SYNTHESIS OF C-11 LABELED ALPHA,BETA-UNSATURATED NITRILES

The preparation of the synthetically useful alpha,beta-unsaturated 1-C-11-labelled precursors acrylonitrile 1 and cinnamonitrile 2 by a palladium catalysed substitution reaction with potassium [C-11]cyanide on the corresponding vinylic bromides, are presented. The substitution reactions were carried out in several solvents (acetonitrile, benzene, 1,2-dichlorobenzene, dimethylsulphoxide, tetrahydrofuran) in the presence of the cyclic polyether 18-crown-6. The highest decay corrected radiochemical yield (70-95% not isolated, based on the amount of [C-11]cyanide used) of 1 and 2 were obtained in acetonitrile, with a reaction time of 3-4 min. [1-C-11]Acrylonitrile was used without purification in a model reaction to synthesize 2-cyano[C-11]ethyldimethyl malonate from sodium hydride/dimethyl malonate.