A copper-catalyzed procedure enabling dynamic carbon isotope exchange is described. Utilizing the universal precursor [ 14 C]CO 2 , this protocol allows to insert, in one single step, the desired carbon tag into carboxylic acids with no need of structural modifications. Reducing synthetic costs and limiting the generation of radioactive waste, this procedure will facilitate the access to carboxylic acids containing drugs and accelerate early 14 C-based ADME studies supporting drug development.

An integrated catalytic decarboxylation/carboxylation for accessing isotopically labeled carboxylic acids with 13CO2 or 14CO2 is described. The method shows a wide scope under mild conditions, even in the context of late-stage functionalization, and does not require stoichiometric organometallics, thus complementing existing carbon-labeling techniques en route to carboxylic acids.