Table 3.

Synthesis of unsymmetrical [¹¹C]ureas by coupling anilines or aniline derivatives and aliphatic amines with [¹¹C]carbonyl difluoride.

^[a]L-Phenylalanine in H₂O-MeCN (1 : 1 v/v; 100 μL) with 1 equiv. of NaOH.

^[b]50 μmol 4-fluoroaniline was used, giving a 57 : 43 mix of [¹¹C]13 to [¹¹C]1,3-di-4- fluorophenyl urea.

^[c]50 μmol 1,2-diaminobenzene and 1 μmol pyridine were used.

^[d]HCl salt of hydrazine precursor in H₂O-MeCN (1 : 1 v/v; 100 μL) and 1 equiv. of KOH were used.

^[e]50 μmol arylamine precursor and 10 μmol pyridine were used. Yields are decay-corrected and based on radioactivity recovered from the HPLC purification of a reaction aliquot (n = 2). The synthesis time was 6.5 min from release of [¹¹C]carbon monoxide.