Abstract 3-Methanesulfonyloxypropyl tertiary amines were observed to cyclize to form azetidinium methanesulfonate moieties. Heat-induced cyclization of 3- methanesulfonyloxypropyl amines was utilized for preparation of azetidinium methanesulfonates. The azetidinium methanesulfonates were found to incorporate radioactive [18 F] fluoride (decay-corrected yields> 60%) efficiently, resulting in an efficient ...