High molar activity [11C]phosgene from [11C]CO2

[ 11 C]Phosgene is a known but underutilised labelling synthon in PET-tracer development. The production of [ 11 C]phosgene faces many problems such as difficulties in achieving high molar activity, regular key component replacement and complexity of the synthesis, thereby hindering its wider use. In this paper, a robust and semi-automated synthesis route for production of [ 11 C]phosgene from [ 11 C]CO 2 was developed to solve issues restricting the use of [ 11 C]phosgene. The high molar activity [ 11 C]phosgene was then used for the labelling of biologically important molecules as a proof of concept. [ 11 C]Phosgene was synthesized from [ 11 C]CO by UV-mediated photochemical chlorination with chlorine gas. [ 11 C]CO was produced by the fluoride-activated disilane reduction of cyclotron-produced [ 11 C]CO 2 . [ 11 C]Phosgene was produced with satisfactory radiochemical yield (13 ± 1 GBq at EOS, 30 ± 4% dc. to SOS) based on [ 11 C]CO 2 and molar activity of 249 ± 40 GBq/µmol at EOS (n = 3). The radiosynthesis time was approximately 20 min. A robust synthesis route for production of high molar activity [ 11 C]phosgene from [ 11 C]CO 2 was developed. The simplicity and mild reaction conditions of the [ 11 C]CO production method used eliminate the previous issues with Zn-based reduction of [ 11 C]CO 2 . Intermediate purification of [ 11 C]CO guaranteed efficient [ 11 C]phosgene production, and removal of unreacted Cl 2 minimised unwanted side reactions. This method utilises a fixed-line device with simple set up and mild conditions. With this method, it is possible to perform syntheses reliably with good radiochemical yields and high molar activities in a short synthesis time.