Molybdenum‐Based Complexes with Two Aryloxides and a Pentafluoroimido Ligand: Catalysts for Efficient Z‐Selective Synthesis of a Macrocyclic Trisubstituted Alkene by Ring‐Closing Metathesis

Olefin metathesis catalysts for controlling the formation of trisubstituted macrocyclic Z alkenes have been developed. The most effective complexes are Mo alkylidenes with a pentafluorophenylimido group and two large aryloxide ligands. The macrocyclic lactone precursor to anticancer agents epothilones B and D is obtained in 73 % yield and 91 % Z selectivity in less than 6 hours at room temperature.