A Mild Method for Regioselective Labeling of Aromatics with Radioactive Iodine

A novel technique to label ortho-, meta-, and para-trimethylsilyl-substituted aryl substituents with radioactive iodide is described. The method takes advantage of the ipso-directing and activating properties of trimethylsilyl substituents on the arenes. The method was demonstrated on a griseofulvin analogue with promising anticancer properties and on lidocaine, a widely used local anesthetic drug. Treatment of a trimethylsilyl precursor with Tl(OCOCF3)3 followed by Na125I consistently afforded radioactive purities over 95% in all cases.