Abstract
We prepared a series of chiral 3,4-bisallyloxybut-1-ynes having syn and anti configurations. Treatment of these substrates with Grubbs catalyst Cl <sub>2</sub> (PCy <sub>3</sub> ) <sub>2</sub> Ru = CHPh (3 mol %) preferably gave chiral dioxabicyclo[4.4.0]-decane (yields > 55%) in addition to dioxabicyclo[5.3.0]-decane in minor proportions. On substitution of the 4-allyloxy group of these substrates with a 4-but-2-enyloxy group, the metathesis reactions produced only dioxabicyclo [5.3.0] decane in the presence of Grubbs ruthenium-imidazolidene carbene catalyst.