The Role of an Acid in the Decomposition of Mixed Benzoyl-Substituted Phosphonium–Iodonium Ylide

Abstract—Mixed phosphonium–iodonium ylides allow the synthesis of not easily accessible and novel heterocyclic compounds. Photoinitiated reactions of phosphonium–iodonium ylides with acetylenes proceed with induction time and are catalyzed by acids, the acids formed in the reaction among them. The kinetic peculiarities of the reaction between the benzoyl-substituted phosphonium–iodonium ylide and trifluoroacetic acid were studied by UV-visible spectrophotometry. The kinetic parameters of the reaction were determined. The mechanism of the autocatalysis by acids has been proposed, which involves the formation of a protonated form of the ylide active in the decomposition into radical cations. The more active decomposition of the protonated ylide is confirmed by theoretical thermochemical calculations.