Keggin structure heteropolyacid-catalyzed phosphinylation of secondary propargyl alcohols with phosphine oxides to γ-ketophosphine oxides

O, indicating the participation of water in the reaction. Besides, our work underscores the importance and effect of a small amount of water, acting to promote the transformation of secondary propargyl alcohols into enones, which should be the real intermediates of the reaction. A mechanism involving a carbocation, Meyer-Schuster rearrangement and Michael addition of enones was proposed.