“On water”-promoted direct alkynylation of isatins catalyzed by NHC–silver complexes for the efficient synthesis of 3-hydroxy-3-ethynylindolin-2-ones

The direct alkynylation of isatins catalyzed by NHC–Ag complexes via the activation of alkyne C–H bond on water was developed for the efficient synthesis of 3-hydroxy-3-ethynylindolin-2-ones under an air atmosphere. A remarkable rate-enhancement by water in the aqueous heterogeneous system was observed.