An evaluation of a high‐pressure 11CO carbonylation apparatus

[¹¹C]Carbon monoxide (¹¹CO) is a versatile building block for the synthesis of Positron Emission Tomography (PET) radioligands. However, the difficulty of trapping ¹¹CO in a small solvent volume has limited its utility. We here report an evaluation of a simple, fully automated high‐pressure synthesizer prototype for the use in ¹¹C‐carbonylation reactions. [¹¹C]Carbon monoxide was easily prepared by online reduction of [¹¹C]carbon dioxide using either Mo(s) or Zn(s) as the reducing agent. The conversion yield of ¹¹CO was >99% when zinc was used as the reducing agent, and the corresponding value for Mo was approximately 71%. When the Zn or Mo column was constantly kept under inert atmosphere, no significant decrease in reducing properties was observed for more than 100 ¹¹CO productions. However, in our hands, Mo reductant was much easier to service. A total of nine functional groups were successfully radiolabeled using the ¹¹CO synthesizer prototype. All measured radiochemical yields exceeded 37%, and the ¹¹CO trapping efficiency was generally above 90%, except for the Suzuki coupling where the trapping efficiency was 80%. This high‐pressure synthesizer using [¹¹C]carbon monoxide as the labeling precursor is easy to operate allowing for ¹¹C‐carbonylation reactions to be performed in a high yield and in a routinely fashion.