Synthesis of [14C6‐3,4,7,8,11,12]‐(1E,5E,9E)‐cyclododeca‐1,5,9‐triene

Trimerization of butadiene in the presence of Ni(0) affords (1E,5E,9E)-cyclododeca-1,5,9-triene 1 (ttt-CDT), (1E,5E,9Z)-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.