Synthesis of a novel ¹²³I‐labelled derivative of GBR12783, a potential agent for SPECT imaging of dopamine‐reuptake sites

[¹²³I]1‐[2‐(Diphenylmethoxy)ethyl]‐4‐[3‐(m‐iodophenyl)‐2‐propenyl]piperazine ([¹²³I]2), a potential SPECT imaging agent for dopamine reuptake sites was efficiently synthesized in 4 steps from 1‐[2‐(diphenylmethoxy)ethyl]piperazine (3). A key step in the synthesis was the selective AIH₃‐mediated reduction of 1[2‐(diphenylmethoxy)ethyl‐4‐(m‐bromocinnamoyl] piperazine (4) to 1‐[2‐(diphenylmethoxy)ethyl‐4‐(3‐(m‐bromophenyl)‐2‐propenyl]piperazine(5). The ¹²³I label of [¹²³I]2 was introduced in the final step in up to 90% radiochemical yield by treatment of the organotin precursor 1‐(2‐(diphenylmethoxy)ethyl‐4‐[3‐[(m‐(tributyl stannyl)phenyl]‐2‐propenyl]piperazine (6) with Na¹²³I in aqueous CH₃CO₃H.