able regions in RNA from mammalian and yeast cells, over 100 times more than had been found before. But surprisingly, most of those regions remain unfolded Schematic of an in the cells. BacRNA G-quadruplex teria have many (RG4) shows four fewer RG4-prone RNA strands (solid regions, but those lines with arrows) regions fold much that encapsulate more readily into three flat “GRG4s in bacteria. quartet” planes, The findings sugeach containing four gest that some bound guanines. mechanism in The quartets eukaryotic cells are stabilized by actively prevents potassium ions RG4 formation, (spheres). whereas bacteria have evolved to deplete RG4-forming sequences, the researchers say. The study “provides unprecedented insights into the nature of RG4 formation” in cells and could have medical implications, comments Stefania Millevoi of the Cancer Research Center of Toulouse, an expert on the role of RG4s in disease.—STU BORMAN
ENERGY STORAGE
Watching trouble unfold in a running battery By devising a method that provides a detailed view inside a lithium-ion battery while it is running, researchers have come up with a way to gather reconnaissance information about processes that could trigger disastrous battery failure. Under some charging conditions, lithium can accumulate on a battery’s anode, leading to uncontrolled growth of needlelike metal dendrites that can cause hazardous short circuiting. Lithium metal, an ideal anode material based on its exceptional charge-storage capacity, carries a high dendrite risk. So manufacturers use lower capacity carbon anodes, which are safer but not fully dendrite-proof. To study this poorly understood process, Andrew J. Ilott and Alexej Jerschow of New York University and coworkers developed Millimeter-sized “shadows” cast by dendrites an 1H magnetic resonance growing inside a charging Li-ion battery can imaging (MRI) method be imaged in real time and at high resolution and used it to watch denby a new MRI method. drites grow inside a Li-ion battery as it was being charged (Proc. Nat. Acad. Sci. USA 2016, DOI: 10.1073/ pnas.1607903113). Unlike an earlier 7Li MRI method developed by the team, which images dendrites directly, the new method measures “shadows” formed by the magnetic properties of the growing dendrites in the surrounding electrolyte solution. Because the shadows are roughly 20 times as large as the dendrites, the new method provides much improved spatial resolution. It also boosts the time resolution, owing to the relatively shorter scan times for 1H NMR.—MITCH JACOBY
PROCESS CHEMISTRY
CREDIT: ANDREW J. ILOTT/NYU (MRI DENDRITES); SCIENCE (RNA QUADTRUPLEX)
▸ Blue-light special on perfluoroalkylations Direct trifluoromethylation of aromatic rings is an important synthetic tool for chemists. Although an abundance of new methods that use less harsh reagents, have
improved product selectivity, and minimize waste have been reported during the past decade, cost-effective scalable processes have remained underdeveloped. Corey R. J.
O N+ O
CF3
N CO2CH3 R Protected pyrrole
F 3C
N CO2CH3 H Recrystallized product
Ru(bpy)3Cl2, pyridine N-oxide
O
O
F3C O CF3 Trifluoroacetic anhydride
Kilogram-scale flow reactor system = blue LED light
Stephenson and his coworkers at the University of Michigan in collaboration with process chemistry researchers at Eli Lilly & Co. may have found a solution. The team has designed a scaled up photochemical flow reactor that employs an inexpensive reagent combination under mild conditions to produce kilogram amounts of trifluoromethylated arenes and heteroarenes (Chem 2016, DOI: 10.1016/j.chempr.2016.08.002). The researchers use 4-phenylpyridine N-oxide as a redox trigger that is activated by a blue light-absorbing ruthenium bipyridine catalyst. This photoredox system decarboxylates trifluoroacetic anhydride to generate a trifluoromethyl radical that reacts with an arene or heteroarene. Stephenson and his colleagues are able to recrystallize the crude reaction products to high purity and they have extended the reaction scope to include perfluoroethyl and perfluoropropyl products.—STEVE RITTER SEPTEMBER 26, 2016 | CEN.ACS.ORG | C&EN
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