Science China Chemistry最新文献

Developing a new type of photocatalyst (PC) and catalytic mechanism for near-infrared (NIR) photocontrolled reversible-deactivation radical polymerization (RDRP) system is charming but challenging. Herein, a novel PC of the persistent radical anion (PRA) (possessing the properties of both radical and anion) was developed for NIR photocontrolled reversible addition-fragmentation chain transfer (RAFT) polymerization, enabling successful polymerization while gaining a deep insight into the mechanism of photo-induced electron transfer RAFT (PET-RAFT) polymerization. Different from the conventional and well-accepted reductive quenching (RQ) pathway, in which the radical anion intermediates of PCs (PCs^•−) must be generated in an excited state (ES), here, the PRA (3,4,9,10-perylenetetracarboxylic dianhydride radical anion (PTCDA^•−)) could generate conveniently in situ in the ground state (GS) and subsequently serve as highly efficient PC in the NIR region (740–850 nm). The successful implementation of this strategy elucidates the peculiar role played by light and the real way of electron transfer behaviors. In fact, the transfer of a single electron from PRA to chain transfer agent (CTA) and cleavage of the C–S bonds is a process from ES to GS, rather than always from GS (PCs^•−) to GS (CTA) in the RQ pathway as is well known to all. In addition, the excellent spatial-temporal control and powerful penetration ability of the NIR light were also confirmed by this PRA-catalyzed polymerization system.

We disclose the development of the Rh-catalyzed amine-directed remote 5,6-carboamination protocol of pyridines via dual Csp²–H functionalizations. A variety of readily available 2-aminopyridines and 1,2,3-triazoles are allowed for coupling cyclization to access polyfunctionalized azaindoles. Mechanistic studies including DFT calculations unveil that relay carbenoid-electrophilic addition to pyridines and the sequential pyridyl Csp²–H amination are involved in this transformation. The post-synthetic utility of this methodology is showcased by versatile and site-selective modification of azaindoles.

Construction of axially chiral 1-azafluorenes via nickel-catalyzed [2+2+2] cycloaddition of alkynes and (o-alkynyl)benzyl nitriles is described. This strategy enables enantioselective discrimination of two sterically similar ortho substituents, such as H and F, during the construction of tri-ortho-substituted biaryl atropisomers. Mechanistic studies including the stereochemistry model and the stability of the atropenantiomers toward racemization are provided. The unique steric hindrance provided by 1-azafluorene skeleton and the fine chiral cavity of the nickel catalyst are key to achieving high enantioselectivity.

Dihydropyran (DHP) compounds are not only found in natural products and bioactive molecules, but also serve as important precursors in organic synthesis. Nonetheless, traditional methods for the construction of such compounds are usually limited to disubstituted DHPs. To address this synthetic challenge, reported here is an efficient electrochemical strategy toward the selenated and trifluoromethylated DHP compounds. The reaction proceeded smoothly under mild electrolysis conditions. The broad substrate scope (>50 examples) and scalable synthesis demonstrated the complexity-building potential of the strategy. Initial mechanistic studies reveal that cyclization may involve a radical process. This protocol may promote the further development of diversified synthesis of multi-substituted dihydropyran.

Single-cell multi-omics technologies have thrived in recent years. The combined studies of different modalities in single cells have enabled comprehensive insights into the complex functional networks of vital biomacromolecules, thus paving the way for a thorough understanding of cell biology and pathology. In this review, we focus on the advances of single-cell multi-omics technologies utilizing sequencing strategies and propose potential perspectives.

DNA devices that can recognize molecular inputs and transform them into functional outputs in an autonomous manner have been actively pursued as versatile toolkits for controlled nanofabrication, molecular network regulation, biosensing and cellular function modulation. The introduction of external stimuli-responsive units not only ensures the programmability and functionality of DNA devices themselves, but also confers rapid, remote and reversible dynamic regulation capabilities. This facilitates on-demand activation and expands the application scope of dynamic DNA devices. Herein, an overview of recent advances in the construction of stimuli-responsive DNA devices that respond to different exogenous triggers, including physical stimuli (e.g., light, thermal, magnetic field, and electric field), chemical stimuli (e.g., supermolecules, pH, redox, and metal ions), and biological cues (e.g., protein, biomolecule, and nucleic acid), and their controllable nanofabrication and biomedical application have been provided. The current challenges and potential solutions of these externally responsive DNA devices for their future advancements in this emerging field are also discussed.

We developed a highly selective and efficient multicomponent transformation by utilizing alkynes and olefins/(hetero)arenes through photoinduced energy-transfer catalysis. The reaction involves the formation of three distinct chemical bonds, namely C(sp³)–C(sp²), C(sp²)–C(sp³), and C(sp³)–N, in a single coordinated manner. The strategy used a vinyl radical-mediated radical relay approach under mild conditions, exhibiting a broad substrate scope (>70 examples), excellent functional-group tolerance, and remarkable regio- and anti-stereoselectivity. Through the utilization of a combination of experimental techniques and density functional theory (DFT), we delved deeper into the mechanistic intricacies of this distinctive system. Results revealed that the selective radical addition to electron-deficient alkynes, rather than olefins, was governed by the inherent reactivity of alkyl radicals. This discovery presented a highly effective approach for the synthesis of stereodefined multisubstituted alkenes.

Vascular endothelium can perceive fluid shear stress (FSS) and cyclic circumferential stretch (CCS) caused by the pulsatile blood flow, and translate the hemodynamics into biochemical signals to regulate vascular pathophysiology. However, existing methods provide little information about the real-time biochemical responses of endothelium when exposed to dynamic FSS and CCS. Herein, a vasculature-on-a-chip integrated with stretchable sensing is engineered for recapitulating the hemodynamic milieus and in-situ monitoring biochemical responses of endothelial monolayer. The integrated device is developed by sandwiching a robust stretchable electrode between an upper fluidic channel and a lower pneumatic channel. The fluidic and pneumatic channels enable the simultaneous recapitulation of both FSS and CCS, and the integrated sensor exhibits excellent cell-adhesive capacity and electrochemical sensing stability even after long-term hemodynamic exposure. These allow real-time monitoring of hemodynamic form- and duration-dependent endothelium responses, and further efficacy investigation about a recommended drug for COVID-19, demonstrating the great potential in vascular disease and drug screening.

Transforming carbon dioxide (CO₂) into products using renewable electricity is a crucial and captivating quest for a green and circular economy. Compared with commonly used alkali electrolytes, acidic media for electrocatalytic CO₂ reduction (CO₂RR) boasts several advantages, such as high carbon utilization efficiency, high overall energy utilization rate, and low carbonate formation, making it a compelling choice for industrial applications. However, the acidic CO₂RR also struggles with formidable hurdles, encompassing the fierce competition with the hydrogen evolution reaction, the low CO₂ solubility and availability, and the suboptimal performance of catalysts. This review provides a comprehensive overview of the CO₂RR in acidic media. By elucidating the underlying regulatory mechanism, we gain valuable insights into the fundamental principles governing the acidic CO₂RR. Furthermore, we examine cutting-edge strategies aimed at optimizing its performance and the roles of reactor engineering, especially membrane electrode assembly reactors, in facilitating scalable and carbon efficient conversion. Moreover, we present a forward-looking perspective, highlighting the promising prospects of acidic CO₂RR research in ushering us towards a carbon-neutral society.