Iodonium ylides for one-step, no-carrier-added radiofluorination of electron rich arenes, exemplified with 4-(([18F]fluorophenoxy)-phenylmethyl)piperidine NET and SERT ligands
Iodonium ylide precursors of electron rich arenes, i.e. the NET and SERT ligands 4-((3- and 4-fluorophenoxy)phenylmethyl)piperidine, served as model compounds for the direct substitution with n.c.a. [18F]fluoride. Good radiochemical yields of about 20% were obtained in reaction times of ca. 130 minutes with a molar activity of the labelled ligands of more than 50 GBq μmol−1. Those failed as in vivo probes in first evaluation studies. Several important insights, however, were gained into the reaction of ylides, e.g. an unexpected formation of regioisomers. The results clearly demonstrate that aryliodonium ylides are a promising alternative to the well-known diaryliodonium salts for the direct preparation of complex, electron rich n.c.a. [18F]fluoroarenes.