Phosphine-Catalyzed Reaction of Cyanohydrins with Activated Alkynes

A new method for preparing alpha-cyanoacrylates and alpha-cyanoenones is described. The procedure uses a phosphine-catalyzed alpha-C addition of cyanide ion, generated in situ from cyanohydrins, to activated alkynes. All unexpected tandem reaction producing benzylidenecyclopentanones is also described.