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

A method is presented for preparing 1‐¹¹C]ethyl iodide from ¹¹C]carbon monoxide. The method utilizes methyl iodide and ¹¹C]carbon monoxide in a palladium‐mediated carbonylation reaction to form a mixture of 1‐¹¹C]acetic acid and 1‐¹¹C]methyl acetate. The acetates are reduced to 1‐¹¹C]ethanol and subsequently converted to 1‐¹¹C]ethyl iodide. The synthesis time was 20 min and the decay‐corrected radiochemical yield of 1‐¹¹C]ethyl iodide was 55 ± 5%. The position of the label was confirmed by ¹³C‐labelling and ¹³C‐NMR analysis. 1‐¹¹C]Ethyl iodide was used in two model reactions, an O‐alkylation and an N‐alkylation. Starting with approximately 2.5 GBq of ¹¹C]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 ¹¹C]carbon monoxide. Starting with 10 GBq of ¹¹C]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.