Spotlights Cite This: J. Am. Chem. Soc. XXXX, XXX, XXX−XXX
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Spotlights on Recent JACS Publications
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AN EASY ROAD FROM ALKYNES TO AMIDINES Alkynesmolecules containing at least one carbon−carbon triple bondare important molecules. Because of their wide availability, they are attractive compounds to use as starting materials and to create more industrially useful functional groups. However, due to its strength, the carbon−carbon triple bond can be difficult to completely break. Most known reactions that convert alkynes into other molecules are to form heterocycles and carbocycles. However, reactions to create different functional groups, such as ketones, carboxylic esters and (thio)amides, olefins, and nitriles, are less well known. Those that do exist usually require activated alkynes or expensive (and sometimes toxic) NH2-transition-metal compounds. Now Xihe Bi and co-workers have found a new direct transformation of alkynes into amidines (DOI: 10.1021/ jacs.8b11039). This transformation uses a silver catalyst to interconvert two highly useful functional groups into each other by a one-pot, four-component reaction. The reaction can utilize a wide variety of aryl-, heteroaryl-, alkyl-, and alkenyl-substituted terminal alkynes and tolerates a range of other functional groups. This pathway involves several steps, which can be manipulated in a strictly sequential order, leading to high reaction efficiency. As amidines are important in medicinal chemistry research, this reaction shows an easy way to access this useful functional group. Leigh Krietsch Boerner, Ph.D.
The high activity of these nanocatalysts offers a cheap and efficient option for carbon fixation and paves the way for other inexpensive, green organic synthesis routes. Dalia Yablon, Ph.D.
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THIOESTER-CONTAINING POLYMERS THAT ARE BUILT TO BREAK DOWN Traditional polymers have static molecular architectures. While chemists have found enormous flexibility in designing polymer properties around this constraint, there is increasing demand for polymers that undergo physical or chemical modifications in response to environmental changes. Many of these stimuli-responsive polymers have been developed, but only a small subset experience a change in their chemical backbone upon environmental variation. While these materials have diverse applications, such as in the development of recyclable polymers and more complex architectures, their design and synthesis are challenging. Will R. Gutekunst and co-workers have overcome several of these challenges to identify a new approach for generating thioester-containing polymers that break down in response to specific environmental conditions (DOI: 10.1021/ jacs.8b12154). The team improved on the well-known strategy of radical ring-opening polymerization by identifying a new thiolactone monomer that incorporates labile thioester functional groups into the polymer backbone. The use of this new monomer avoids some of the undesired reactivity observed in previous radical ring-opening polymerizations. Additionally, the thiolactone monomer is compatible with a diverse array of acrylate monomers that are traditionally too active to copolymerize with more common cyclic monomers. The resulting copolymers are shown to be stimuli-responsive through degradation when exposed to hydrolytic conditions or treated with cysteine methyl ester. Elizabeth Meucci
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A NEW PATH FOR GREEN, EFFICIENT CONVERSION OF CO2 Carbon fixation is the process of converting inorganic carbon, such as the stable and abundant CO2 in the Earth’s atmosphere, into more useful organic products, such as carbonates, carbamates, and ureas. Now, Jie-Sheng Chen, Xin-Hao Li, and co-workers report a new method for chemical fixation of CO2 based on a metal−semiconductor nanocatalyst (DOI: 10.1021/jacs.8b08267). Their reaction results in highly efficient cycloaddition of CO2 to epoxides, producing the cyclic carbonates used in applications such as lithium batteries. The chemists couple electron-deficient copper nanoparticles to electron-rich nitrogen-doped carbon (NC) to create a bifunctional Lewis acid−base nanocatalyst. Previously, metal−organic frameworks (MOFs) and porous ionic polymers were developed as heterogeneous catalysts, with organic ligands acting as Lewis acids and bases. Thus, Lewis acid and base groups were proven to be important in facilitating CO2 fixation, but this approach was complex and expensive. The material described in this strategy is a Mott− Schottky catalyst, where the Lewis acid and base sites were promoted through optimization of the Schottky barriers at the Cu/NC junction. © XXXX American Chemical Society
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BLOCK PARTY: CREATING STRATIFIED MOFs WITH DOMAIN BUILDING BLOCKS Metal−organic frameworks (MOFs)compounds made of metal ions or cluster “nodes” connected by organic ligands have found use in applications such as catalysis and gas storage. Researchers have uncovered thousands of metal− ligand combinations, and these materials have gradually grown in complexity, shifting from MOFs composed of a single type of node and ligand to multivariate MOFs composed of several different types of metals and ligands. Nathaniel L. Rosi and co-workers continue this trend, reporting in a new study a way to create multivariate stratified MOFs with building blocks that constitute separate domains (DOI: 10.1021/jacs.8b13502).
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DOI: 10.1021/jacs.9b01300 J. Am. Chem. Soc. XXXX, XXX, XXX−XXX
Journal of the American Chemical Society
Spotlights
The researchers showcase this method by creating core− shell structures made of different layered UiO-67 MOFs. Creating a rich library of these compounds, they further show that individual strata in these materials can be selectively modified post-synthetically using metalation or linkerexchange reactions. They also illustrate the versatility of this method, crafting layers of strata around plasmonic nanoparticle centers. The authors suggest that MOFs made with many distinct functional domains could eventually perform integrated series of tasks or could serve as highly selective filters for capturing and concentrating target analytes at specific domains. Christen Brownlee
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DOI: 10.1021/jacs.9b01300 J. Am. Chem. Soc. XXXX, XXX, XXX−XXX
