Supercharged bleach powers greener oxidations - C&EN Global

Run-of-the-mill liquid bleach, aqueous NaOCl, is an attractive green option for industrial oxidations. It's cheap and doesn't explode, and its waste p...
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▸ Supercharged bleach powers greener oxidations Run-of-the-mill liquid bleach, aqueous NaOCl, is an attractive green option for industrial oxidations. It’s cheap and doesn’t explode, and its waste product is table salt. But it is tough to work with and inefficient at large scale. Now researchers have determined that a crystallized bleach, sodium hypochlorite pentahydrate, oxidizes organic species more efficiently, often with higher yield and selectivity, than dilute household bleach (Org. Process Res. Dev. 2017, DOI: 10.1021/acs.oprd.7b00288). A few years ago, researchers at Nippon Light Metal (NLM) figured out a way to manufacture a stable, crystalline form—NaOCl•5H2O. In new research, Yoshikazu Kimura of Iharanikkei Chemical Industry, Masayuki Kirihara of Shizuoka Institute of Science & Technology, and coworkers, including at NLM, explored using the compound in a variety of industrial oxidations. The crystal is “a superior substitute” to aqueous bleach, Kimura says. The catalyzed oxidation of bulky secondary alcohols to ketones is “an especially remarkable example,” he adds. When catalyzed by tetrabutylammonium hydrogen sulfate and a nitroxyl-radical-based catalyst known as TEMPO, oxidation of 2-octanol to 2-octanone with liquid bleach generated the ketone in 11% yield after 22 hours. But with the crystalline form, the yield was 97% after just one hour. The compound also mediated some reactions that don’t work at all with aqueous bleach, such as oxidative cleavage of trans diols to diketones.—LOUISA DALTON, spe-

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▸ Designer peptides treat stomach pathogen About half the world’s population harbors Helicobacter pylori bacteria, which cause ulcers and cancer. Treatment of symptomatic patients usually involves triple therapy—two antibiotics and an acid reducer—but H. pylori resists some antibiotics. Treatment is also challenging because the pathogens reside in the stomach, where drugs need to tolerate

Chemists construct a symmetrical nortricyclene Apart from the grunt work and smells that come with being a chemist, there’s the artistry and an appreciation of the synthetic achievements in which elements are coupled together in beautiful or unexpected ways. In a recent example, a team led by Volodymyr Kozel and Günter OH Haufe of the University of Münster have synthesized a tricyclic triol that represents the smallest known HO molecule to display threefold symmetry in a chiral C3 axis polycyclic compound (Angew. Chem. Int. Ed. 2017, OH DOI: 10.1002/anie.201709279). Controlling the symmetry of molecules is often important for developThe new tricyclic ing pharmaceuticals and self-assembled macromotriol, labeled with its lecular materials. But designing for symmetry isn’t C3-symmetry axis. easy: Molecules with a twofold plane of symmetry are well established, and threefold symmetry is common for molecules like trisubstituted benzenes and triazines. But refining synthetic approaches to achieve threefold symmetry found in more structurally diverse molecules is still a work in progress. Haufe’s group has added to prior work on symmetric tricyclic molecules by designing a synthetic approach to functionalize a bicyclic alkoxy-substituted norbornadiene, which leads to a racemic mixture of the previously unknown C3-symmetric nortricyclene-3,5,7-triol (shown). With an enantiomeric resolution procedure, the team obtained pure enantiomers of the nortricyclene on a gram scale. In a collaboration with Merck KGaA researchers, the Münster team is using the new molecule to prepare dopants for liquid crystals with potential applications in integrated circuits.—STEVE RITTER

high acidity. JiStomach pH Normal physiological pH anjun Cheng and – O HO O O Lin-Feng Chen at the University of Illinois, UrbaH O H O N ( ( ) ) na-Champaign; )( )( N N N 20 20 20 20 H H Lichen Yin of O O – OH Soochow UniversiH+ ty; and coworkers O O O O have now devel( )4 ( )4 oped peptides that C H + C6H13 + 6 13 not only tolerate N N CH3 CH3 acidity but use it C6H13 C6H13 to activate their antibacterial activity (Proc. Natl. Under acidic conditions in the stomach, the new peptides, like Acad. Sci. USA the one shown, adopt a helical conformation (left) that kills 2017, DOI: 10.1073/ bacteria like H. pylori. At normal physiological pH, they adopt a pnas.1710408114). low-toxicity, random-coil conformation (right). Green balls are At low pH, such cationic amine groups, blue balls are anionic carboxylates, and as in the stomach, black balls are neutral (protonated) carboxyl groups. the orally administively, so they don’t kill “good” intestinal tered peptides adopt a positively charged helical conformation that kills bacteria by bacteria or hurt body cells. Liangfang Zhang of the University of California, San disrupting their membranes. At the normal physiological pH of the intestines and Diego, comments that in infected mice, the peptides have “impressive anti-H. bloodstream, the peptides transform into pylori efficacy, equivalent to that of triple a random-coil conformation that doesn’t therapy.”—STU BORMAN bind anything in particular very effecNOVEMBER 20, 2017 | CEN.ACS.ORG | C&EN

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