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Accurate detection of labile analytes through activity based fluorogenic sensing is meaningful but remains a challenge because of nonrapid reaction kinetic. Herein, we present a signaling reporter engineering strategy to accelerate azoreduction reaction by positively charged fluorophore promoted unstable anion recognition for rapidly sensing sodium dithionite (Na2S2O4), a kind of widespread used but harmful inorganic reducing agent. Its quick decomposition often impedes application reliability of traditional fluorogenic probes in real samples because of their slow responses. In this work, four azo-based probes with different charged fluorophores (positive, zwitterionic, neutral, and negative) were synthesized and compared. Among of them, with sequestration effect of positively charged anthocyanin fluorophore for dithionite anion via electrostatic attraction, the cationic probe Azo-Posdisplayed ultrafast fluorogenic response (∼2 s) with the fastest response kinetic (kpos′= 0.373 s–1) that is better than other charged ones (kzwi′= 0.031 s–1, kneu′= 0.013 s–1, kneg′= 0.003 s–1). Azo-Poswas demonstrated to be capable to directly detect labile Na2S2O4in food samples and visualize the presence of Na2S2O4in living systems in a timely fashion. This new probe has potential as a robust tool to fluorescently monitor excessive food additives and biological invasion of harmful Na2S2O4. Moreover, our proposed accelerating strategy would be versatile to develop more activity-based sensing probes for quickly detecting other unstable analytes of interest.

A strategy for the synthesis of α-carboline derivatives from indole-3-carboxaldehydes and 3-aminocyclohex-2-enones under metal-free conditions has been developed. The combination use of phenyliodine (III) diacetate (PIDA) and benzoic acid could significantly facilitate the corresponding [3 ​+ ​3] annulation process. This newly developed strategy featured unextraordinary chemoselectivity, good functional group tolerance and the preservation of the carbonyl group of the ketone substrates, which offers the possibility for further transformation of the products.

Acid phosphatase (ACP) is a ubiquitous phosphatase in living organisms. The abnormal variation of ACP is related to various diseases. Herein, we propose a colorimetric method based on CeO2-modified gold core shell nanoparticles (Au@CeO2NPs) to analyze ACP activity with high sensitivity and specificity. In this design, 2-phospho-L-ascorbic acid trisodium salt (AAP) is dephosphorylated by ACP and produces reductive ascorbic acid (AA), which makes the CeO2shell decomposition. A remarkable blue shift of localized surface plasmon resonance peak (LSPR, from yellow to green) along with the scattering intensity ratio changes from individual Au@CeO2NPs are observed. ACP activity can be quantified by calculating the ratio changes of individual Au@CeO2NPs. This assay reveals limit of detection (LOD) of 0.044 mU/mL and the linear range of 0.05–5.0 mU/mL, which are much lower than most of spectroscopic measurements in bulk solution. Furthermore, the recovery measurements in real samples are satisfactory and the capacity for practical application is demonstrated. As a consequence, Au@CeO2NPs used in this assay will find new applications for the ultrasensitive detection of enzyme activity.

An acetic acid-promoted C(sp3)-H functionalization of 2-methyl quinoline, enaminoesters and elemental sulfur for the synthesis of 3,4,5-trisubstituted isothiazoles under metal-free conditions has been developed. This approach provides viable access to various 5-(quinolin-2-yl)isothiazoles in moderate to good yields with good functional group tolerance. Moreover, the success of the gram-scale reaction gives this reaction a great potential application.

The endoplasmic reticulum (ER) is the most widespread organelle within eukaryotic cells, performing various essential functions such as protein synthesis, post-translational modifications, and lipid metabolism. Abnormal fluctuations of biologically active species and microenvironments in the ER can disrupt homeostasis and eventually lead to ER stress, which is closely linked to the occurrence and progression of many human diseases. Therefore, the ER has been regarded as an important analytical object as well as a promising therapeutic target in both bio sensing and biomedicine. Recently, there has been a growing interest in developing photon-excited molecular tools to uncover the physio pathological roles of ER and treat ER-related disorders. This review presents a comprehensive summary of recent advances in ER-targeted small-molecule probes and their applications for fluorescent sensing and phototherapy, mainly focusing on targeting strategies and probe design principles. Last, we discuss the challenges involved with ER-targeted probes and highlight potential prospects in this field.

A visible-light induced direct C(sp3)-H functionalization of alkylarenes with trifluoromethyl ketones has been reported to access valuable benzyl-substituted trifluoromethyl alcohols in a stoichiometric manner. Readily available petroleum-derived alkylarenes are employed as latent benzylation reagents. With a bromine radical as the hydrogen atom transfer reagent, primary, secondary, and tertiary benzyl C–H bonds are suitable coupling partners. Additionally, the late-stage modification of bioactive molecules highlights the potential application of this approach.

A three-component strategy was developed for 3-phenyl-9H-imidazo[1,5-a]indol-9-one preparation from indole-2-carboxaldehydes, aromatic aldehydes, and ammonium acetate under copper catalysis conditions. In this process, a new five-membered ring was formed and the C3 position in the indole substrate was selectively oxidized into a ketone skeleton using oxygen as the sole oxidant and ammonium acetate as the nitrogen source. Furthermore, same products also could be achieved from indole-2-carboxaldehydes and benzyl amines under similar reaction conditions.

A highly site-selective trifluoromethylaminoxylation of activated and unactivated olefins was reported under metal-free conditions. The method provides direct access to diverse β-trifluoromethyl trisubstituted hydroxylamines, tertiary alcohols, isoxazolines, isoxazolidines, and amino alcohols. The SET process between hydroxylamine and the hypervalent iodine–CF3reagent is proposed to produce two free radicals for the regio- and diastereoselective addition to alkenes. The synthetic potential of the protocol was established via the late-stage functionalization of the products and a series of postreaction modifications.

A metal-free method for the construction of 2-substituted quinolines and benzo[f]quinolines from aromatic amines, aldehydes, and tertiary amines has been demonstrated. Cheap and readily available tertiary amines acted as the vinyl source. A new pyridine ring was selectively formed via[4 + 2] condensation that was promoted by ammonium salt under neutral conditions and an oxygen atmosphere. This strategy provided a new route for the preparation of various quinoline derivatives with different substituents at the pyridine ring, which provides the possibility of further modification.

A CuBr2-catalyzed annulation of 2-bromo-N-arylbenzimidamide with selenium/sulfur powder for the synthesis of benzo[d]isoselenazole and benzo[d]isothiazole in generally good yields was investigated. This synthetic strategy features good substrate scope and functional group tolerance. Furthermore, the corresponding products could be converted into N-aryl indoles viarhodiumIII-catalyzed orthoC–H activation of the N-phenyl ring, providing an efficient approach for axial aromatic molecules.

A four-component synthesis of tetrasubstituted pyrroles was developed under metal-free conditions. The pyrrole ring was formed in one pot through [2 + 1 + 1 + 1] condensation using ammonium salt as the nitrogen source. In this strategy, 1,4-naphthoquinones and maleimides were used as the versatile C2 fragments to provide substituted benzo[f]isoindole-4,9-diones and pyrrolo[3,4-c]pyrrole-1,3-diones, respectively. This work is highlighted by using ammonium salt as the nitrogen source, readily available starting materials and multibond formation (two C–C and two C–N bonds) in a single operation.

Ultrathin organic polymer with p-π conjugated structure toward the selective dehydrogenative coupling of benzyl mercaptan to SS coupled products combined with CO2reduction has been constructed through a facile synthetic strategy.

A Pd-catalyzed C–O cross-coupling of O-acyl hydroxylamines and tertiary or secondary alkyl electrophiles was reported without the cleavage of the rather fragile N–O bond. The described strategy provides direct access to congested N,N,O-trisubstituted hydroxylamines bearing an α-quaternary carbon center under mild conditions in high yields and features exclusively chemoselective C–O bond formation, a broad substrate scope, and excellent functional group tolerance. The synthetic potential of the cross-coupling was established via pharmaceuticals derivatizations and a series of postcatalytic modifications.

We have reported a metal-free protocol for the synthesis of indenoquinolinones and 2-substituted quinolines via[4 + 2] cycloaddition reaction using readily available 2-aminobenzaldehydes and ketones as starting materials. Different quinoline derivatives can be selectively synthesized by changing the type of ketones. O2and dimethyl sulfoxide (DMSO) as co-oxidants play an important role in the synthesis of indenoquinolinones. This condensation/oxidation strategy involves the formation of C–N, C–C, and C–O bonds, with the advantages of high yields and a broad substrate range.

A novel strategy for the preparation of functional carbazoles through NaI-catalyzed formal [4 + 2] annulation of 2-(indol-3-yl)cyclohexanones and alkynes/alkenes has been developed. The present approach started from easily available raw materials and provided a variety of tetrahydrobenzo[c]carbazolones in satisfactory yields under metal- and solvent-free conditions. Furthermore, the products could be further transformed into structurally valuable carbazole-based conjugated derivatives.

The C–S bond formation from aryl halides and thiols has been well established under various catalytic systems. In this work, user-friendly sulfinates have been exploited as an efficient sulfenylating reagent in the C–S couplings through visible-light-induced photo/nickel dual catalysis under base- and external reductant-free conditions. A large number of aryl sulfide products were accessed with high selectivity and high tolerance of various functionalities.

The incorporation of gem-difluoromethylene units into organic molecules remains a formidable challenge. Conventional methodologies for constructing aryldifluoromethyl derivatives relied on the use of high-functional fluorinating regents under harsh conditions. Herein, we report general and efficient photoredox catalytic systems for defluoroalkylation of readily available trifluoromethylarenes through selective C–F cleavage to deliver gem-difluoromethyl radicals which proceed through reductive addition to both electron-donating and withdrawing alkenes under transition-metal free conditions. Mechanistic studies reveal that thiol serves as both photocatalyst and HAT reagent under visible light irradiation. This synergistic photocatalysis and HAT catalysis protocol exhibits ample and salient features such as high chemo- and regioselectivity, broad substrate scope, amenable gram-scale synthesis and late-stage modification of bioactive molecules.

Myrosinase (Myr), as a unique β-thioglucosidase enzyme capable of converting natural and gut bacterial metabolite glucosinolates into bioactive agents, has recently attracted a great deal of attention because of its essential functions in exerting homeostasis dynamics and promoting human health. Such nutraceutical and biomedical significance demands unique and reliable strategies for specific identification of Myr enzymes of gut bacterial origin in living systems, whereas the dearth of methods for bacterial Myr detection and visualization remains a challenging concern. Herein, we present a series of unique molecular probes for specific identification and imaging of Myr-expressing gut bacterial strains. Typically, an artificial glucosinolate with an azide group in aglycone was synthesized and sequentially linked with the probe moieties of versatile channels through simple click conjugation. Upon gut bacterial enzymatic cleavage, the as-prepared probe molecules could be converted into reactive isothiocyanate forms, which can further act as reactive electrophiles for the covalent labeling of gut bacteria, thus realizing their localized fluorescent imaging within a wide range of wavelength channels in live bacterial strains and animal models. Overall, our proposed method presents a novel technology for selective gut bacterial Myr enzyme labeling in vitroand in vivo. We envision that such a rational probe design would serve as a promising solution for chemoprevention assessment, microflora metabolic mechanistic study, and gut bacterium-mediated physiopathological exploration.

The unrepaired apurinic/apyrimidinic site (AP site) in mitochondrial DNA (mtDNA) promotes misincorporation of nucleotides and further causes serious damage for the living organism. Thus, accurate quantitative detection of AP sites in mtDNA in a rapid, highly sensitive, and highly selective fashion is important for the real-time evaluation of mtDNA oxidative damage. In this study, a targeting mtDNA ultrasensitive AP site-specific fluorescent rotor (BTBM-CN2) was designed by the strategy of molecular conformation torsion adjustment ratio fluorescent signal. The specific recognition reaction is activated when it encountered AP sites in mtDNA within 20 s, and BTBM-CN2presented a “turn-on” red fluorescence signal at 598 nm. Then, about 100 s later, BTBM-CN2emitted a new green fluorescence signal at 480 nm, which is mainly due to the activation of the rate-limiting reaction. With increasing numbers of AP sites (1–40 in 1 × 105bp of mtDNA), the fluorescence emission at 598 nm decreased gradually, and the new emission at 480 nm increased. Intracellular experiments indicated that BTBM-CN2could detect AP sites in mtDNA in a rapid and quantitative fashion with high selectivity and ultrasensitivity. On the basis of the emergence of the fluorescence signal at 480 nm and its signal strength, the cell whose mtDNA was damaged could be screened by flow cytometry and its degree of damage could be evaluated in real time by comet assay. Hence, the rotor may have potential applications varying from accurate and ultrasensitive detection of AP sites to the real-time evaluation of the oxidative damage in living cells.

Aerogels are attractive candidates in the field of oily wastewater treatment. Nevertheless, some disadvantages like sharp shrinkage, massive expense of drying process, and weak mechanical properties pose an obstacle to their wide practical applications. Herein, an activated carbon (AC) enhanced thermoplastic polyurethane (TPU-AC) composite aerogel was successfully prepared by simple thermally induced phase separation (TIPS) method followed by ambient pressure drying. The average drying shrinkage rate of TPU-AC was controlled to < 10% due to the AC-enhanced skeleton. With an optimal addition of AC, the resultant composite aerogel exhibited low density, reasonable porosity, and significantly improved specific surface area (105.86 m2/g). Good hydrophobicity endowed TPU-AC with superior oil/water selectivity. Therefore, an adequate oil adsorption capacity of up to 38.64 g/g was gained by TPU-AC with a fast adsorption rate. Thanks to the marvelous mechanical flexibility of TPU-AC, especially, the absorption and recovery of oil can be realized by facile adsorption-extrusion method as well as pump-assisted oil/water separation device with satisfactory separation efficiency and excellent recyclability. Along with the admirable cost effectiveness, the current study is expected to pave a facile way for aerogel preparation, providing a scalable and effective strategy for oily wastewater treatment.

In this work, we developed a novel fluorescent probe 1for quantitative detection of nitroxyl (HNO). Probe 1consisted of a naphthalene backbone and 2-(diphenylphosphino)benzoate which was used as a nitroxyl recognition unit. The probe exhibited an intense fluorescence turn-on response to nitroxyl viaaza-ylide formation and its subsequent Staudinger ligation to release compound 2. The probe can be applied to the quantification of nitroxyl with a linear range from 5.0 × 10−8to 9.0 × 10−6mol L−1. The detection limit of probe 1toward nitroxyl was estimated to be 43 nM. Furthermore, probe 1displayed a much higher selectivity for nitroxyl than other biologically relevant species. Importantly, owing to the high cell permeability and low cytotoxicity of probe 1, it was successfully applied to cell imaging of nitroxyl in living cells. The probe is expected to be a useful chemical tool for investigating the detailed functions and mechanisms of HNO in living systems.

The Pictet-Spengler/transamination cascade reaction enables modular synthesis of marinoquinoline analogues through three-component indole ring-expansion/cyclization in the manner of novel N1–C2 cleavage of indoles. This metal-free protocol exhibits very broad functional group tolerance with up to quantitative yields. Preliminary studies on the antitumor activity of the resultant marinoquinoline analogues reveal that the indolyl-attached pyrrolo[2,3-c]quinoline product (5d) shows great potential (IC50of 0.32 μg/mL to HeLa cells) as a promising anticancer agent in clinic.

A three-starting-material four-component reaction strategy is described to construct thienopyrrolediones (TPDs) from the simplest raw materials, elemental sulfur, aldehydes, and β-ketoamides, under transition metal free conditions. Compared with traditional multistep reaction sequences, this process is simple, efficient, environmentally friendly, and atom-economic and has laid the foundation for further development of an easily synthesized TPD unit.