Asymmetric photoredox catalytic formal de Mayo reaction enabled by sensitization-initiated electron transfer.

Visible-light-driven photoredox catalysis is known to be a powerful tool for organic synthesis. Its occurrence critically depends on the twice exothermic single-electron transfer processes of photosensitizers, which are governed by the redox properties of the species involved. Hence, the inherently narrow range of redox potentials of photosensitizers inevitably constrains their further availability. Sensitization-initiated electron transfer has recently been found to effectively overcome this substantial challenge. However, feasible and practical strategies for designing such complicated catalytic systems are rather scarce. Herein we report an elaborate dual-catalyst platform, with dicyanopyrazine as a visible light photosensitizer and a pyrenyl-incorporated chiral phosphoric acid as a co-sensitizer, and we demonstrate the applicability of this sensitization-initiated electron transfer strategy in an asymmetric formal de Mayo-type reaction. The catalysis platform enables otherwise thermodynamically unfavourable electron transfer processes to close the redox cycle and allows for precise access to valuable enantioenriched 1,5-diketones with a wide substrate range.

[Research progress on pathogenic mechanism of sepsis-induced liver injury and treatment with traditional Chinese medicine and its active components].

Sepsis is a systemic inflammatory response syndrome caused by infection, with high morbidity and mortality. Sepsis-induced liver injury(SILI) is one of the manifestations of sepsis-induced multiple organ syndrome. At present, there is no recommended pharmacological intervention for the treatment of SILI. traditional Chinese medicine(TCM), based on the holism and dialectical treatment concept, shows the therapeutic characteristics of multi-target and multi-pathway and can comprehensively prevent and treat SILI by interfering with inflammatory factors, inflammatory signaling pathways, and anti-oxidative stress and inhibiting apoptosis. This article reviewed the experimental studies on the treatment of SILI with TCM to clarify its pathogenic mechanism and therapeutic characteristics, so as to provide more ideas and directions for the development or preparation of new drugs.

Radical Cross Coupling and Enantioselective Protonation through Asymmetric Photoredox Catalysis.

An unprecedented enantioselective protonation reaction enabled by photoredox catalytic radical coupling is developed. Under cooperative dicynopyrazine-derived chromophore (DPZ) as a photosensitizer and a chiral phosphoric acid catalyst, and Hantzsch ester as a sacrificial reductant, the transformations between α-substituted enones and cyanoazaarenes or 2-(chloromethyl)azaaren-1-iums can proceed a tandem reduction, radical coupling, and enantioselective protonation process efficiently. Two classes of pharmaceutically important enantioenriched azaarene variants, which contain a synthetically versatile ketone-substituted tertiary carbon stereocenter at the ß- or γ-position of the azaarenes, are synthesized with high yields and ees.

Visible-Light-Induced Cascade Cyclization of 1-Acryloyl-2-cyanoindole: Access of Difluoroalkylated Pyrrolo[1,2-a]indolediones.

An effective method for accessing diverse difluoroalkylated pyrrolo[1,2-a]indolediones via visible-light-induced PhI(OAc)2-promoted cascade difluoroalkylation/cyclization reaction under mild conditions has been established. This method is noteworthy for its use of DMSO-H2O as a green medium at room temperature and avoidance of photocatalysts. The reactions are straightforward to execute and convenient to expand on, provide good to excellent yields, and have good functional group tolerance.

Asymmetric Olefin Isomerization via Photoredox Catalytic Hydrogen Atom Transfer and Enantioselective Protonation.

Asymmetric olefin isomerization can be appreciated as an ideal synthetic approach to access valuable enantioenriched C═C-containing molecules due to the excellent atom economy. Nonetheless, its occurrence usually requires a thermodynamic advantage, namely, a higher stability of the product to the substrate. It has thus led to rather limited examples of success. Herein, we report a photoredox catalytic hydrogen atom transfer (HAT) and enantioselective protonation strategy for the challenging asymmetric olefin isomerization. As a paradigm, by establishing a dual catalyst system involving a visible light photosensitizer DPZ and a chiral phosphoric acid, with the assistance of N-hydroxyimide to perform HAT, a wide array of allylic azaarene derivatives, featuring α-tertiary carbon stereocenters and ß-C═C bonds, was synthesized with high yields, ees, and E/Z ratios starting from the conjugated α-substituted alkenylazaarene E/Z-mixtures. The good compatibility of assembling deuterium on stereocenters by using inexpensive D2O as a deuterium source further underscores the broad applicability and promising utility of this strategy. Moreover, mechanistic studies have provided clear insights into its challenges in terms of reactivity and enantioselectivity. The exploration will robustly inspire the development of thermodynamically unfavorable asymmetric olefin isomerizations.

Enantioselective Chemodivergent Three-Component Radical Tandem Reactions through Asymmetric Photoredox Catalysis.

Chemodivergent synthesis has been achieved in asymmetric photocatalysis. Under a dual catalyst system consisting of a chiral phosphoric acid and DPZ as a photosensitizer, different inorganic bases enabled the formation of two sets of valuable products from the three-component radical tandem transformations of 2-bromo-1-arylenthan-1-ones, styrenes, and quinoxalin-2(1H)-ones. The key to success was the distinct pKa environment, in which the radicals that formed on the quinoxalin-2(1H)-one rings after two radical addition processes underwent either single-electron oxidation or single-electron reduction. In addition, this work represents the first use of quinoxalin-2(1H)-ones in asymmetric photoredox catalysis.

Catalytic Asymmetric Intermolecular [3 + 2] Photocycloaddition of Cyclopropylamines with Electron-Deficient Olefins.

An enantioselective intermolecular [3 + 2] cycloaddition of N-arylcyclopropylamines with 2-aryl acrylates/ketones and cyclic ketone-derived terminal olefins via asymmetric photoredox catalysis is reported. A dual catalyst system involving DPZ and a chiral phosphoric acid is effective for the transformations, leading to a wide array of valuable cyclopentylamines with high yields, ee's, and drs. Among them, elaborate modulation of the ester group of 2-aryl acrylates was shown to be effective in improving reactivity, thereby enabling the success of the transformations.

Catalytic Asymmetric Hydrophosphinylation of 2-Vinylazaarenes to Access P-Chiral 2-Azaaryl-Ethylphosphine Oxides.

A chiral Brønsted acid-catalysed asymmetric hydrophosphinylation of 2-vinylazaarenes by secondary phosphine oxides is described. A variety of P-chiral 2-azaaryl-ethylphosphine oxides are synthesized with high yields and ees, of which both the substituents of phosphines and azaarenes can be flexibly modulated, underscoring an exceptionally broad scope of substrates. These adducts are valuable to asymmetric metal catalysis since the resultant P-chiral tertiary phosphines from the reduction of them are verified as a kind of effective C1 -symmetric chiral 1,5-hybrid P,N-ligands. Importantly, this catalysis platform enables the generic and efficient kinetic resolution of P-chiral secondary phosphine oxides. It thus provides an expedient approach to access the enantiomers of the P-chiral tertiary phosphine oxides derived from asymmetric hydrophosphinylation, further improving the utility of the method.

Kinetic Resolution of Azaarylethynyl Tertiary Alcohols by Chiral Brønsted Acid Catalysed Phosphine-Mediated Deoxygenation.

A chiral Brønsted acid catalysed phosphine-mediated deoxygenation protocol is reported. This metal-free method provides a precise kinetic resolution platform for azaarylethynyl tertiary alcohols, which are a broad category of biologically and synthetically important azaarene derivatives. In addition to providing an efficient method for the first asymmetric preparation of these tertiary alcohols, the strategy facilitates the construction of azaaryl-functionalized allenes with good to excellent enantioselectivities. The high selectivity factors (s up to 235), broad substrate scope, and ability to convert azaaryl compounds into both chiral tertiary alcohols and allenes robustly underscore the efficiency and promising utility of this method. The practicability is further validated by the successful synthesis of deuterated allenes with high ee values and substantial incorporation of deuterium using inexpensive D2 O as the deuterium source.

Deracemization through Sequential Photoredox-Neutral and Chiral Brønsted Acid Catalysis.

Catalytic deracemization is an ideal synthetic strategy due to its formally perfect atom utilization. Asymmetric photocatalysis has been appreciated as a promising tool to accomplish this attractive reaction pattern in an economical fashion, but it remains underdeveloped. Here, we report a new platform based on photoredox-neutral catalysis, allowing efficient and modular optical enrichment of α-amino esters and other valuable analogues. Two single-electron transfer processes between the photocatalyst and the substrates serve to provide the key prochiral intermediates, and the chiral Brønsted acid catalyst mediates enantioselective protonation to reconstitute a stereogenic C-H bond. The efficiency of deracemization is determined by the enantiofacial differentiation effect during the stereocentre-forming step.

Catalytic Enantioselective Reductive Cross Coupling of Electron-Deficient Olefins.

We report an enantioselective reductive cross coupling of electron-deficient olefins. Using a visible-light-driven cooperative photoredox and chiral Brønsted acid-catalyzed reaction with a Hantzsch ester as the terminal reductant, various cyclic and acyclic enones with 2-vinylpyridines were converted in high yields (up to 93%) to a wide range of enantioenriched pyridine derivatives featuring diverse γ-tertiary carbon stereocenters with good to excellent enantioselectivities (up to >99% ee).

Asymmetric Hydroaminoalkylation of Alkenylazaarenes via Cooperative Photoredox and Chiral Hydrogen-Bonding Catalysis.

Chiral hydrogen-bonding (H-bonding) catalytic asymmetric conjugate addition to activated olefins has been widely used to access enantioenriched molecules containing stereocenters at the ß-position of the olefin activating groups. Herein, we report the first highly enantioselective radical-based manifold. Under a dual organocatalyst system involving a chiral phosphoric acid and DPZ as the photoredox sensitizer, transformations of N-arylglycines, in which aryls with CF3 substituents are introduced, with alkenyl azaarenes afforded valuable hydroaminoalkylation adducts with satisfactory results. In addition to the diversity of azaarenes, the method can be used to construct aryl-, alkyl- and silyl-substituted stereocenter. Control experiments and density functional theory calculations were performed to elucidate a plausible reaction mechanism and the origin of stereoselectivity, wherein nonclassical H-bonding interactions were found to assist chiral catalysts in offering sufficient enantiocontrol.

All-Carbon Quaternary Stereocenters α to Azaarenes via Radical-Based Asymmetric Olefin Difunctionalization.

A radical-based asymmetric olefin difunctionalization strategy for rapidly forging all-carbon quaternary stereocenters α to diverse azaarenes is reported. Under cooperative photoredox and chiral Brønsted acid catalysis, cyclopropylamines with α-branched 2-vinylazaarenes can undergo a sequential two-step radical process, furnishing various valuable chiral azaarene-substituted cyclopentanes. The use of the rigid and confined C2-symmetric imidodiphosphoric acid catalysts achieves high enantio- and diastereo-selectivities for these asymmetric [3 + 2] cycloadditions.

Nonpassivated Silicon Anode Surface.

A stable solid electrolyte interphase (SEI) has been proven to be a key enabler to most advanced battery chemistries, where the reactivity between the electrolyte and the anode operating beyond the electrolyte stability limits must be kinetically suppressed by such SEIs. The graphite anode used in state-of-the-art Li-ion batteries presents the most representative SEI example. Because of similar operation potentials between graphite and silicon (Si), a similar passivation mechanism has been thought to apply on the Si anode when using the same carbonate-based electrolytes. In this work, we found that the chemical formation process of a proto-SEI on Si is closely entangled with incessant SEI decomposition, detachment, and reparation, which lead to continuous lithium consumption. Using a special galvanostatic protocol designed to observe the SEI formation prior to Si lithiation, we were able to deconvolute the electrochemical formation of such dynamic SEI from the morphology and mechanical complexities of Si and showed that a pristine Si anode could not be fully passivated in carbonate-based electrolytes.

Photoredox-catalysed formal [3+2] cycloaddition of N-aryl α-amino acids with isoquinoline N-oxides.

A formal [3+2] cycloaddition of N-aryl α-amino acids with isoquinoline N-oxides via visible light-driven photoredox catalysis is reported. Under transition metal-free conditions using a dicyanopyrazine-derived chromophore (DPZ) as the photoredox catalyst, the transformation was efficient and led to a series of important diazabicyclo[3.2.1]octane-based N-heterocyclic compounds. This work demonstrates the synthetic utility of N-aryl α-amino acids as 1,2-synthons and provides a new strategy for the dearomatization of isoquinolines.

Enantioselective reduction of azaarene-based ketones via visible light-driven photoredox asymmetric catalysis.

An enantioselective reduction of azaarene-based ketones through photoredox asymmetric catalysis is reported. With a transition metal-free dual catalytic system including a chiral phosphoric acid and a photosensitizer DPZ mediated by visible light, the transformations involved a tandem process involving double single-electron-transfer reductions and enantioselective protonation, providing valuable chiral alcohols in high yields (up to >99%) with good to excellent enantioselectivities (up to 97% ee).

Chiral acid-catalysed enantioselective C-H functionalization of toluene and its derivatives driven by visible light.

Toluene and its derivatives are petroleum-derived raw materials produced from gasoline by catalytic reformation. These abundant chemical feedstocks are commonly used as solvents in organic synthesis. The C(sp3)-H functionalization of these unactivated substrates has been widely used to directly introduce benzylic motifs into diverse molecules to furnish important compounds. Despite these advances, progress in asymmetric catalysis remains underdeveloped. Here, we report photoinduced radical-based enantioselective C(sp3)-C(sp3) coupling reactions of activated ketones with toluene and its derivatives by means of chiral acid catalysis. With a La(OTf)3/pybox complex catalyst, a variety of chiral 3-hydroxy-3-benzyl-substituted 2-oxindoles, including many conventionally difficult-to-access variants, are obtained directly from isatins in high yields with good to excellent enantioselectivities. Acenaphthoquinone is also compatible with the use of a chiral phosphoric acid (CPA) catalyst, leading to another series of important enantioenriched tertiary alcohols.

A rapid microwave-assisted phosphoric-acid treatment on carbon fiber surface for enhanced cell immobilization in xylitol fermentation.

A rapid microwave-assisted phosphoric-acid treatment (MP) was applied to modify the surface of carbon fibers (CFs) for cell immobilization and fermentation. After the novel treatment, the surface of CFs subjected to MP (CF-MP) contained the CPO and COP bonds and the surface area and hydrophilicity were enhanced, which improved the cell adhesion and growth compared with the raw CF. Because of these structural advantages, the biocompatibilities of the CF-MP as a cell carrier were improved according to the immobilization behavior of microorganisms and batch fermentation. The optimized immobilization efficiency of Candida tropicalis on the CF-MP was improved to 0.587 g g-1, and the maximum xylitol yield and volumetric productivity were 67.15% and 1.16 g h-1 L-1, respectively, which were substantially higher than that in case of the untreated CF. This indicated that the biocompatibility of CF improved after the favorable MP surface treatment, resulting in the enhancement of immobilized efficiency and xylitol fermentation.

Organocatalytic Asymmetric Cascade Aerobic Oxidation and Semipinacol Rearrangement Reaction: A Visible Light-Induced Approach to Access Chiral 2,2-Disubstituted Indolin-3-ones.

An enantioselective cascade aerobic oxidation and semipinacol rearrangement reaction of 2-aryl-3-alkyl-substituted indoles via visible-light-driven cooperative organophotoredox and H-bonding catalysis is reported. The current method provides an expedient and sustainable approach to furnish a variety of valuable chiral 2-aryl-2-alkyl-substituted indolin-3-ones in 64-90 % yield with 58-94 % ee. Preliminary control experiments present important insights into the stereochemistry.

Efficient removal of cadmium from soil-washing effluents by garlic peel biosorbent.

Paddy field soil contaminated by cadmium may produce cadmium-contained corns causing Itai-itai disease, and in situ washing of soil with the organic acid is a good technical choice due to its convenience and cost-effectiveness. While the bottleneck of this technique is how to recycle the huge volume of washing effluent in an efficient and economical way. Biosorption of cadmium on the garlic peel was attempted in present study and it was found quite satisfactorily effective to remove all cadmium from the real soil leaching effluent after three-time sequential adsorption. The systematical investigation on the effect of various parameters on the adsorption of cadmium on garlic peel in the existence of tartaric ligand was performed and it was found that tartrate could change Cd2+ into Cd(tar)0 species whose electrical charge state would restrain its approach to the adsorbent particles. The porous microstructure in the transversal surface of garlic peel and the abundant groups of -COOH are the main factors affecting the adsorption capability. A demonstrative flowsheet of soil remediation by chemical washing coupled with biosorption was proposed correspondingly, in which the cadmium could be recovered from the soil washing effluent, and the recovered effluent was reused for next soil washing, and recovered garlic peel was reused for cadmium adsorption from the effluents again, showing a great prospect in the remediation of paddy field soil contaminated by cadmium. Garlic peel was used to remove the cadmium from the soil washing effluent.