Iododestannylation: an improved synthesis of [125I]iodoproxyfan, a specific radioligand of the histamine H3 receptor

[125I]Iodoproxyfan, a specific radioligand of histamine H3 receptors, was synthesized in 60% yield under very mild conditions from a tributylstannyl precursor. The arylstannane, which was obtained in a palladium-catalyzed reaction of arylbromide and hexabutylditin, smoothly underwent radioiodination with [125I]sodium iodide and chloramine-T to give tritylated [125I]iodoproxyfan. Final detritylation was achieved with formic acid 90% at room temperature. Compared to the original copper(I)-mediated halogen exchange this procedure has major advantages in terms of cost and ease of use.