Synthesis of substituted [C-11]ureas and [C-11]sulphonylureas by Rh(I)-mediated carbonylation

The urea moiety is present in many biologically active compounds and thus an attractive target for C-11-labelling. To extend the scope of the rhodium(I)-mediated carbonylative cross-coupling reaction between an azide and an amine and investigate its tolerance for functional groups, we have synthesized eight ureas and two sulphonylureas that were C-11-labelled in the carbonyl position. The decay-corrected analytical radiochemical yields were in the range of 14-96% (from [C-11] carbon monoxide). For example: starting from 1.33 GBq [C-11] carbon monoxide, 0.237 GBq (66%) of the cytotoxic sulphonylurea [C-11] LY-181984 11 was isolated within 60 min from end of bombardment. The mild reaction conditions and generality regarding functional groups of this method make it an attractive alternative to the [C-11] phosgene method for the synthesis of C-11-labelled ureas.