Palladium-mediated conversion of para-aminoarylboronic esters into para-aminoaryl-11C-methanes

Cross-couplings are an alternative to conventional 11C-methylations which are generally employed in PET tracer synthesis. Therefore, we set out to develop a general procedure for the synthesis of para-11CH3 labeled aromatic amines from the corresponding para-aminoarylboronic esters in the presence of free amines. Aryl boronic esters containing primary, secondary, and tertiary amines were successfully converted into corresponding labeled methyl derivatives in sufficient radiochemical yield to apply this method for tracer development. This procedure was applied to the labeling of CIMBI-712, a promising candidate for the in vivo imaging of the 5-HT7 receptor in the CNS.