Synthesis of geminal enediynes with saturated and unsaturated carbocyclic backbones by palladium-catalyzed alkynylation of dibromoolefins

The conversion of cyclic diketones 1 and 3 into the corresponding dibromoalkenes 2 and 4 via Corey-Fuchs procedure is described. Subsequent alkynylation of 2 and 4 as well as 9-(dibromomethylene)fluorene (6) yields the geminal enediynes 5a-e, 7a-e, and 8a-c. The cyclohexane backbone of 5a,d can be oxidized with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to the p-quinoid systems 9a,b.