反应详情

2 Dibromomethane (6.13 g) and zinc dust (6.92 g) were added to dry tetrahydrofuran (100 ml), and the resulting mixture was cooled to 0°~5° C. A dichloromethane solution (25.9 ml) of 1M titanium tetrachloride was added to the tetrahydrofuran solution in about 10 min, and the resulting mixture was allowed to react for 4 days at 0°~5° C. Then a solution of (RS)-4-tert-butyldimethylsilyloxy-3-methyl-2-(2-propenyl)cyclopent-2-ene-1-one (6.27 g) in dichloromethane (30 ml) was added at 0°5° C. in about 10 min. After the mixture was allowed to react for 12 hours at the same temperature, the reaction mixture was diluted with pentane (150 ml), and then a slurry consisting of sodium bicarbonate (150 g) and water (80 ml) was slowly added. After stirring for 2 hours at the same temperature, the reaction mixture was filtered by passing through a celite pad, and the separated layer was dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure. The resultant residue was subjected to silica gel column chromatography (eluent; n-hexane: ethyl acetate=50:1) to afford the desired product, (RS)-2-methyl-4-methylidene-3-(2-propenyl)-1-tert-butyldimethylsilyloxycyclopent-2-ene (5.5 g, yield 88.4%) as a pale yellow oil.

1. temperaturethe resulting mixture was cooled to 0°~5° C
2. customto react for 4 days at 0°~5° C
3. customto react for 12 hours at the same temperature
4. additionwas slowly added
5. filtrationthe reaction mixture was filtered
6. dry with materialthe separated layer was dried over anhydrous sodium sulfate
7. customThe solvent was evaporated under reduced pressure