The syntheses of the acyclic dienynes 14 a (cis-trans-acetylene) and 14 b (trans-trans- acetylene) are described. The tandem macrocyclization and transannular Diels-Alder reaction of the allylic chloride 14 b was conducted in the presence of Cs2CO3 at 85° C in one-pot to provide tricyclic product 16, with the two hydrogens in ring B being cis. On the other hand, treatment of the allylic chloride 14 a under the same conditions afforded 14- ...