Synthesis of [1‐ 11 C]ethyl iodide from [ 11 C]carbon monoxide and its application in alkylation reactions

A method is presented for preparing [1‐ 11 C]ethyl iodide from [ 11 C]carbon monoxide. The method utilizes methyl iodide and [ 11 C]carbon monoxide in a palladium‐mediated carbonylation reaction to form a mixture of [1‐ 11 C]acetic acid and [1‐ 11 C]methyl acetate. The acetates are reduced to [1‐ 11 C]ethanol and subsequently converted to [1‐ 11 C]ethyl iodide. The synthesis time was 20 min and the decay‐corrected radiochemical yield of [1‐ 11 C]ethyl iodide was 55 ± 5%. The position of the label was confirmed by 13 C‐labelling and 13 C‐NMR analysis. [1‐ 11 C]Ethyl iodide was used in two model reactions, an O ‐alkylation and an N ‐alkylation. Starting with approximately 2.5 GBq of [ 11 C]carbon monoxide, the isolated decay‐corrected radiochemical yields for the ester and the amine derivatives were 45 ± 0.5% and 25 ± 2%, respectively, based on [ 11 C]carbon monoxide. Starting with 10 GBq of [ 11 C]carbon monoxide, 0.55 GBq of the labelled ester was isolated within 40 min with a specific radioactivity of 36 GBq/µmol. Copyright © 2004 John Wiley & Sons, Ltd.