Selective Access to Trisubstituted Macrocyclic E- and Z-Alkenes from the Ring-Closing Metathesis of Vinylsiloxanes

Macrocyclic (E)-alkenylsiloxanes, obtained from E-selective ring-closing metathesis reactions, can be converted to the corresponding (Z)-alkenyl bromides and (E)-alkenyl iodides allowing access to both E- and Z-trisubstituted macrocyclic alkenes. The reaction conditions and substrate scope of these stereoselective transformations are explored.