Chinese Journal of Chemistry最新文献

Poly(lactic-co-glycolic acid) (PLGA) has been widely employed for various biomedical applications owing to its biodegradability and biocompatibility. Particularly, the highly alternating PLGA exhibits a desirable degradation profile, making it an advanced platform for biomedical applications. In this contribution, we established a robust binary catalytic system of MTBD (7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene) and TU1 (1,3-bis(3,5-bis(trifluoromethyl)phenyl)thiourea), which facilitated highly regioselective ring-opening polymerization (ROP) of methyl glycolide (MG) to deliver PLGA with regioselectivity up to 90% at room temperature. Remarkably, a 1 : 1 blend of alt-PLGA samples prepared from (S)-MG and (R)-MG formed a stereocomplex (sc-PLGA) with T_m of 178 °C. Preliminary in situ ¹H NMR study revealed the ring opening from the lactyl side. We believe a dual activation mechanism via hydrogen-bonding interaction accounts for the improved regioselectivity.

This study successfully designed and synthesized two wide-bandgap donor-acceptor (D-A) copolymers, XY-1 and XY-2 with newly synthesized, low-cost ester-substituted benzotrithiophene as the acceptor unit, difluoro-substituted thiophene or bithiophene as the donor unit, respectively. XY-1 exhibits more rotational sites and poorer molecular planarity compared to XY-2, allowing the polymer backbone to rotate to some extent. These molecular properties resulted in not only appropriate phase separation size during the blending film formation process, but also optimal crystallinity, favorable molecular orientation, and excellent transport properties. In contrast, XY-2 exhibits conformational rigidity stemming from intramolecular F···S noncovalent interactions, resulting in detrimental phase segregation and compromised charge transport efficiency. Consequently, XY-1:L8-BO-based organic solar cells (OSCs) achieved an outstanding power conversion efficiency of 16.04 %, outperforming the XY-2-based OSCs. This work emphasizes the significance of regulating the stacking orientation and crystallinity of polymers to improve device performance, thereby offering valuable guidance for the future development of organic photovoltaics.

Mechanochromic mechanophores that operate in the near-infrared (NIR) region are highly desirable for applications requiring deep tissue penetration, high signal-to-noise ratio, and low background interference. However, most rhodamine-based mechanophores exhibit optical responses confined to the visible region. Herein, we report the design and synthesis of a benzothiophene-conjugation-extended NIR rhodamine mechanophore, termed 2XR-Rh. Theoretical calculations (constrained geometry simulates external force) and small-molecule model studies confirm that 2XR-Rh undergoes selective C–N bond cleavage under mechanical force, with the ring-opened form displaying a significantly red-shifted absorption maximum at 727 nm and emission at 777 nm, compared to conventional rhodamine mechanophores. When incorporated into linear polymethacrylates via single-electron transfer living radical polymerization (SET-LRP), 2XR-Rh exhibits force-dependent, efficient ultrasound-induced ring-opening. More importantly, in double-network elastomers containing polar monomers (2-hydroxyethyl acrylate/2-methoxyethyl acrylate), the mechanophore shows pronounced mechanochromic and mechano-fluorogenic responses under both tensile and compressive loading, enabling visual and fluorescence-based stress sensing in the solid state. This work demonstrates that benzothiophene-based π-extension is an effective strategy to push rhodamine mechanophores into the NIR region while retaining excellent force-responsiveness and thermal reversibility, offering a promising platform for advanced stress-sensing materials.

Pyrroles are privileged heterocycles in both natural systems and industrial applications, serving as key structural motifs in bioactive molecules, functional materials, pharmaceuticals, agrochemicals, and catalysts, which has driven continuous efforts to develop efficient synthetic methodologies for structurally diverse five-membered azacyclic derivatives. Ring expansion with carbynyl cation equivalents enables the selective reshaping of pre-existing molecular scaffolds with remarkable step economy, given that the capacity of carbynyl cations to form three new covalent bonds on a single carbon atom in one step. Carbynyl cation equivalents have been widely employed in ring expansion reactions to afford aromatic products, predominantly via [2+1] cycloaddition with unsaturated cyclic scaffolds or ylide formation with aromatic heteroatom. However, ring expansion reactions that proceed via ylide formation from carbynyl cation equivalents remain limited, and the use of saturated rings to construct aromatic skeletons still remains unexplored. Ring expansion of 3-alkylideneazetidines provides a direct route to five-membered azacycles, but this transformation remains greatly confined to noble metal catalysts and the synthesis of non-aromatic azacycles. Herein, we report a UV-light-induced ring expansion of chlorodiazirines as carbynyl cation equivalents with 3-alkylideneazetidines, proceeding via ammonium ylide formation to afford 1,2,4-trisubstituted pyrroles in moderate to good yields. The reaction exhibits broad compatibility with substrates bearing diverse electronic properties. Control experiments suggested that both singlet and triplet α-chlorocarbenes could be involved in this reaction. Possible mechanisms for this reaction involve ammonium ylide formation and ring expansion through direct or stepwise diradical/ion-pair pathways, followed by elimination and aromatization to afford the product. The utility of this protocol was substantiated by scalable synthesis and subsequent versatile diversification of the product into benzoyl-, formyl-, bromo-, and fully functionalized pyrrole derivatives. This transformation represents a unique example of aromatic skeleton construction through saturated azacycle expansion utilizing carbynyl cation equivalents. The catalyst- and base-free protocol features the advantages of mild reaction conditions, high step economy, and environmental friendliness.

The catalytic asymmetric synthesis of compounds exhibiting axial chirality has been extensively investigated over the past two decades and is now considered a mature area of research. In contrast, the construction of unplanarized atropisomeric scaffolds remains challenging due to their inherent configurational lability. Herein, we report a chiral phosphoric acid-catalyzed atroposelective Paal−Knorr reaction of N-aminoindolines with 1,4-diketones, enabling the construction of a new class of pyramidalized N–N atropisomers with high levels of stereoselectivities. A broad range of molecular motifs could be incorporated into this class of atropisomers, and the combination of scalable reaction with versatile post-synthetic modifications demonstrates the generality and robustness of the protocol. Single-crystal X-ray diffraction revealed the pyramidal nitrogen adopts a geometry between sp³- and sp²-hybridized states, while density functional theory calculations indicate that N–N axial chirality, rather than nitrogen-centered chirality, is the predominant stereogenic element. Preliminary biological evaluations indicated that several of these N–N axially chiral N-pyrrolylindolines exhibit promising inhibitory activity against tumor-cell proliferation. It is anticipated that this study will stimulate further development of novel axially chiral scaffolds.

Transition-metal-catalyzed C–H borylation is a powerful strategy for constructing C–B bonds, which are valuable intermediates in organic synthesis. However, many existing methods require precious metal catalysts, harsh conditions, or stoichiometric oxidants, and often demand strict exclusion of moisture and oxygen, limiting their practicality. Herein, we report a mild method for direct C(sp²)–H borylation of (hetero)arenes and perfluoroarenes using air as a green oxidant. The approach employs inexpensive FeCl₃ as a photocatalyst and chlorine radicals as hydrogen atom transfer (HAT) reagents. The transformation is driven by chlorine radicals generated via ligand-to-metal charge transfer (LMCT), which abstract hydrogen atoms from B–H bonds to form boryl radicals, thereby enabling subsequent C–B bond formation. Using only catalytic amounts of FeCl₃ and air as a green terminal oxidant, this strategy overcomes the limitations previously associated with oxygen radical mediated B–H activation. A key advantage of our protocol is its remarkable robustness under ambient conditions, requiring neither anhydrous solvents nor inert-atmosphere protection. Only a catalytic amount of FeCl₃ is needed, with air serving as the sole stoichiometric oxidant to regenerate the active iron species, thereby rendering the overall process atom-economical and waste-minimizing. The synthetic utility of this method was demonstrated by the successful preparation of a broad spectrum of (hetero)aryl and perfluoroaryl boronates bearing diverse functional groups. Furthermore, a one-pot, two-step Suzuki–Miyaura cross-coupling of perfluoroarenes was accomplished without intermediate isolation, affording biaryl products in good overall yields. This tandem procedure highlights the considerable industrial potential of our strategy for the sustainable synthesis of pharmaceuticals, agrochemicals, and advanced functional materials.

Glycosylation of bioactive molecules provides an attractive and efficient strategy to modulate their biological and pharmacological properties. Catalytic stereoselective N-glycosylation of sulfonamides to access medicinally relevant N-glycosyl sulfonamides represents an appealing yet challenging strategy for the direct structural diversification of sulfonamide scaffolds. Conventional synthetic methods generally rely on strong acids and exhibit high substrate dependence, insufficient regio- and stereocontrol, and exclusive access to only one-type of anomer, significantly restricting their general applicability. Herein, we present a stereodivergent, palladium-catalyzed N-glycosylation platform for the synthesis of a broad spectrum of N-glycosyl sulfonamides with high efficiency and excellent control over regioselectivity and stereoselectivity, using readily accessible pyranones as glycosyl donors. Remarkably, this approach enables efficient access to all four diastereomers of the N-glycosyl sulfonamides in excellent yields with complete regio- and stereocontrol. This mild protocol features broad substrate generality, excellent functional group compatibility, and facile scalability. The synthetic utility of this method is further demonstrated through a range of downstream synthetic transformations of the glycoside products. Collectively, this Pd-catalyzed glycosylation platform offers a general and precise strategy for the construction of valuable N-glycosyl sulfonamides, facilitating carbohydrate-based drug discovery.

DNA-encoded library (DEL) technology has emerged as a powerful platform for peptide drug discovery by enabling the rapid construction and screening of vast chemical space through on-DNA amino acid coupling. However, despite the critical role of unnatural amino acids (UAAs) in improving peptide stability, bioavailability, and target specificity, the limited availability of structurally diverse DNA-compatible UAA building blocks remains a major bottleneck for expanding the chemical diversity of DNA-encoded peptide libraries. Herein, we report a robust and DNA-compatible strategy for the on-DNA generation of dehydroalanine (Dha) through the mild elimination of DNA-conjugated cysteine under biocompatible conditions. Acting as a highly versatile synthetic linchpin, Dha enables the divergent installation of a broad spectrum of UAAs featuring sulfur-, nitrogen-, carbon-, phosphorus-containing, and cyclic side chains, thereby substantially enriching accessible peptide chemical space. Beyond serving as a diversification handle, the utility of this platform was demonstrated in multiple settings, including mock combinatorial peptide library synthesis, late-stage functionalization of bioactive peptide motifs, and on-DNA peptide macrocyclization, highlighting its broad synthetic scope and operational flexibility. Importantly, Dha also functions as an electrophilic covalent warhead for ligand-directed protein crosslinking, expanding its application beyond library diversification. Leveraging this unique reactivity, we further established a cysteine “unmasking” strategy that enables crosslinking-assisted DEL selection. As a proof of concept, a Dha-containing DEL screened against carbonic anhydrase II successfully identified target binders through covalent capture. Collectively, this work introduces a generalizable approach for expanding the structural diversity and functional complexity of DNA-encoded peptide libraries while integrating crosslinking-assisted selection capabilities, thereby providing new opportunities for peptide ligand discovery and covalent probe development.

Electrocatalytic two-electron oxygen reduction reaction (2 e^– ORR) represents a green and sustainable way for H₂O₂ production, while its practical applications in industry are largely hindered by the unwieldy proton transfer kinetics. Herein, we develop a biomimetic interface engineering strategy to precisely regulate proton transfer kinetics for enhanced 2 e^– ORR. Using atomically precise Au₂₅(p-MBA)₁₈ nanoclusters (NCs, p-MBA = 4-mercaptobenzoic acid) as model catalysts, we introduced a series of quaternary ammonium ionic liquid (IL) cations onto the cluster surface via combined electrostatic and π-π stacking interactions. The hydrophobic tails and controlled hydrolysis of IL cations disruptthe long-range interconnected hydrogen-bonding networks, which are ubiquitous in alkaline electrolytes and bring about an overwhelming proton transfer rate. Instead, a mild biomimetic proton relay mechanism favoring 2 e^– ORR can be established and fine-adjusted, leveraging deprotonation and protonation equilibrium of IL cations. By this way, the optimized system can bring down the mean electron transfer number (n) to 2.45 and promote the H₂O₂ selectivity to 90% or higher, evidencing a pronounced shift toward the 2 e^– ORR pathway under alkaline conditions. This work underscores the usefulness of atomically precise interfacial engineering in optimizing the electrocatalytic performance of inorganic nanocatalysts.