Cu-Catalyzed Cyanation of Arylboronic Acids with Acetonitrile: A Dual Role of TEMPO

The cyanation of arylboronic acids by using acetonitrile as the CN source has been achieved under a Cu(cat.)/TEMPO system (TEMPO=2,2,6,6-tetramethylpiperidine N-oxide). The broad substrate scope includes a variety of electron-rich and electron-poor arylboronic acids, which react well to give the cyanated products in high to excellent yields. Mechanistic studies reveal that TEMPOCH2CN, generated in situ, is an active cyanating reagent, and shows high reactivity for the formation of the CN- moiety. Moreover, TEMPO acts as a cheap oxidant to enable the reaction to be catalytic in copper.