DIRECT TRITIUM LABELING OF MULTIFUNCTIONAL COMPOUNDS USING ORGANOIRIDIUM CATALYSIS

The tritium exchange labeling of a variety of complex compounds is ach ieved in the presence of catalyst precursor [(cod)Ir(PPh(3))(2)]BF4 an d limited amounts of tritium gas. The regioselectivity of exchange is high and consistent with empirical rules previously observed. High spe cific activity levels are often achieved, usually with specific aryl C -H bonds. However, remarkably efficient exchange occurs in certain N-a lkyl groups. Studies of intermolecular inhibition of catalytic exchang e suggest reasons why larger amounts of complex are sometimes required to label complex molecules; nevertheless, significant amounts of labe l incorporation into substrates can be achieved even stal ting with sm all amounts of labeling gas.