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

Abstract

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 radio-chemical 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.