New Concepts in Designing Ruthenium-Based Second Generation Olefin Metathesis Catalysts and Their Application

摘要

Strong enhancement of metathesis reactions using "second-generation" Ru-carbene complexes bearing N-aromatic groups was observed by switching from non-aromatic to aromatic solvents. Fluorinated aromatic solvents as reaction media enabled the completion of very challenging metathesis transformations, such as the formation of tetra-substituted olefins utilizing standard commercially available ruthenium catalysts. Further improvements in activity of the ruthenium carbene complexes ere achieved by incorporation of methyl groups in 3,4-position of imidazol-2-ylidene moiety. Introduction of sulfur in the trans-position to the N-heterocyclic carbene leads to increased stability of the resulting ruthenium complexes. The synthesis and the first applications of these new ruthenium complexes are described herein.