Reductive amination of carboxylic acids and [C-11]magnesium halide carboxylates

The reductive amination of carboxylic acids was shown to be promoted by 2-chloropyridine hydrochloride (3 eq). It allowed the one-pot preparation of N-alkylamines in yields up to 93% from carboxylic acid (1 eq), amine (1 eq) and sodium borohydride (5 molar eq). The reaction, carried out with [C-11]magnesium halide carboxylates (C-11, beta(+), t(1/2):20 min), led to N-[C-11]alkylamines in 20-25% radiochemical yields (decay corrected to the end of bombardment, 30 min preparation time from [C-11]CO2). In this case, the addition of pyridinium salts led only to the corresponding [C-11]carboxylic acids.