A novel ruthenium-catalyzed carbon-carbon bond formation between propargylic alcohols and alkenes via the allenylidene-ene reaction has been found to afford the corresponding 2,4-disubstituted-1-hexen-5-ynes in moderate yields. The finding described here discloses a new reactivity of allenylidene complexes. As a synthetic application, intramolecular cyclization of propargylic alcohols bearing an alkene moiety has been developed to give the corresponding syn-substituted chromanes in high yields with an excellent diastereoselectivity.