Organocatalytic Enantioselective Synthesis of Inherently Chiral Calix[4]arenes.

Inherently chiral calix[4]arenes are an excellent structural scaffold for enantioselective synthesis, chiral recognition, sensing, and circularly polarized luminescence. However, their catalytic enantioselective synthesis remains challenging. Herein, we report an efficient synthesis of inherently chiral calix[4]arene derivatives via cascade enantioselective cyclization and oxidation reactions.

Palladium-catalyzed asymmetric carbene coupling en route to inherently chiral heptagon-containing polyarenes.

Developing facile and direct synthesis routes for enantioselective construction of cyclic π-conjugated molecules is crucial. However, originate chirality from the distorted structure around heptagon-containing polyarenes is largely overlooked, the enantioselective construction of all-carbon heptagon-containing polyarenes remains a challenge. Herein, we present a highly enantioselective synthesis route for fabricating all carbon heptagon-containing polyarenes via palladium-catalyzed carbene-based cross-coupling of benzyl bromides and N-arylsulfonylhydrazones.

Enantioselective Nickel-Catalyzed Denitrogenative Transannulation En Route to N-N Atropisomers.

Nickel-catalyzed transannulation reactions triggered by the extrusion of small gaseous molecules have emerged as a powerful strategy for the efficient construction of heterocyclic compounds. However, their use in asymmetric synthesis remains challenging because of the difficulty in controlling stereo- and regioselectivity. Herein, we report the first nickel-catalyzed asymmetric synthesis of N-N atropisomers by the denitrogenative transannulation of benzotriazones with alkynes.

Organocatalytic Enantioselective Synthesis of Seven-Membered Ring with Inherent Chirality.

Inherent chirality is used to describe chiral cyclic molecules devoid of central, axial, planar, or helical chirality and has tremendous applications in chiral recognition and enantioselective synthesis. Catalytic and divergent syntheses of inherently chiral molecules have attracted increasing interest from chemists. Herein, we report the enantioselective synthesis of inherently chiral tribenzocycloheptene derivatives via chiral phosphoric acid (CPA)-catalyzed condensation of cyclic ketones and hydroxylamines.

Fabrication of two novel amino-functionalized and starch-coated CuFeO-modified magnetic biochar composites and their application in removing Pb and Cd from wastewater.

Novel magnetic biochar composites (SFeCu@SBCO and FeCu@SBCO-NH) were fabricated by modifying oxidized sawdust biochar (SBCO) with Fe/Cu loading, starch-coating/amination, characterized (FTIR, XRD, BET, SEM-EDS and XPS) and applied in capturing Pb and Cd from wastewater. Adsorption experiments revealed that SFeCu@SBCO and FeCu@SBCO-NH exhibited extraordinary adsorption performance toward Pb/Cd with the maximum adsorption capacity reaching 184.26/173.

Screening of Deoxynivalenol Cyclic Heptapeptide Mimotope Antigen.

In this study, phage clones that can bind to DON were selected from the phage cyclohepta peptide library by screening through the principle of solid-phase affinity, and mimotope were synthesized to replace the DON toxin standard to establish a green low toxicity detection system. The author conducted four rounds of screening in the phage cyclic heptapeptide library with DON-10a1a monoclonal antibody as the target molecule. Then 38 phage clones were selected and validated, and the results showed that 35 of them could bind to the DON-10a1a monoclonal antibody and were inhibited by DON toxin.

Catalytic Asymmetric Synthesis of N-N Biaryl Atropisomers.

Atropisomers have emerged as important structural scaffolds in natural products, drug design, and asymmetric synthesis. Recently, N-N biaryl atropisomers have drawn increasing interest due to their unique structure and relatively stable axes. However, its asymmetric synthesis remains scarce compared to its well-developed C-C biaryl analogs.

Atroposelective Synthesis of C-N Vinylindole Atropisomers by Palladium-Catalyzed Asymmetric Hydroarylation of 1-Alkynylindoles.

Transition-metal-catalyzed hydroarylation of unsymmetrical internal alkynes remains challenging because of the difficulty in controlling regioselectivity and stereoselectivity. Moreover, the enantioselective hydroarylation of alkynes using organoboron reagents has not been reported. Herein, we report for the first time that palladium compounds can catalyze the hydroarylation of 1-alkynylindoles with organoborons for the synthesis of chiral C-N atropisomers.

Catalytic Asymmetric Synthesis of Atropisomers Featuring an Aza Axis.

ConspectusAtropisomers bearing a rotation-restricted axis are common structural units in natural products, chiral ligands, and drugs; thus, the prevalence of asymmetric synthesis has increased in recent decades. Research into atropisomers featuring an N-containing axis (N-X atropisomers) remains in its infancy compared with the well-developed C-C atropisomer analogue. Notably, N-X atropisomers could offer divergent scaffolds, which are extremely important in bioactive molecules.

Palladium-Catalyzed Double -Arylation to Access Unsymmetric ,'-Bicarbazole Scaffolds.

Herein, the palladium-catalyzed double C-N coupling of 9-carbazol-9-amines and 2,2'-dibromo-1,1'-biphenyl is reported. This protocol offers access to ,'-bicarbazole scaffolds, which have frequently been used as linkers in the construction of functional covalent organic frameworks (COFs). A variety of substituted ,'-bicarbazoles were synthesized in moderate to high yields based on this chemistry, and the potential application of this method was showcased by the synthesis of COF monomers like tetrabromide and tetraalkynylate .

Palladium-catalyzed enantioselective rearrangement of dienyl cyclopropanes.

Vinyl cyclopropanes (VCPs) are among the most useful three-carbon building blocks in organic synthesis. They are commonly used as dienophiles in a range of cycloaddition reactions. However, VCP rearrangement has not received much attention since its discovery in 1959.

Enantioselective Synthesis of N-N Atropisomers by Palladium-Catalyzed C-H Functionalization of Pyrroles.

The catalytic asymmetric construction of N-N atropisomeric biaryls remains a formidable challenge. Studies of them lag far behind studies of the more classical carbon-carbon biaryl atropisomers, hampering meaningful development. Herein, the first palladium-catalyzed enantioselective C-H activation of pyrroles for the synthesis of N-N atropisomers is presented.

The Asymmetric Buchwald-Hartwig Amination Reaction.

Over the past few decades, the Buchwald-Hartwig reaction has emerged as a powerful tool for forging C-N bonds, and has been vital to the pharmaceuticals, materials, and catalysis fields. However, asymmetric Buchwald-Hartwig amination reactions for constructing centered chirality, planar chirality, and axial chirality remain in their infancy owing to limited substrate scope and laggard ligand design. The recent surge in interest in the synthesis of C-N/N-N atropisomers, has witnessed a renaissance in asymmetric Buchwald-Hartwig amination chemistry as the first practical protocol for the preparation of C-N atropisomers.

Atroposelective Synthesis of N-Arylated Quinoids by Organocatalytic Tandem N-Arylation/Oxidation.

Diarylamines and related scaffolds are ubiquitous atropisomeric chemotypes in biologically active natural products. However, the catalytic asymmetric synthesis of these axially chiral compounds remains largely unexplored. Herein, we report that a BINOL-derived chiral phosphoric acid (CPA) successfully catalyzed the atroposelective coupling of quinone esters and anilines through direct C-N bond formation to afford N-aryl quinone atropisomers with an unprecedented intramolecular N-H-O hydrogen bond within a six-membered ring in good yields and enantioselectivities with the quinone ester as both the electrophile and the oxidant.

Enantioselective Synthesis of N-N Bisindole Atropisomers.

N-N Atropisomers are a common motif in natural products and represent a significant dimension for exploration in modern pharmaceutical and medicinal chemistry. However, the catalytic atroposelective synthesis of such molecules remains challenging, hampering meaningful development. In particular, an enantioselective synthesis of N-N bisindole atropisomers is unprecedented.

Palladium/Amino Acid Co-catalyzed Atroposelective C-H Olefination to Access Tetra-Ortho-Substituted Atropisomers Featuring 2,2'-Difluoro-1-biaryl Scaffolds.

Despite the great advancement in atroposelective synthesis in the past decades, the enantioselective synthesis of 2,2'-difluoro-1-biaryls is unprecedented. Herein, a palladium and chiral amino acid catalyzed atroposelective C-H olefination to construct the axially chiral 2,2'-difluoro-1-biaryls is reported. A variety of polyfluoro-substituted biaryls were forged under mild conditions in good yields with excellent enantioselectivity (up to 99% ee).

Synthesis and application of starch-stablized Fe-Mn/biochar composites for the removal of lead from water and soil.

Starch-stablized and Fe/Mn bimetals modified biochar derived from corn straw (SFM@CBC and SFM@CBC-350) were firstly prepared, characterized (FTIR, XRD, SEM, EDS, BET and XPS), and applied in Pb removal from water and soil. SFM@CBC and SFM@CBC-350 displayed highly effective adsorption performance of Pb from wastewater with the maximum adsorption capacity of 170.91 mg g and 190.

Cu(I)-Catalyzed Asymmetric Arylation of Pyrroles with Diaryliodonium Salts toward the Synthesis of N-N Atropisomers.

We report herein that copper(I) catalysis using a bis(phosphine) dioxide ligand can catalyze the desymmetric C-H arylation of prochiral bipyrroles. More than 50 nitrogen-nitrogen atropisomers were achieved in good to excellent yields with excellent enantioselectivities (≤97% yield, ≤98% ee). The reaction proceeds under mild conditions with good functional group compatibility on arenes and diaryliodonium salts.

Removal of U(vi) from aqueous solutions by an effective bio-adsorbent from walnut shell and cellulose composite-stabilized iron sulfide nanoparticles.

FeS nanoparticles were easily aggregated and oxidized in the natural environment. It was important to stabilize the iron sulfide nanoparticle composite with a stabilizer. Biochar could be used as an effective carrier to inhibit the agglomeration and oxidization of FeS nanoparticles.

Biochar-supported starch/chitosan-stabilized nano-iron sulfide composites for the removal of lead ions and nitrogen from aqueous solutions.

Novel materials that nano-FeS and starch (or chitosan) loaded on peanut shells biochar(Starch-FeS@PSB and Chitosan-FeS@PSB) were prepared and applied for removal of Pb(II) and nitrogen(NO-N and NH-N) in wastewater. It showed that Starch-FeS@PSB and Chitosan-FeS@PSB had excellent absorptive effects compared with PSB. The maximum adsorption capacity of Pb(II) by Starch-FeS@PSB and Chitosan-FeS@PSB reached 91.

Functionalized porous nanoscale FeO particles supported biochar from peanut shell for Pb(II) ions removal from landscape wastewater.

The large amounts ofheavy metal from landscape wastewater have become serious problems of environmental pollution and risks for human health. The development of efficient novel adsorbent is a very important for treatment of heavy metal. The functionalized porous nanoscale FeO particles supported biochar from peanut shell (PS-FeO) for removal of Pb(II) ions from aqueous solution was investigated.

High effective enrichment of U(VI) from aqueous solutions on versatile crystalline carbohydrate polymer-functionalized graphene oxide.

The removal of uranium on various sorbents has been widely employed in recent times. However, the limited sorption capacities of these sorbents inhibit the actual application of the radionuclide in actual environments. The development of a novel material with high sorption capacity and superior regeneration for the removal of uranium is highly desirable.

Improved Pb(II) removal in aqueous solution by sulfide@biochar and polysaccharose-FeS@ biochar composites: Efficiencies and mechanisms.

Novel biochars, namely nano iron sulfide@ walnut shell biochar (FeS@WNS), Starch-FeS@WNS and Chitosan-FeS@WNS, were prepared by WNS loaded with nano FeS and starch (or chitosan). Nano FeS can be effectively improved lead ions (Pb(II)) removal and starch (or chitosan) improved the stability of FeS and the defect of easy agglomeration. The materials were characterized by SEM, EDS, FTIR and XRD, and the preparation was successful.

Enantioselective Synthesis of Nitrogen-Nitrogen Biaryl Atropisomers via Copper-Catalyzed Friedel-Crafts Alkylation Reaction.

Nitrogen-nitrogen bonds containing motifs are ubiquitous in natural products and bioactive compounds. However, the atropisomerism arising from a restricted rotation around an N-N bond is largely overlooked. Here, we describe a method to access the first enantioselective synthesis of N-N biaryl atropisomers via a Cu-bisoxazoline-catalyzed Friedel-Crafts alkylation reaction.