Palladium-mediated carboxylation of aryl halides (triflates) or benzyl halides using [13C]/[11C]carbon monoxide with tetrabutylammonium hydroxide or trimethylphenylammonium hydroxide

Abstract

[Carbonyl-¹¹C]carboxylic acids were synthesised using palladium-mediated reaction of [¹¹C]carbon monoxide with aryl halides/triflates and benzyl halides in combination with either tetrabutylammonium hydroxide or trimethylphenylammonium hydroxide. The radiochemical yields were in the range 20-85%. In a typical experiment starting with 2.1 GBq [¹¹C]carbon monoxide, 0.6 GBq of HPLC-purified 1-[carbonyl-¹¹C]naphthoic acid (13) was obtained within 25 min of the start of the carbonylation reaction (67% decay-corrected radiochemical yield). The specific radioactivity of [carbonyl-¹¹C]nicotinic acid (17) was in the order of 750 GBq µmol⁻¹ using 10.0 µAh bombardment. [Carbonyl-¹³C]nicotinic acid (17) was synthesised to verify the position of the labelling (δ 166.1) determined by ¹³C NMR.