Stereoselectivity of macrocyclic ring-closing olefin metathesis

[GRAPHICS] Macrocyclic ring closing olefin metathesis using ruthenium catalyst 3 was p erformed to produce a 14-membered lactone. The E/Z ratio of lactone was hig h regardless of the R group (auxiliary) or the initial alkene stereochemist ry. A kinetic study demonstrates that the high E/Z ratio is due to secondar y metathesis reactions that isomerize the product to the thermodynamic E/Z ratio.