Feasibility of palladium‐catalyzed isotopic exchange between sodium [¹²⁵I]I and 2‐iodo‐<i>para</i>‐carborane

Abstract

Abstract Many ortho‐/meta‐/para‐closo ‐carborane derivatives have been proposed for boron neutron capture therapy. However, it is difficult to follow their pharmacokinetics in patients, which creates a risk of suboptimal treatment. Adding a radioactive label to closo ‐carboranes may simplify pharmacokinetic studies. This paper reports on a study of the feasibility of palladium‐catalyzed isotopic exchange of iodinated closo‐ carborane with radioisotopes of iodine. 2‐iodo‐ para ‐carborane was selected as a model compound. It was shown that such isotopic exchange is possible and provides a high yield (83±4.2%) after 40 min of reaction time. The reaction conditions were optimized, and it was demonstrated that the presence of tetra n ‐butylammonium hydrogensulfate is important in order to stabilize the catalyst and to give reproducibility of the labeling. Copyright © 2003 John Wiley &amp; Sons, Ltd.