反应详情

To a cooled (0°-5° C.), magnetically stirred solution of 0.238 g (0.63 mmol) of the product of step A and 0.197 g (0.75 mmol) of triphenylphosphine dissolved in 3 mL of dichloromethane was added 0.287 g (0.75 mmol) of carbon tetrabromide in several portions. After the addition was complete, the reaction was allowed to warm to room temperature and was stirred 2.5 hours. At this point TLC analysis (50% EtOAc-hexane) indicated that starting material remained, therefore an additional 0.030 g of triphenylphosphine and 0.050 g of carbon tetrabromide were added. After 4 hours, the methylene chloride was removed in vacuo, and the residue was applied to a silica gel flash chromatography column and eluted with 10% EtOAc-hexane. Evaporation of the purified fractions and drying in vacuo afforded 0.271 g (96%) of the title compound.

1. additionAfter the addition
2. waitAfter 4 hours
3. customthe methylene chloride was removed in vacuo
4. washeluted with 10% EtOAc-hexane
5. customEvaporation of the purified fractions
6. customdrying in vacuo