ies of the fruits. Interestingly, cucumber, melon, and watermelon plants continue to make the defensive compounds in other parts of the plant, such as roots, leaves, and stems, using other transcription factors: It’s a useful workaround to satisfy their human masters, while maintaining some armor.—SARAH EVERTS
TISSUE ENGINEERING
▸ Layered structure improves patch conductivity In tissue engineering applications, scaffolds made of conducting polymers can provide a pathway for communication between cells. But many such polymers quickly lose their conductivity under physiological conditions. Damia Mawad and Molly M. Stevens of Imperial College London and
CATALYSIS
Bismuth provides catalytic surprises A research team led by Berthold Hoge of Bielefeld University has gone into a little-used corner of the periodic table to develop a new set of highly active catalysts—bismuth perfluoroalkylphosphinates—that could be useful in industrial organic synthesis (Chem. Eur. J. 2016, DOI: 10.1002/ chem.201604914). Although bismuth is a rare heavy metal, and the heaviest stable element in the periodic table to boot, it’s F F F F relatively inexpensive as a by-product of copper, F F lead, and tin mining. And unlike most heavy P F F metals, its salts have remarkably low toxicity— F O F O most are less toxic than table salt. With those attributes, chemists are increasingly attracted Bi to bismuth salts as Lewis acid catalysts to replace corrosive and toxic industrial catalysts such as boron trifluoride. Some examples such O as bismuth triflate, Bi(SO3CF3)3, have already F F F F F F been successfully tested. But they are moisP F F ture sensitive. Hoge and his team found that F F switching to fluoroalkylphosphinates creates O air- and moisture-stable compounds without A bismuth(V) catalyst altering the Lewis acidity. To make bismuth(III) catalysts, the researchers treated commercially available Bi(C6H5)3 with perfluoroalkylphosphinic acid, (C2F5)2P(O)OH. To make an unprecedented bismuth(V) catalyst, they treated Bi(C6H5)3Cl2 with Ag[(C2F5)2PO2]. Hoge and his colleagues showed that these bismuth phosphinates are versatile in mediating a range of carbon-carbon bond-forming reactions, including Friedel-Crafts alkylation and the Diels-Alder reaction.—STEVE RITTER
to make the patches adhere to heart tissue in live rats for at least two weeks without sutures.—CELIA ARNAUD
CREDIT: DAMIA MAWAD
A new conducting polymer patch improves conduction of electrical signals across heart tissue. coworkers have devised a new way of improving the electronic stability of conducting polymers (Sci. Adv. 2016, DOI: 10.1126/ sciadv.1601007). The researchers make patches out of phytic acid-doped polyaniline on top of a chitosan film. The dopant converts the polyaniline from an insulating to a conducting state, but loss of the dopant limits the conductivity lifetime. For that reason, the team uses a chitosan layer under the polyaniline, which helps hold the phytic acid in place and keeps the patch in a conductive state even after two weeks in physiological buffer. The researchers tested the patches in explanted rat hearts, both thin slices and whole hearts, and showed that the conductive patch enhanced conduction of the electric signal across heart scar tissue. By adding a photoactive dye and using visible light, the team was able
SYNTHESIS
▸ Coupling phenols and allylic alcohols
The reaction, which is catalyzed by palladium in the presence of a chiral pyridine oxazoline ligand, creates building blocks that would be tough to make using more common synthetic reactions, such as a Michael addition (example shown). Sigman’s team selected allylic alcohols as the alkene in the reaction in order to influence which hydrogen would be removed during the β-elimination to form the chiral product. The chemists show the reaction works with a broad scope of allylic alcohols and phenols, and even successfully swaps the phenol for cumene hydroperoxide in several examples. Next, they plan to explore the scope of the reaction with other heteroatom nucleophiles that are compatible with the coupling strategy.—BETHANY
Although chemists have plenty of ways to add carbon atoms to alkenes—including the Nobel Prize-winning Heck reaction— they have fewer options when working with heteroatom nucleophiles, such as alcohols. Now, Matthew S. Sigman and his group at the University of Utah report an intermolecular oxa-Heck reaction that HALFORD allows them to couple phenols with allylic alcohols in an enantioselecPalladium catalyst, OH tive manner chiral ligand OH + (J. Am. Chem. Soc. 2016, Allylic alcohol DOI: 10.1021/ Phenol jacs.6b11486).
O
O H
Enantioselective coupling product
DECEMBER 5, 2016 | CEN.ACS.ORG | C&EN
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