Effects of Olefin Substitution on the Ring-Closing Metathesis of Dienes.

Ruthenium alkylidene 1 and molybdenum alkylidene 2 have been utilized in the ring-closing metathesis (RCM) of dienes containing gem-disubstituted olefins to yield tri- and tetrasubstituted cyclic olefins. Dienes with sterically demanding and/or electron-withdrawing substituents such as Ph, CO(2)Me, and (t)()Bu were cyclized successfully with 2, but did not cyclize with 1. Tetrasubstituted cyclic olefins could be formed with 2, but not using alkylidene 1. Dienes with allylic functional groups yielded functionalized cyclic olefins when treated with 1.