Synthesis of trisubstituted alkenes via olefin cross-metathesis.

[formula: see text] Trisubstituted alkenes have been prepared for the first time via intermolecular olefin cross-metathesis, using 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene ruthenium alkylidene complexes 3a,b in good yields with moderate E selectivity. In addition, protected alcohols near the geminal disubstituted olefin improve reactivity for cross-metathesis.