One-Two Punch For Diaryl Iodide Reagents

Diaryliodonium salts are becoming popular arylating reagents in organic synthesis because they are highly reactive crystalline solids that are easy to make and use. One strike against the compounds is that they have poor atom economy—that is, usually only one aryl group ends up being transferred to the substrate molecule, leaving an aryl iodide as waste. Sachin G. Modha and Michael F. Greaney of the University of Manchester, in England, wondered whether the extraneous aryl iodide could somehow be used in a second arylation reaction. Indeed, the researchers found after optimizing reaction conditions that they can carry out copper-catalyzed C–H arylation of indoles followed by N-arylation of the same indole molecule (shown) using the same copper catalyst and leftover aryl iodide (J. Am. Chem. Soc. 2015, DOI: 10.1021/ja5124754).