[11C]/(13C)Carbon monoxide in palladium-mediated synthesis of imides

[C-11]Carbon monoxide in low concentration with palladium(0) complexes (in the range of 5 mu mol) and aryl halides (about 10 mu mol) were used in the synthesis of the C-11-labelled imides, thalidomide, N-phthaloyl-L-glutamic acid, N-phthaloylhexane and aniracetam. The labellings were performed with ring closure reactions except in the case of aniracetam. These imides were obtained in nearly quantitative radiochemical yields, calculated from the [C-11]carbon monoxide, with specific radioactivities between 70-600 GBq mu mol(-1). The radiochemical purity of the LC-purified products exceeded 98%. N-(C-13)Phthaloyl-L-glutamic acid 2 was produced to verify the position of the label (delta 167.5 ppm) with C-13 NMR, and this also indicates that the discussed approach is valuable forlabelling with other carbon isotopes. In a typical experiment starting with 2.8 GBq of [C-11]carbon monoxide, 0.6 GBq of HPLC-purified [C-11]-N-phthaloyl-L-glutamic acid 2 was obtained within 40 minutes from the start of the carbonylation reaction (84% decay-corrected radiochemical yield).