Copper-mediated reduction of 2-[18F]fluoroethyl azide to 2-[18F]fluoroethylamine†

18F-labelled fluoroalkylamines are attractive reagents for the preparation of positron emission tomography tracers containing amine, amide, and N-heterocyclic moieties. Herein, we report that 2-[18F]fluoroethylamine can be obtained from 2-[18F]fluoroethyl azide by reduction with elemental copper under acidic conditions. Azide to amine reduction was achieved in near quantitative analytical yields within 30 min by heating a solution of 2-[18F]fluoroethyl azide in the presence of copper wire and aqueous trifluoroacetic acid. Subsequent reaction of 2-[18F]fluoroethylamine with benzoyl chloride in the presence of triethylamine provided N-[18F]fluoroethyl benzamide in 63% decay-corrected radiochemical yield from 2-[18F]fluoroethyl azide. The utility of the Cu(0)/H+ azide reduction method was further exemplified by preparation of the potential GABAA tracer 9H-β-carboline N-2-[18F]fluoroethylamide, which was obtained in 46% decay-corrected radiochemical yield by reaction of 2-[18F]fluoroethylamine with the corresponding 9H-β-carboline pentafluorophenyl ester. Copyright © 2012 John Wiley & Sons, Ltd.