Ruthenium-Catalyzed Reductive Coupling Reaction of Propargylic Alcohols via Hydroboration of Allenylidene Intermediates

A novel ruthenium-catalyzed reductive coupling
reaction of propargylic alcohols has been found to afford the
corresponding 1,5-hexadiynes in good yields with high stereoselectivity. This catalytic reaction may proceed via hydroboration of the initially produced ruthenium−allenylidene intermediates with pinacolborane as a key step, disclosing a new
reactivity of the allenylidene complexes.