[ 11 C]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 11 C‐methylation with [ 11 C]CH 3 I/[ 11 C]CH 3 OTf, 11 C‐carbonylation with [ 11 C]CO, and 11 C‐carboxylation of organometallic reagents with [ 11 C]CO 2 , 11 C‐cyanation with [ 11 C]HCN is another frequently used 11 C‐labeling methodology. It can lead to the generation of [ 11 C]organo‐nitriles, [carbonyl‐ 11 C]carboxylic acids, [carbonyl‐ 11 C]aldehydes, [carbonyl‐ 11 C]amides, [ 11 C]alkyl amines, [tetrazoyl‐ 11 C]tetrazoles, [ 11 C]CN‐containing heterocycles, etc. This review recognizes the important roles of 11 C‐cyanation reactions with the emphasis of recent advances, along with the discussion of molar activities (A m ) of [ 11 C]HCN based radiotracers and prompts for future potential [ 11 C]cyanide based radiotracer development.