Tritium‐labelling via an iridium‐based solid‐phase catalyst

A solid‐phase, iridium‐based ortho ‐exchange catalyst has been developed, with the aim of producing cleaner, more efficient, systems for tritium and deuterium labelling. The catalyst, which is a solvated polystyrene‐bound triphenylphosphine complex of cyclooctadienyliridium(I) hexafluorophosphate, was evaluated with respect to more conventional catalysts such as CODIr(PPh 3 ) 2 PF 6 and the Crabtree catalyst using simple model compounds as substrates. Labelling of drug candidate molecules proceeds with high regioselectivity and, after a simple filtration step, affords products with high radiochemical purities directly from the exchange reaction. The solid‐phase catalyst functioned well with a variety of traditional directing groups including nitro, amide, benzophenone and N ‐heterocycles. Copyright © 2007 John Wiley & Sons, Ltd.