Synthesis of [ 14 C 6 ‐3,4,7,8,11,12]‐(1 E ,5 E ,9 E )‐cyclododeca‐1,5,9‐triene

Trimerization of butadiene in the presence of Ni(0) affords (1 E ,5 E ,9 E )‐cyclododeca‐1,5,9‐triene 1 ( ttt ‐CDT), (1 E ,5 E ,9 Z )‐cyclododeca‐1,5,9‐triene 2 ( ttc ‐CDT), and other isomers/oligomers. After optimization of reaction conditions, [ 14 C 6 ‐3,4,7,8,11,12]‐ ttt ‐CDT 1 was synthesized efficiently either by homogenous or heterogeneous Ni(0) catalytic trimerization of [1,4‐ 14 C 2 ]butadiene 10 , in 60–82% yield. Depending on the exact reaction conditions employed, the yields and ratio of 1 / 2 ranged from (59–90%) / (41–10%). The all‐ trans isomer was conveniently isolated via Ag + ‐mediated reversed‐phase HPLC. The important intermediate [1,4‐ 14 C 2 ]‐1,3‐butadiene 10 was prepared from potassium [ 14 C]cyanide and 1,2‐dibromoethane 3 as starting materials, in seven steps with a 57% yield. The total radioactive yield of [ 14 C 6 ‐3,4,7,8,11,12]‐ ttt ‐CDT 1 is 30% from [ 14 C]KCN. Copyright © 2007 John Wiley & Sons, Ltd.