Synthesis of 13N-labelled polysubstituted triazoles: Via Huisgen cycloaddition

The use of the positron emitter nitrogen-13 (13N) has been historically restricted due to its short half-life (T1/2 = 9.97 min). However, its stable isotopes (nitrogen-14 and nitrogen-15) are present in many biologically active molecules; therefore, the incorporation of 13N in the toolbox of PET chemists might be a valuable option for the preparation of new labelled compounds or incorporation of the label in different positions. Here we present the unprecedented radiosynthesis of 13N-labelled polysubstituted triazoles via Huisgen cycloaddition by reaction of 13N-labelled aromatic azides with alkyne derivatives and aldehydes. Six different 13N-labelled triazoles were successfully synthesized. After automatization of the synthetic process and optimization of experimental conditions, one selected triazole could be prepared with high radiochemical purity and decay-corrected radiochemical yields of 11