A convenient synthesis of ¹³N-labelled azo compounds: A new route for the preparation of amyloid imaging PET probes

In the present paper, a fast and automated method for the synthesis of ¹³N-labelled azo compounds is reported for the first time. The labelling strategy is based on trapping [¹³N]NO₂ ^- in an anion exchange resin. The reaction with primary aromatic amines in acidic media led to the formation of the corresponding diazonium salts, which were further reacted with aromatic amines and alcohols to yield the corresponding ¹³N-labelled azo derivatives with good radiochemical conversion (40.0-58.3%). Good radiochemical yields (20.4-47.2%, decay corrected) and radiochemical purities (>99.9%) were obtained after purification by HPLC. Such methodology can be easily applied to the preparation of a wide range of ¹³N-labelled azo derivatives by adequate selection of the non-radioactive precursors.