Synthesis of diethyl [carbonyl-11C]malonate from [11C]carbon monoxide by rhodium-promoted carbonylation and its application as a reaction intermediate

✍ Scribed by Julien Barletta; Farhad Karimi; Hisashi Doi; Bengt Långström

• Publisher: John Wiley and Sons
• Year: 2006
• Tongue: French
• Weight: 134 KB
• Volume: 49
• Category: Article
• ISSN: 0022-2135
• DOI: 10.1002/jlcr.1098

✦ Synopsis

Rhodium-mediated carbonylation reaction was applied to synthesize diethyl [carbonyl-11 C]malonate using [ 11 C]carbon monoxide at low concentration. The synthesis was performed starting with ethyl diazoacetate, ethanol and the rhodium complex being made in situ by chloro(1,5-cyclooctadiene)rhodium(I) dimer ([Rh(cod)Cl] 2 ) and 1,2-bis(diphenylphosphino)ethane (dppe), and the reaction is assumed to proceed via a ketene intermediate. The isolated radiochemical yield was 20% (75% analytical radiochemical yield) and the trapping efficiency of [ 11 C]carbon monoxide in the order of 85%. The specific radioactivity of this compound was measured at 127 GBq/mmol (7.28 nmol total mass) after 8 mAh bombardment and 35 min synthesis. The corresponding 13 C-labelled compound was synthesized using ( 13 C)carbon monoxide to confirm the position of the carbonyl-labelled atom by 13 C-NMR. Diethyl [carbonyl-11 C]malonate was further used in subsequent alkylation step using ethyl iodide and tetrabutylammonium fluoride to obtain diethyl diethyl [carbonyl-11 C]malonate in 50% analytical radiochemical yield.