A study on the enyne metathesis reaction leading to the formation cyclic compounds using ruthenium-indenylidene complexes is presented. Several 1,11-dien-6-ynes have been subjected to ruthenium metathesis cyclization by using ruthenium-indenylidene complexes bearing various phosphine and N-heterocyclic carbene (NHC) ligands. Interestingly, for some substrates chemodivergent metathesis occurs and is a function of the catalyst employed. This led us to investigate the competing ene-then-yne or yne-then-ene reaction pathways apparently at play in these systems using both experimental observations and DFT calculations. Experimental and computational studies were found in good agreement and permit to conclude that for phosphine-containing catalysts, the ene-then-yne pathway is exclusively adopted. On the other hand, for catalysts bearing NHC ligands, both pathways are possible.
Chemodivergent metathesis of dienynes catalyzed by ruthenium–indenyl complexes: An experimental and computational study
Chem. Eur. J. 2009, 15, 10244-10254.