New metathesis catalyst bearing chromanyl moieties at the N-heterocyclic carbene ligand

The synthesis of a new type of Hoveyda-Grubbs 2nd generation catalyst bearing a modified N-heterocyclic carbene ligands is reported. The new catalyst contains an NHC ligand symmetrically substituted with chromanyl moieties. The complex was tested in model CM and RCM reactions. It showed very high activity in CM reactions with electron-deficient alpha,beta-unsaturated compounds even at 0 degrees C. It was also examined in more demanding systems such as conjugated dienes and polyenes. The catalyst is stable, storable and easy to purify.