A Highly Efficient Synthesis of Z‐Macrocycles Using Stereoretentive, Ruthenium‐Based Metathesis Catalysts

A highly efficient, Z ‐selective ring‐closing metathesis system for the formation of macrocycles using a stereoretentive, ruthenium‐based catalyst supported by a dithiolate ligand is reported. The catalyst is remarkably active as observed in initiation experiments showing complete catalyst initiation at −20 °C within 10 minutes. Macrocyclization reactions generated Z ‐products from easily accessible diene starting materials bearing a Z ‐olefin moiety. This approach provides a more efficient and selective route to Z ‐macrocycles relative to previously reported systems. Reactions were completed within shorter reaction times, and turnover numbers of up to 100 could be achieved. Macrocyclic lactones ranging in size from twelve‐ to seventeen‐membered rings were synthesized in moderate to high yields (67–79 %) with excellent Z ‐selectivity (95–99 %).