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 and larger ones, but five-membered rings were mostly just oxygenated. The researchers also demonstrated the ring-opening fluorination of two peptides, a strategy that could be immediately applicable in drug discovery or biological uses, Sarpong says. In addition, the team showed the geminal difluorination of rings using 0.25 equivalents of a silver salt and hope to lower the amount of metal needed in future reactions.