Improvement in Olefin Metathesis Using a New Generation of Ruthenium Catalyst Bearing an Imidazolylidene Ligand:  Synthesis of Heterocycles

A number of heterocycles have been prepared in very good yields using 1,3-dimesitylimidazol-2-ylidene ruthenium benzylidene 1. This catalyst displays increased activity for ring-closing metathesis of some hindered heterodienes which did not cyclize using the Grubbs catalyst 2. The scope of the olefin metathesis has been expanded.