Synthesis of dienynes from alkenes and diynes using ruthenium-mediated ring-closing metathesis

This communication describes a novel ruthenium-mediated transformation, which converts molecules containing alkenes and conjugated diynes such as 1-allyl-2-{[6-(2-allylphenoxy)-2,4-hexadiynyl]oxy}benzene into dienynes such as 3-[2-(2,5-dihydro-1-benzoxepin-3-yl)-1-methylene-2-propenyl]-2,5-dihydro-1-benzoxepine instead of the expected product 3-[2-(2,5-dihydro-1-benzoxepin-3-yl)ethynyl]-2,5-dihydro-1-benzoxepine.