Low dielectric materials with high heat dissipation, low dielectric constant (Dk), and dielectric loss (Df) are urgently needed to address the issues of signal cross-talk and heat accumulation arising from the rapid development of modern communication technology and the integration of microelectronics. Polyolefins, as hydrocarbon polymers, have shown significant potential due to their excellent low dielectric properties. However, their low polarity and flexible structures limit their thermal conductivity and thermomechanical properties. In this study, we developed a method to prepare thermosetting polybutadiene composites with enhanced thermal conductivity and good dielectric performance by modifying hexagonal boron nitride (h-BN) and hydroxyl- terminated polybutadiene (HTPB) with thermally cross-linkable benzocyclobutene (BCB) groups. The properties of the resulting composites were tailored by varying the filler content. With 30 wt% of the BCB-modified filler, the composite (HB-30) displayed excellent dielectric properties (Dk = 2.70; D f = 1.67 x 10-3 @10 GHz). Meanwhile, it exhibited a thermal conductivity of 0.615 W/mK at 35 degrees C, which was 7.1 times that of pristine HTPB. It also showed significantly enhanced mechanical properties and thermal stability with a storage modulus of 2.7 GPa and a glass transition temperature (Tg) of 208.5 degrees C. This method proved effective for preparing polymer composites with enhanced thermal conductivity, heat resistance, mechanical properties and good dielectric properties, making them suitable for high-frequency communication applications.

The development of a nucleophilic fluorination protocol using hydrofluoric acid as the fluoride source represents a long-sought goal in the field of organofluorine chemistry. We report herein the realization of such a reaction that employed alkyl-substituted sulfonium ylides as the substrates. The key to the success of the protocol was attributed to two factors: First, as a Br & oslash;nsted base, the ylide was able to be protonated by HFaq, thus serving as a phase-transfer shuttle generated in situ to bring F- from aqueous phase to the organic phase promoting desolvation of fluoride ion. Second, after protonation, a sulfonium salt, a good leaving group, was generated and subsequent attacked by the fluoride to afford the alkyl fluoride. Mechanistic investigation indicates that the reaction occurs via an S(N)1 pathway. Because of the nature of the cationic intermediate in the reaction, two attractive rearrangement-fluorination approaches including 1,2-aryl migration fluorination and ring-expansion fluorination were disclosed.

The selective functionalization of carbohydrates holds a central position in synthetic carbohydrate chemistry, driving the ongoing quest for ideal approaches to manipulate these compounds. In this study, we introduce a general strategy that enables the regiodivergent functionalization of saccharides. The use of electron-deficient photoactive 4-tetrafluoropyridinylthio (SPyf) fragment as an adaptable activating group, facilitated efficient functionalization across all saccharide sites. More importantly, this activating group can be directly installed at the C1, C5 and C6 positions of biomass-derived carbohydrates in a single step and in a site-selective manner, allowing for the efficient and precision-oriented modification of unprotected saccharides and glycans.

Hydroxylated (hetero)arenes are privileged motifs in natural products, materials, small-molecule pharmaceuticals and serve as versatile intermediates in synthetic organic chemistry. Herein, we report an efficient Cu(I)/6-hydroxy picolinohydrazide-catalyzed hydroxylation reaction of (hetero)aryl halides (Br, Cl) in water. By establishing machine learning (ML) models, the design of ligands and optimization of reaction conditions were effectively accelerated. The N-(1,3-dimethyl-9H- carbazol-9-yl)-6-hydroxypicolinamide (L32, 6-HPA-DMCA) demonstrated high efficiency for (hetero)aryl bromides, promoting hydroxylation reactions with a minimal catalyst loading of 0.01 mol % (100 ppm) at 80 degrees C to reach 10000 TON; for substrates containing sensitive functional groups, the catalyst loading needs to be increased to 3.0 mol % under near-room temperature conditions. N-(2,7-Di-tert-butyl-9H-carbazol-9-yl)-6-hydroxypicolinamide (L42, 6-HPA-DTBCA) displayed superior reaction activity for chloride substrates, enabling hydroxylation reactions at 100 degrees C with 2-3 mol % catalyst loading. These represent the state of art for both lowest catalyst loading and temperature in the copper-catalyzed hydroxylation reactions. Furthermore, this method features a sustainable and environmentally friendly solvent system, accommodates a wide range of substrates, and shows potential for developing robust and scalable synthesis processes for key pharmaceutical intermediates.

Thiolate-ligated high-valent iron species are reactive intermediates in the C-H bond activation reactions of P450 and isopenicillin N synthase enzymes. Synthetic complexes of the type are rarely known. Presented herein are the synthesis and characterization of an iron(V) bisimido complex with thiolate ligation, viz. [(IPr)Fe(NC(CH3)(2)Ph)(2)(2-F-C6H4S)] (1, IPr = 1,3-bis(2 ',6 '-diisopropylphenyl)imidazol-2-ylidene) as well as the ionic iron(V) bisimido complex [(IPr)Fe(NC(CH3)(2)Ph)(2)][BAr4F] (2, BAr4F = tetra(3,5-ditrifluoromethylphenyl)borate). The two iron(V) complexes have been characterized by a single-crystal X-ray diffraction study and EPR and zero-field Fe-57 Mossbauer spectroscopy. The spectroscopic data and DFT calculations revealed their S = 1/2 ground spin states.

Metal-free synthesis of heterocycles is highly sought after in the pharmaceutical industry and has garnered widespread attention due to eliminating the need to remove trace metal catalysts from the reaction. We report a radical 6-endo addition method for pyridine synthesis from cyclopropylamides and alkynes under metal-free conditions. Various terminal and substituted alkynes are inserted as C2 units into cyclopropylamides to synthesize versatile pyridines with 57 examples. Mechanistic investigations and computational studies indicate the unprecedented 6-endo-trig addition of vinyl radicals to the imine nitrogen atom rather than the conventional 5-exo-trig addition to the imine carbon atom, in which the hypervalent iodine(III) plays a critical role. This reaction easily scales up with excellent functional group compatibility and suits the late-stage pyridine installation on complex molecules.

Spinal cord injury (SCI) triggers a cascade of intricate molecular and cellular changes that determine the outcome. In this study, we resolve the spatiotemporal organization of the injured mouse spinal cord and quantitatively assess in situ cell-cell communication following SCI. By analyzing existing single-cell RNA sequencing datasets alongside our spatial data, we delineate a subpopulation of Igfbp2-expressing astrocytes that migrate from the white matter (WM) to gray matter (GM) and become reactive upon SCI, termed Astro-GMii. Further, Igfbp2 upregulation promotes astrocyte migration, proliferation, and reactivity, and the secreted IGFBP2 protein fosters neurite outgrowth. Finally, we show that IGFBP2 significantly reduces neuronal loss and remarkably improves the functional recovery in a mouse model of SCI in vivo. Together, this study not only provides a comprehensive molecular atlas of SCI but also exemplifies how this rich resource can be applied to endow cells and genes with functional insight and therapeutic potential.