium sulfate
10. filtrationfiltered
11. concentrationconcentrated in vacuo