The reagent prepared from a 2:1 molar ratio of the phosphine oxide and triflic anhydride is a useful dehydrating agent, e.g. for preparation of nitriles from amides or oximes, or of amides from acids and amines: J. Org. Chem., 52, 4137 (1987). In combination with triethylamine, the reagent also dehydrates activated ketones to alkynes: Synthesis, 217 (1989).