Chemists fracture rings to install fluorine

Abstract

To construct new bonds, as chemists are wont to do, they must first break bonds. But some bonds give way easier than others. Researchers can readily split carbon-carbon double bonds for further functionalization, yet they struggle to crack relatively inert, C–C single bonds. A new method developed by Richmond Sarpong and coworkers at the University of California, Berkeley, now cleaves C–C bonds in nitrogen-containing rings (Science 2018, DOI: 10.1126/science.aat6365). Using an excess of a silver salt and a common fluorinating reagent, the reaction (example shown) unfurls the ring to a linear alkyl chain with a fluorine atom at one end, a functional group coveted by chemists for its ability to modulate a molecule’s properties. In some cases, the method also introduces a formyl group on the nitrogen at the other end. The team proposes that the reaction proceeds through oxidation followed by radical ring opening. They successfully opened four-membered rings