The intramolecular cycloadditions of some mono (ally1oxy)-and bis (ally1oxy) perchlorocyclopentadienes have been carried out. Even in the case of trisubstituted olefins, this internal cycloaddition process occurs in good yield. The allyloxy compounds (10, 11, 15, and 16) were prepared by treating hexachlorocyclopentadiene (9) with the corresponding allylic alcohol in basic solution. In only one case could the intermediate allyloxy diene be ...