Angewandte Chemie最新文献

Coupling hydrogenation and dehydrogenation is of great significance, as both are pivotal bond reconstruction modes and co-occur in about 10% of chemical syntheses. However, stoichiometric imbalance often necessitates exogenous hydrogen, which causes “seesaw effect” and inhibits dehydrogenation, challenging thermodynamics and kinetics of tandem process. Herein, we propose a dynamic strategy based on chemical looping to modulate hydrogen species. We designed Ru_n@NiCu-V_M catalyst with metal vacancy (V_M) induced “electron allocator” properties, enabling reversible electron capture and release via chemical looping, which drives the neutral H· to convert into H⁻&H⁺, while simultaneously completing electron cycling. The converted H⁻&H⁺ promote hydrogenation of polar ─C═N bonds in the tandem reaction of 5-hydroxymethylfurfural to 2,5-furandimethanamine, while neutral H· enhances the dehydrogenation rate by avoiding charge repulsion with H⁻&H⁺ generated from dehydrogenation of ─CH₂OH. The coupled hydrogenation-dehydrogenation process achieves a 1.7-fold rate enhancement, delivers 92% 2,5-furandimethanamine yield, outperforms most reported catalysts, and exhibits broad substrate applicability.

Ni: neue Lösung für asymmetrische C(sp³)-H-Aktivierung.

Die stereoselektive Synthese vollständig kohlenstoffsubstituierter quartärer Stereozentren gelingt durch eine enantioselektive C(sp³)-H-Arylierung unter Verwendung eines Ni-Katalysators auf der Basis eines BINOL-Derivaten. Das rationale Design des katalytischen Zyklus erschließt einen neuen Reaktionsweg, der während des stereoselektiven und geschwindigkeitsbestimmenden Metallisierungsschritts effizient chirale Information induzieren kann.

While methodologies for N─O bond scission in O-functionalized oximes are well established, the analogous activation of free oximes remains challenging, largely due to the formidable hurdles associated with selective N─O bond cleavage and competing side reactions involving the acidic O─H moiety. Herein, we report a dual photo- and copper-catalyzed strategy that directly promotes homolytic cleavage of the N─O bond in free oximes through photosensitization of oxime-ligated copper complexes, thereby overcoming prior limitations. Mechanistic studies, including full characterization of key copper intermediates, support an energy transfer (EnT) pathway. This distinctive activation mode enables a previously elusive intermolecular cyclization between unprotected oximes and alkenes, delivering valuable 1-pyrrolines with high efficiency.

Leveraging the high reactivity, modularity, and orthogonality of the S(VI)-fluoride exchange (SuFEx) reaction, a new addition to click chemistry, we report here the SuFEx iterative exponential growth (SuFEx IEG) method for synthesizing uniform polymers and block copolymers (BCPs) with molecular weights up to 21 kDa. The key step in SuFEx IEG was the on-demand, orthogonal activation of the pair of functional groups, the SuFEx-inactive tetrahydropyranyl and imidazylate groups, into SuFEx-active tert-butyldimethylsilyl (TBS) and sulfonyl fluoride. With SuFEx IEG, we demonstrate the synthetic encoding of 16-bit information into the sequence-defined polysulfate of diphenyl sulfide and diphenyl ether. The modular nature of the SuFEx click reaction enabled the synthesis of uniform polysulfates, including hydrophilic oligo(ethylene glycol)-based polysulfates, that served as modules to create block copolymers (BCPs) and triblock copolymers without molecular weight distribution. The chain ends of the polymers and BCPs produced via SuFEx IEG were used to prepare uniform cyclic polymers and BCPs via intramolecular SuFEx cyclization. The SuFEx IEG method provides a robust and versatile approach for precisely constructing uniform linear and cyclic polymers, as well as sequence-defined polymers, across a broad molecular weight range.

Ni: neue Lösung für asymmetrische C(sp³)-H-Aktivierung.

Die stereoselektive Synthese vollständig kohlenstoffsubstituierter quartärer Stereozentren gelingt durch eine enantioselektive C(sp³)-H-Arylierung unter Verwendung eines Ni-Katalysators auf der Basis eines BINOL-Derivaten. Das rationale Design des katalytischen Zyklus erschließt einen neuen Reaktionsweg, der während des stereoselektiven und geschwindigkeitsbestimmenden Metallisierungsschritts effizient chirale Information induzieren kann.

Coupling hydrogenation and dehydrogenation is of great significance, as both are pivotal bond reconstruction modes and co-occur in about 10% of chemical syntheses. However, stoichiometric imbalance often necessitates exogenous hydrogen, which causes “seesaw effect” and inhibits dehydrogenation, challenging thermodynamics and kinetics of tandem process. Herein, we propose a dynamic strategy based on chemical looping to modulate hydrogen species. We designed Ru_n@NiCu-V_M catalyst with metal vacancy (V_M) induced “electron allocator” properties, enabling reversible electron capture and release via chemical looping, which drives the neutral H· to convert into H⁻&H⁺, while simultaneously completing electron cycling. The converted H⁻&H⁺ promote hydrogenation of polar ─C═N bonds in the tandem reaction of 5-hydroxymethylfurfural to 2,5-furandimethanamine, while neutral H· enhances the dehydrogenation rate by avoiding charge repulsion with H⁻&H⁺ generated from dehydrogenation of ─CH₂OH. The coupled hydrogenation-dehydrogenation process achieves a 1.7-fold rate enhancement, delivers 92% 2,5-furandimethanamine yield, outperforms most reported catalysts, and exhibits broad substrate applicability.

While methodologies for N─O bond scission in O-functionalized oximes are well established, the analogous activation of free oximes remains challenging, largely due to the formidable hurdles associated with selective N─O bond cleavage and competing side reactions involving the acidic O─H moiety. Herein, we report a dual photo- and copper-catalyzed strategy that directly promotes homolytic cleavage of the N─O bond in free oximes through photosensitization of oxime-ligated copper complexes, thereby overcoming prior limitations. Mechanistic studies, including full characterization of key copper intermediates, support an energy transfer (EnT) pathway. This distinctive activation mode enables a previously elusive intermolecular cyclization between unprotected oximes and alkenes, delivering valuable 1-pyrrolines with high efficiency.

The development of high-performance water-resistant and underwater adhesives is critical for advancing underwater technologies, yet achieving robust functional adhesion with long-term durability in complex underwater environments remains a significant challenge. Here, we present a hierarchical bonding network strategy to realize stable adhesion under harsh underwater conditions. By engineering a cross-linked polysiloxane backbone embedded with dense active interaction sites, including hydroxyl groups, benzene rings, cations, and hydrophobic moieties, we create synergistic multiscale interactions that amplify both cohesion and interfacial adhesion. The optimized adhesive achieves a strong bonding strength of 12.2 MPa and an underwater adhesion of 3.4 MPa on steel substrates and retains stability in corrosive underwater environments (acidic, alkaline, and saline solutions) over extended periods. It further demonstrates exceptional thermal resilience, maintaining functionality across temperatures from -196 to 150 °C. Integrating quaternary ammonium cations with long-chain alkanes endows the material with potent antibacterial activity (≥99.9999% inhibition) and the highest antifungal grade. This work provides a new avenue for designing high-performance multifunctional adhesives with strong adhesion, long-term durability, extreme temperature resistance, and antimicrobial properties, offering broad potential for applications in demanding underwater environments.

Catalytically active phase depends strongly on reaction conditions. In CO₂ hydrogenation, efforts have largely emphasized CO₂ activation while overlooking how to design active phase for the co-conversion of CO₂ and the kinetically distinct byproduct CO. Here, it is found that adding CO to CO₂–H₂ feeds boosts methanol productivity by up to 2.2-fold via a pronounced synergistic promotion of both CO₂ and CO hydrogenation over a Cu–ZnZrO_x catalyst. In situ spectroscopy reveals that CO accelerates Zn reduction and migration onto Cu, increasing Zn⁰/Cu ratio, Zn²⁺/Cu, and Cu⁺/Cu fraction, while reducing exposed surface Cu from 42% to 19%. This CO-induced restructuring enriches Zn exposure, drives CuZn alloy formation, and creates abundant CuZn alloy–ZnO_x interfaces that stabilize Cu⁺ sites. These interfaces enable a cooperative dual-pathway mechanism: CO₂ is hydrogenated mainly via the formate route at alloy–ZnO_x sites, whereas CO follows the formyl route on Cu sites. Additionally, in situ-formed water accelerates conversion of the rate-determining CH₃O^* intermediate in the CO pathway. Together, CO-driven evolution of active sites, synergistic dual-pathway catalysis, and water-assisted promotion yield highly efficient methanol synthesis from mixed CO–CO₂ feeds.

Polynuclear metal clusters can be potentially high-performance catalysts for the CO₂ reduction owing to the unique spatial structures among multiple active centers. Herein, two 30-nuclear doughnut-like lanthanide clusters (Eu30 and Dy30) were synthesized via in situ tandem reaction following a stepwise annular growth mechanism. In contrast to the Dy-based analog, Eu30 serves as a high-performance catalyst in visible-light-driven CO₂-to-CO conversion with 98% selectivity and a record-high turnover number reaching 1.720 × 10⁷, a rare case with only lanthanide metals as the active centers. Experimental and computational results indicate that the excellent performance of Eu30, as the first example of pure lanthanide cluster catalyst, can be attributed to its high redox activity with an appropriate LUMO energy level.