A ONE-STEP PREPARATION OF THE NCA F-18 LABELED SYNTHONS - 4-FLUOROBROMOBENZENE AND 4-FLUOROIODOBENZENE

4-[F-18]Fluorobromo- and [F-18]fluoroiodobenzene are interesting precursors for organometallic nucleophilic reagents. A one-step preparation of these synthons was achieved by n.c.a. nucleophilic exchange on the corresponding 4-bromo- and 4-iodophenyl-trimethylammonium salts. The leaving ability of the trimethylammonium group increases strongly with decreasing basicity of the counter anion with the sequence: tosylate < methyl sulphate < iodide < (perchlorate) < triflate. Systematic optimization leads to radiochemical yields of 50 +/- 5% and 80 +/- 5% using dimethyl acetamide as a solvent within 5 min.