A conjunctive diiodoheptaene for the synthesis of C2-symmetric carotenoids

(2E,4E,6E,8E,10E,12E,14E)-2,15-Diiodo-6,11-dimethylhexadeca-2,4,6,8,10,12,14-heptaene, prepared by homometathesis, has been used in palladium-catalyzed Suzuki and Stille cross-coupling reactions with the appropriate partners to construct the C-2-symmetric carotenoids beta,beta-carotene, lycopene, synechoxanthin and 4,4'-diapo-psi,psi-carotene-4,4'-dial.