Synthesis of α-Trifluoromethyl Alkynes through Fluoroalkynylation of gem-Difluoroalkenes.

A trifluoromethylalkynylation reaction of gem-difluoroalkenes with alkynyl sulfoxide by photoredox radical addition with good functional group tolerance in moderate to high yields, is developed for the synthesis of α-trifluoromethyl alkyne. This reaction features simple operation and inexpensive raw materials and provides an expeditious route to synthesize biologically relevant fluorine-containing alkynyl compounds with diverse structural skeletons.

Recent Advances in Two-Photon AIEgens and Their Application in Biological Systems.

Two-photon fluorescence imaging technology has the advantages of high light stability, little light damage, and high spatiotemporal resolution, which make it a powerful biological analysis method. However, due to the high concentration or aggregation state of traditional organic light-emitting molecules, the fluorescence intensity is easily reduced or disappears completely, and is not conducive to optimal application. The concept of aggregation-induced emission (AIE) provides a solution to the problem of aggregation-induced luminescence quenching (ACQ), and realizes the high fluorescence quantum yield of luminescent molecules in the aggregation state. In addition, two-photon absorption properties can readily be improved just by increasing the loading content of AIE fluorogen (AIEgen). Therefore, the design and preparation of two-photon fluorescence probes based on AIEgen to achieve high-efficiency fluorescence imaging in vitro/in vivo has become a major research hotspot. This review aims to summarize representative two-photon AIEgens based on triphenylamine, tetraphenylethene, quinoline, naphthalene and other new structures from the past five years, and discuss their great potential in bioimaging applications.

Color-Tunable Light-up Bioorthogonal Probes for In Vivo Two-Photon Fluorescence Imaging.

Light-up bioorthogonal probes have attracted increasing attention recently due to their capability to directly image diverse biomolecules in living cells without washing steps. The development of bioorthogonal probes with excellent fluorescent properties suitable for in vivo imaging, such as long excitation/emission wavelength, high fluorescence turn-on ratio, and deep penetration, has been rarely reported. Herein, a series of azide-based light-up bioorthogonal probes with tunable colors based on a weak fluorescent 8-aminoquinoline (AQ) scaffold were designed and synthesized. The azido quinoline derivatives are able to induce large fluorescence enhancement (up to 1352-fold) after click reaction with alkynes. In addition, the probes could be engineered to exhibit excellent two-photon properties (δ=542 GM at 780 nm) after further introducing different styryl groups into the AQ scaffold. Subsequent detailed bioimaging experiments demonstrated that these versatile probes can be successfully used for live cell/zebrafish imaging without washing steps. Further in vivo two-photon imaging experiments demonstrated that these light-up biorthogonal probe outperformed conventional fluorophores, for example, high signal-to-noise ratio and deep tissue penetration. The design strategy reported in this study is a useful approach to realize diverse high-performance biorthogonal light-up probes for in vivo studying.

2-Styrylquinoline-based two-photon AIEgens for dual monitoring of pH and viscosity in living cells.

A new class of aggregation-induced emission (AIE) fluorophores HAPHs with excellent two-photon properties is developed from styrylquinoline. Among them, the probe HAPH-1 exhibits good sensitivity towards pH and viscosity and has been successfully used for simultaneous pH and viscosity detection in living cells through two-photon microscopy.

A novel chemiluminescent probe for hydrazine detection in water and HeLa cells.

Hydrazine is a substance harmful to humans and the environment, necessitating the development of a sensitive and specific detection method. Herein, a novel chemiluminescent probe based on Schaap's adamantylidene-dioxetane (CL-HZ) for detecting hydrazine was synthesized and evaluated. The probe was activated by the removal of a protecting group to form free phenoxy-dioxetane, when treated with hydrazine. It then showed a noticeable and sustainable fluorescent response without excitation, with intensity increasing 51-fold in the presence of hydrazine. CL-HZ can be used in 96-well high-throughput assays for analysis of hydrazine in polluted water samples and was successfully applied for the detection of hydrazine in living cells.

Late-Stage Direct o-Alkenylation of Phenols by PdII -Catalyzed C-H Functionalization.

o-Alkenylation of unprotected phenols has been developed by direct C-H functionalization catalyzed by PdII . This work features phenol group as a directing group and realizes highly site-selective C-H bond functionalization of phenols to achieve the corresponding products in moderate to excellent yields at 60 °C. The advantages of this reaction include unprecedented C-H functionalization using phenol as a directing group, high regioselectivity, good substrate scope, mild reaction conditions, and high efficiency. To the best of our knowledge, this is the first example of a regioselective C-H alkenylation of unprotected phenols utilizing phenolic hydroxyl group as a directing group. The alkenylation of unprotected tyrosine and intramolecular cyclization are also successfully carried out under this catalytic system in good yields. Furthermore, this novel method enables a late-stage modification of complex phenol-containing bioactive molecules toward a diversity-oriented drug discovery.

A novel lysosome-targeted fluorogenic probe based on 5-triazole-quinoline for the rapid detection of hydrogen sulfide in living cells.

A fluorogenic probe based on the novel fluorophore 5-triazole-quinoline was developed for the detection of hydrogen sulfide, an endogenous signaling molecule associated with the development of various diseases. The lysosome-targeted probe Lyso-HS was synthesized via C-H direct azidation from 8-aminoquinoline; it was able to detect H2S in 1 min and exhibited excellent turn-on ability with 95-fold fluorescence enhancement based on a new fluorochrome. The high quenching efficiency was further verified using time-dependent density functional theory (TDDFT). The probe also exhibited high selectivity and a low detection limit (as low as 214.5 nM), which has practical applications for disease detection and monitoring.

Correction: A highly selective ratiometric fluorescent probe for the cascade detection of Zn2+ and H2PO4 - and its application in living cell imaging.

[This corrects the article DOI: 10.1039/C7RA08020D.].

Regioselective and Direct Azidation of Anilines via Cu(II)-Catalyzed C-H Functionalization in Water.

We report herein the first example of Cu(II)-catalyzed site selective azidation of aromatic amines via C-H functionalization in aqueous media. In our strategy, a mild reagent was utilized. H2O2 served as the oxidant, and sodium azide was used as the azidation reagent. This method could also be applied to late-stage functionalization of drugs that possess an aromatic amine moiety. In addition, we found that bromination or iodination on the ortho-position of aromatic amines could occur efficiently using this catalytic system.