Air- and water-stable Lewis acids: synthesis and reactivity of P-trifluoromethyl electrophilic phosphonium cations

A new class of electrophilic phosphonium cations (EPCs) containing a –CF₃ group attached to the phosphorus(V) center is readily accessible in high yields, via a scalable process. These species are stable to air, water, alcohol and strong Brønsted acid, even at raised temperatures. Thus, P–CF₃ EPCs are more robust than previously reported EPCs containing P–X moieties (X = F, Cl, OR), and despite their reduced Lewis acidity they function as Lewis acid catalysts without requiring anhydrous reaction conditions.