Improvement in olefin metathesis using a new generation of ruthenium catalyst bearing an imidazolylidene ligand: Synthesis of heterocycles

[GRAPHICS] A number of heterocycles have been prepared in very good yields using 1,3-d imesitylimidazol-2-ylidene ruthenium benzylidene 1. This catalyst displays increased activity for ring closing metathesis of some hindered heterodiene s which did not cyclize using the Grubbs catalyst 2. The scope of the olefi n metathesis has been expanded.