For the first time we present nanoindentation analysis of charred, cured aromatic cyanate esters, which exhibit outstanding mechanical properties when analysed under applied loads of 0.1-300 mN. Following charring (900 °C for 10 minutes to achieve graphitised structures), the samples display a remarkable combination of a modulus of elasticity of around 25 GPa and nanohardness of 300 kgf mm, making them some 30-40% stiffer than bone and practically as hard as tooth enamel. At the same time we find that under the same conditions the chars are highly resilient, displaying complete elastic recovery with very little plastic deformation. When cured in the presence of copper(ii) acetylacetonate (200 ppm) in dodecylphenol (1% w/v active copper suspension) to form a polycyanurate, compound (2) forms a dense, consolidated structure compared with compound (1) under the same conditions. At high magnification, the presence of a nanoscale, fibrillar structure is observed, accounting for the high resilience.
A new electrochemical method is introduced for safer cyanation reactions using 5-aminotetrazole as a cyanide source, avoiding toxic cyanide salts.
This method successfully generates both electrophilic and nucleophilic cyanide sources and allows for the synthesis of various compounds like cyanamides, heterocycles, and aromatic nitriles.
The process has been adapted for flow electrosynthesis, showcasing its scalability and potential for large-scale use.*
Researchers used density functional theory to show that small polycyclic aromatic hydrocarbons containing odd-membered carbon rings can significantly reduce electron reorganization energies in n-type organic semiconductors.
They examined 60 molecules, finding that those with 5- and 7-membered rings incorporated into linear or nonlinear structures achieved very low reorganization energies (as low as 65 meV).
The study suggests that higher molecular aromaticity leads to lower energy levels and proposes specific areas ("acupoints") for modifications to enhance electron injection and stability without increasing reorganization energy.
Aryl thianthrenium salts are valuable in photocatalysis but traditionally require external electron donors for activation. This study introduces an energy transfer (EnT) strategy for the activation of aryl thianthrenium salts using 2,3,4,5,6-penta(carbazol-9-yl)benzonitrile (5CzBN) as a metal-free photocatalyst, eliminating the need for external donors. Utilizing this EnT approach, we achieve C-H deuteration of arenes under visible light with CDCl as a deuterium source to synthesize various deuterated aromatic compounds, including important natural products and pharmaceuticals.
SupraSelen Laboratory, Department of Organic Chemistry, Institute of Chemistry, Universidade Federal Fluminense, Campus do Valonguinho, Niterói, RJ, 24020-141, Brazil.
A novel strategy to catalyze alkylation reactions through chalcogen bond interaction using a supramolecular structure is presented herein. Utilizing just 1.0 mol % of selenoxide-pillar[5]arene (P[5]SeO) as the catalyst we achieved efficient catalysis in the cyanation of benzyl bromide in water.
ConspectusAromatic esters are cost-effective, versatile, and commonly used scaffolds that are readily synthesized or encountered as synthetic intermediates. While most conventional reactions involving these esters are nucleophilic acyl substitutions or 1,2-nucleophilic additions─where a nucleophile attacks the carbonyl group, decarbonylative transformations offer an alternative pathway by using the carbonyl group as a leaving group. This transition-metal-catalyzed process typically begins with oxidative addition of the C(acyl)-O bond to the metal.
