Direct tritium labeling of multifunctional compounds using organoiridium catalysis

Abstract

The tritium exchange labeling of a variety of complex compounds is achieved in the presence of catalyst precursor [(cod)Ir(PPh3)2]BF4 and limited amounts of tritium gas. The regioselectivity of exchange is high and consistent with empirical rules previously observed. High specific activity levels are often achieved, usually with specific aryl C-H bonds. However, remarkably efficient exchange occurs in certain N-alkyl groups. Studies of intermolecular inhibition of catalytic exchange suggest reasons why larger amounts of complex are sometimes required to label complex molecules; nevertheless, significant amounts of label incorporation into substrates can be achieved even starting with small amounts of labeling gas. © 1997 John Wiley & Sons, Ltd.