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

Abstract

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.

Enantioselective Main Group Catalysis: Modern Catalysts for Organic Transformations

“…Therefore, for the purpose of this review we have limited this to catalysis using the s-block elements and the p-block elements which are not typically considered as organocatalysts. There has been a resurgence in main group chemistry in the past decade, with many s-and p-block centered systems acting as efficient catalysts in a vast multitude of reactions such as cyclizations, hydrogenations and annulations amongst many others [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. Whilst many of these have been shown to be very effective, routinely obtaining quantitative conversions, any control of enantioselectivity has either been minimal or an incidental by-product.…”

Difluorotriorganylphosphoranes for the Synthesis of Fluorophosphonium and Bismuthonium Salts

“…Some of these species are effective catalysts in hydrodefluorination, hydrosilylation and hydrodeoxygenation processes , . The remarkable Lewis acidity of these fluorophosphonium compounds is most certainly caused by the presence of electron‐withdrawing perfluoroorganic substituents (here C 6 F 5 ) or cationic imidazolium and pyridinium groups.…”

Deoxygenative Fluorination of Phosphine Oxides: A General Route to Fluorinated Organophosphorus(V) Compounds and Beyond

“…Pyridine‐substituted compound 9 and furan‐substituted compound 10 were both formed in good yields, indicating both electron‐rich and electron‐deficient heteroaromatic substituents are compatible (Figure 1). (Note that compound 9 is a precursor to an established phosphonium ion catalyst used for Friedel–Crafts dimerization, hydrodefluorination, and hydrodeoxygenation, among other reactions) [22] . Additionally, we found that alkyl substituents stay intact during deoxygenative fluorination (compound 11 ).…”