[¹¹C]HCN Radiochemistry: Recent Progress and Future Perspectives

Positron emission tomography (PET) is a unique non-invasive imaging tool for studying in vivo biological processes. It utilizes short-lived positron emitter labeled organic molecules to study biological events in real-time. To incorporate the positron emitter into a molecule of biological interest, radioactive synthons are developed to facilitate radiolabeling chemistry. In addition to ¹¹C-methylation with [¹¹C]CH₃I/[¹¹C]CH₃OTf, ¹¹C-carbonylation with [¹¹C]CO, and ¹¹C-carboxylation of organometallic reagents with [¹¹C]CO₂, ¹¹C-cyanation with [¹¹C]HCN is another frequently used ¹¹C-labeling methodology. It can lead to the generation of [¹¹C]organo-nitriles, [carbonyl-¹¹C]carboxylic acids, [carbonyl-¹¹C]aldehydes, [carbonyl-¹¹C]amides, [¹¹C]alkyl amines, [tetrazoyl-¹¹C]tetrazoles, [¹¹C]CN-containing heterocycles, etc. This review recognizes the important roles of ¹¹C-cyanation reactions with the emphasis of recent advances, along with the discussion of molar activities (A_m) of [¹¹C]HCN based radiotracers and prompts for future potential [¹¹C]cyanide based radiotracer development.