反应详情

To 20 g of the compound of Example 20B suspended in 60 ml dichloromethane was added at -20° C. a solution of 100 ml trifluoroacetic acid anhydride in 40 ml dichloromethane. While stirring, an orange colored solution was obtained after 30 minutes. The solution was then stirred at 0° C. for one hour. The color turned to a dark green. The solvent, excess trifluoroacetic acidanhydride and formed trifluoroacetic acid was then distilled of in vacuo at room temperature. After evaporation with an oil-vacuo for additional one hour a beige foam was obtained. This was stirred with 150 ml ether and cooled to -20° C. A dark red suspension was obtained. After filtration and washing with ether and hexane the title compound was obtained as a beige solid (20.4 g). The compound is unstable and must be immediately used for further transformation.

1. customan orange colored solution was obtained after 30 minutes
2. stirringThe solution was then stirred at 0° C. for one hour