Advances in the transition-metal-free cyclobutanol ring expansion to 4-tetralones under -bromosuccinimide mediation are described. We have expanded the scope of this ring expansion methodology and investigated the effect substituents on the aromatic ring, and the cyclobutanol moiety, have on the outcome of the reaction. Limitations with certain substituents on the cyclobutanol moiety are also described. Further experimental evidence to support our mechanistic understanding is disclosed, and we now preclude the suggested involvement of a primary radical for this transformation.
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http://dx.doi.org/10.1021/acs.joc.9b01290 | DOI Listing |
Angew Chem Int Ed Engl
December 2024
Shandong University, Chemistry and Chemical Engineering, Shanda South Road 27, 250100, Jinan, CHINA.
Catalytic transformation of carbene species constitutes a fundamental part in organic synthesis, and the research in this direction has been dominated by transition metals while organic catalysts are difficult to mimic such transition-metal-like reactivity. It would significantly advance carbene chemistry if organic catalysts enable achieving classical metal-carbene approaches otherwise unrealizable reactions. Herein, we report that chalcogen bonding catalysis can solve reactivity problem to achieve an elusive Buchner ring expansion of aryl ketones appending a cyclopropene moiety as carbene precursor.
View Article and Find Full Text PDFIron (Fe) availability limits photosynthesis at a global scale where Fe-rich photosystem (PS) I abundance is drastically reduced in Fe-poor environments. We used single-particle cryo-electron microscopy to reveal a unique Fe starvation-dependent arrangement of light-harvesting chlorophyll (LHC) proteins where Fe starvation-induced TIDI1 is found in an additional tetramer of LHC proteins associated with PSI in and . These cosmopolitan green algae are resilient to poor Fe nutrition.
View Article and Find Full Text PDFAdv Mater
December 2024
Institute of Physical Chemistry, Justus Liebig University Giessen, Heinrich-Buff-Ring 17, D-35392, Giessen, Germany.
Silicon is a promising negative electrode material for solid-state batteries (SSBs) due to its high specific capacity and ability to prevent lithium dendrite formation. However, SSBs with silicon electrodes currently suffer from poor cycling stability, despite chemical engineering efforts. This study investigates the cycling failure mechanism of composite Si/LiPSCl electrodes by decoupling the effects of interface chemical degradation and mechanical cracking.
View Article and Find Full Text PDFPolymers (Basel)
November 2024
Faculty of Chemistry, Lomonosov Moscow State University, Lenin Hills, 1, Bld. 3, 119991 Moscow, Russia.
The simple approach of increasing the elastic properties of atactic poly(propylene carbonate) (PPC) with Mn = 71.4 kDa, ĐM = M/M = 1.86, and predominantly carbonate units (>99%) is suggested by selecting the appropriate hot pressing temperature for PPC between 110 and 140 °C.
View Article and Find Full Text PDFAcc Chem Res
December 2024
Department of Chemistry, Northeast Normal University, Changchun 130024, China.
ConspectusIn the past decade, single-atom skeletal editing, which involves the precise insertion, deletion, or exchange of single atoms in the core skeleton of a molecule, has emerged as a promising synthetic strategy for the rapid construction or diversification of complex molecules without laborious synthetic processes. Among them, carbene-initiated skeletal editing is particularly appealing due to the ready availability and diverse reactivities of carbene species. The initial endeavors to modify the core skeleton of heteroarenes through carbon-atom insertion could date back to 1881, when Ciamician and Denstedt described the conversion of pyrroles to pyridines by trapping haloform-derived free carbene.
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