Carbon Dioxide Radical Anion by Photoinduced Equilibration between Formate Salts and [11C, 13C, 14C]CO2: Application to Carbon Isotope Radiolabeling.

The need for carbon-labeled radiotracers is increasingly higher in drug discovery and development (carbon-14, ß-, t1/2 = 5730 years) as well as in positron emission tomography (PET) for in vivo molecular imaging applications (carbon-11, ß+, t1/2 = 20.4 min). However, the structural diversity of radiotracers is still systematically driven by the narrow available labeled sources and methodologies. In this context, the emergence of carbon dioxide radical anion chemistry might set forth potential unexplored opportunities. Based on a dynamic isotopic equilibration between formate salts and [13C, 14C, 11C]CO2, C-labeled radical anion CO2•- could be accessed under extremely mild conditions within seconds. This methodology was successfully applied to hydrocarboxylation and dicarboxylation reactions in late-stage carbon isotope labeling of pharmaceutically relevant compounds. The relevance of the method in applied radiochemistry was showcased by the whole-body PET biodistribution profile of [11C]oxaprozin in mice.

Unlocking full and fast conversion in photocatalytic carbon dioxide reduction for applications in radio-carbonylation.

Harvesting sunlight to drive carbon dioxide (CO2) valorisation represents an ideal concept to support a sustainable and carbon-neutral economy. While the photochemical reduction of CO2 to carbon monoxide (CO) has emerged as a hot research topic, the full CO2-to-CO conversion remains an often-overlooked criterion that prevents a productive and direct valorisation of CO into high-value-added chemicals. Herein, we report a photocatalytic process that unlocks full and fast CO2-to-CO conversion (<10 min) and its straightforward valorisation into human health related field of radiochemistry with carbon isotopes. Guided by reaction-model-based kinetic simulations to rationalize reaction optimisations, this manifold opens new opportunities for the direct access to 11C- and 14C-labeled pharmaceuticals from their primary isotopic sources [11C]CO2 and [14C]CO2.

Carbon isotope labeling of carbamates by late-stage [11C], [13C] and [14C]carbon dioxide incorporation.

A general procedure for the late-stage [11C], [13C] and [14C]carbon isotope labeling of cyclic carbamates is reported. This protocol allows the incorporation of carbon dioxide, the primary source of carbon-14 and carbon-11 radioisotopes, in a direct, cost-effective and sustainable manner. A disconnection/reconnection strategy, involving ring opening/isotopic closure, was also implemented.