ortho -Functionalization of azobenzenes via hypervalent iodine reagents.

ortho -Functionalized azobenzenes are much sought after molecular switches, as they may be tuned to absorb in the visible range of light and the ( Z )-isomers can have high thermal half-lives. To enable straightforward access to these targets, we have developed a synthetic route via novel ortho -substituted azobenzene-functionalized diaryliodonium salts. Selective transfer of the azobenzene moiety to O-, N-, C- and S-nucleophiles under mild, transition metal-free conditions gives access to an unprecedented range of ortho -substituted azobenzenes. The photoswitching properties of the reagents were investigated and the structure was determined by X-ray crystallography.