Preparation of Macrocyclic <i>Z</i>‑Enoates and (<i>E</i>,<i>Z</i>)- or (<i>Z</i>,<i>E</i>)‑Dienoates through Catalytic Stereoselective Ring-Closing Metathesis

The first examples of c​atalyst-controlled stereo­selective macrocyclic ring-closing metathesis reactions that generate <i>Z</i>-enoates as well as (<i>E</i>,<i>Z</i>)- or (<i>Z</i>,<i>E</i>)-dienoates are disclosed. Reactions promoted by 3.0–10 mol % of a Mo-based mono­aryl­oxide pyrrolide complex proceed to completion within 2–6 h at room temperature. The desired macrocycles are formed in 79:21 to >98:2 <i>Z</i>/<i>E</i> selectivity; stereo­isomerically pure products can be obtained in 43–75% yield after chromatography. Utility is demonstrated by application to a concise formal synthesis of the natural product (+)-aspicilin.