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

Abstract

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 [¹¹C]magnesium halide carboxylates (¹¹C, β⁺, t_1/2∶20 min), led to N-[¹¹C]alkylamines in 20–25% radiochemical yields (decay corrected to the end of bombardment, 30 min preparation time from [¹¹C]CO₂). In this case, the addition of pyridinium salts led only to the corresponding [¹¹C]carboxylic acids.