Pyridinium-phosphonium dications: highly electrophilic phosphorus-based Lewis acid catalysts

摘要

Using commercially available 2-pyridyldiphenylphosphine (o-NC5H4)PPh2, a family of electrophilic phosphonium cations (o-NC5H4)PFPh2(+) (2) and dications (o-MeNC5H4)PRPh2(2+) (R = F (4); Me (5)) were prepared. The Lewis acidity of these pyridinium-phosphonium dications was probed in Friedel-Crafts dimerization, hydrodefluorination, hydrosilylation, dehydrocoupling and hydrodeoxygenation reactions. The influence of the counterion on the catalytic activity of the electrophilic phosphonium cations is also discussed.