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

Abstract

The first examples of catalyst-controlled stereoselective macrocyclic ring-closing metathesis reactions that generate Z-enoates as well as (E,Z)- or (Z,E)-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 Z/E 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.