Preparation of No-carrier-added [1- 11C]Ethylene and [1- 11C]1,2-Dibromoethane as new labelling agents

Abstract

A method is described for the preparation of NCA [1- 11C]ethylene based on the passage of [1- 11C]ethanol over heated (500°C) quartz glass in a stainless steel tube (in preference to dehydration by catalysis on γ-alumina or pyrolysis). The [1- 11C]ethanol is prepared from cyclotron-produced NCA [ 11C]carbon dioxide by 11C-carboxylation of methylmagnesium bromide, freshly prepared in dibutyl ether, and reduction of the adduct with lithium aluminium hydride in diglyme. The use of involatile solvents avoids the formation of carrier ethylene and radioactive and stable diethyl ether by cracking processes over the heated catalyst. The preparation takes 21 min from the end of radionuclide production and has a radiochemical yield of 44%, decay-corrected from [ 11C]carbon dioxide. NCA [1- 11C]ethylene is converted quantitatively into [1- 11C]1,2-dibromoethane when collected in a solution of bromine in carbon tetrachloride. The NCA [1- 11C]ethylene and [1- 11C]1,2-dibromoethane may serve as new and useful labelling agents.