Effect of alkene structure on the course of reactions with XeF2 and CsSO4F

Abstract

XeF₂ reacted at room temperature in dichloromethane in the presence of HF with triphenylethene, 9-benzylidenefluorene and tetraphenylethene to form vicinal difluorides in high yield, the relative reactivities being in the following order: 1,1-diphenylethene:triphenylethene:tetraphenylethene : 9-benzylidenefluorene = 0.4 : 1 : 1.1 : 0.2. CsSO₄F did not react at 35 °C with phenyl substituted alkenes in dichloromethane, while vicinal fluoro-methoxy adducts were formed in the presence of methanol. The methoxy group entered according to the Markovnikov rule for regioselectivity in the case of triphenylethene and 9-benzylidenefluorene, with the relative reactivities: 1,1-diphenylethene:triphenylethene:tetraphenylethene:9-benzylidenefluorene = 1.2 : 1 : 0.2 : 0.3.