Silicon compounds in carbon-11 radiochemistry: present use and future perspectives

Positron emission tomography (PET) is a powerful functional imaging technique that requires the use of positron emitting nuclides. Carbon-11 ( 11 C) radionuclide has several advantages related to the ubiquity of carbon atoms in biomolecules and the conservation of pharmacological properties of the molecule upon isotopic exchange of carbon-12 with carbon-11. However, due to the short half-life of 11 C (20.4 minutes) and the low scale with which it is produced by the cyclotron (sub-nanomolar concentrations), quick, robust and chemospecific radiolabelling strategies are required to minimise activity loss during incorporation of the 11 C nuclide into the final product. To address some of the constraints of working with 11 C, the use of silicon-based chemistry for 11 C-labelling was proposed as a rapid and effective route for radiopharmaceutical production due to the broad applicability and high efficiency showed in organic chemistry. In the past years several organic chemistry methodologies have been successfully applied to 11 C-chemistry. In this short review, we examine silicon-based 11 C-chemistry, with a particular emphasis on the radiotracers that have been successfully produced and potential improvements to further expand the applicability of silicon in radiochemistry. The use of silicon-based reagents and precursors for carbon-11 labelling has shown wide applicability and robustness with short reaction times using mild conditions. In this review, recent advances and future perspectives are examined.