Ruthenium and Iodine Anion Cocatalyzed Cascade Dihalogenation and Cyclization of Internal Alkyne-Tethered Cyclohexadienones with 1,2-Dihaloethanes.

We have established an efficient ruthenium(II) and iodine anion cocatalyzed dihalogenation and cascade cyclization of internal alkyne-tethered cyclohexadienones, which stereoselectively afforded numerous dihalogenation products with a bioactive hydrobenzofuran skeleton in high yields under mild conditions. In this transformation, the reaction pathway was determined by the concentration of electrophilic iodine reagent, which also provided a strategy for control of the reaction selectivity. Furthermore, this method features the use of 1,2-dihaloroethane as the halogen source via iodine anion catalyst.

Phosphine-Catalyzed [3+2] Annulation of Hepta-2,3,5-trienedioates with Alkenes for the Construction of Exocyclic Olefinic Cyclopentenes.

Hepta-2,3,5-trienedioates 1 have been employed as substrates to explore Lewis base-catalyzed annulation reactions. This leads to the discovery of a phosphine-catalyzed [3+2] annulation of 1 with electron-deficient alkenes for the construction of exocyclic olefinic cyclopentenes in good yields and moderate E:Z ratios under mild conditions. The annulation is believed to proceed in a tandem [3+2] cyclization and double bond migration in which the ε-ester is crucial to both processes. This reaction also showcases a substrate-controlled divergent reactivity compared to that of a previous report.

Iodine Anion Catalyzed Cross-Dehydrogenative Aromatization for Access to Aromatic Amines.

A highly efficient iodine anion catalyzed cross-dehydrogenative aromatization of cyclohexenones with amines has been developed under metal-free conditions, which affords aromatic amines in good to excellent yields with a broad substrate scope. Meanwhile, this reaction provides a new method for the construction of C(sp2)-N bonds and also a new strategy for slow generation of oxidants or electrophiles via in situ dehalogenation. Moreover, this protocol affords a rapid and concise approach to chiral NOBIN derivatives.

Phosphine-Catalyzed Stereoselective Ring-Opening Addition of Cyclopropenones with Nucleophiles.

A phosphine-catalyzed ring-opening addition reaction of cyclopropenones with a variety of nucleophiles (NuH), including oxygen-, nitrogen-, sulfur-, and carbon-based ones, has been investigated, which produces potentially useful α,ß-unsaturated carbonyl derivatives in high yields (up to 99%), high regioselectivity, and exclusive E-selectivity. The reaction proceeds in high efficiency under very mild conditions using only 1 mol % PPh3 as the catalyst at room temperature. The method is also amenable for the synthesis of deuterated alkenes when deuterated nucleophiles (NuD) are employed. The mechanism is investigated by experiments and DFT calculations, which suggests an α-ketenyl phosphorus ylide as a key intermediate in the catalytic cycle that captures the nucleophiles in a stereoselective manner.

DABCO-Catalyzed [4 + 2] Annulation of 5-Methylenehex-2-ynedioates with Electron-Deficient Alkenes.

Herein, we describe a DABCO-catalyzed [4 + 2] annulation between 5-methylenehex-2-ynedioates and electron-deficient olefins to afford functionalized cyclohexadienes in good yields under mild conditions. The use of ß- and ε-carbons of the substrates for C-C bond formation is distinct from previous reports showing a substrate-controlled divergent reactivity. The annulation is believed to proceed in domino cyclization initiated by a cross Rauhut-Currier reaction.

Catalyst-Free [3 + 3] Annulation/Oxidation of Cyclic Amidines with Activated Olefins: When the Substrate Olefin Is Also an Oxidant.

Herein we describe a catalyst-free regioselective [3 + 3] annulation/oxidation reaction of cyclic amidines such as DBU (1,8-diazabicyclo(5.4.0)undec-7-ene) and DBN (1,5-diazabicyclo(4.3.0)non-5-ene) with activated olefins, i.e., 2-arylidenemalononitriles and 2-cyano-3-aryl acrylates, to afford tricyclic 2-pyridones and pyridin-2(1H)-imines, respectively. The mechanism has been proposed based on DFT calculations. In the reaction, the cyclic amidines serve as C,N-bisnucleophiles for the cyclization, while the olefins play a dual role by acting as both reactants and oxidants.

Magnetic imprinted nanoparticles with synergistic tailoring of covalent and non-covalent interactions for purification and detection of procyanidin B2.

A synergistic imprinting strategy of covalent and non-covalent interactions is proposed to prepare magnetic molecularly imprinted polymers (DI-MMIPs) for highly selective separation of procyanidin B2 (PC) from grape seed samples. Dopamine and 3-amino-phenylboronic acid as cooperative functional monomers endow the imprinted sites with synergistic tailoring. Benefiting from the synergistic effect, the DI-MMIPs exhibit enhanced imprinting performance with high adsorption capacity (27.71 mg g-1), fast kinetic equilibrium time (within 30 min), outstanding selectivity (IF = 5.8, SC > 3.2), and satisfactory regeneration ability. In addition, the DI-MMIPs possess good magnetism, uniform morphology with typical core-shell structure, and stable crystallization. Furthermore, the established DI-MMIPs coupled with HPLC-UV (~ 280 nm) method has a wide linearity range of 0.05-200 µg mL-1 with correlation coefficient of 0.9997, high recoveries (> 93.1%) with RSDs from 2.9 to 5.5%, and low LOD (0.0008 µg mL-1). Consequently, this work provides an effective and easily tailored way to fabricate magnetic imprinted nanomaterials with both rapid recognition rate and high selectivity and thus holds great promise to realize the extraction and detection of PC from real samples.

Synthesis of multiple-color emissive carbon dots towards white-light emission.

Multiple-color emissive carbon dots (C-dots) are gaining increasing attention in various fields. Herein, we report a facile solvothermal method for the synthesis of multiple-color emissive C-dots with the aim of white-light emission. Under single ultraviolet-light excitation, three C-dots emit a easily controlled fluorescent emission wavelength at 440 nm, 500 nm and 610 nm by using different three amines (either ammonium hydroxide, ethylenediamine or p-phenylenediamine, respectively) and pyromellitic dianhydride as molecular precursors while another three C-dots emit a controllable fluorescent emission wavelength at 500 nm, 550 nm and 585 nm by using same three amines and naphthalene-1,4,5,8-tetracarboxylic dianhydride as molecular precursors. The maximum fluorescence wavelength of these C-dots is red-shifted by changing three different amines molecular precursors from ammonium hydroxide, ethylenediamine, to p-phenylenediamine. Furthermore, these C-dots have shown promising applications in the fields of white-light-emitting diodes devices and color printing.

Redox-Neutral Annulation of Alkynylcyclopropanes with N-Aryloxyamides via Rhodium(III)-Catalyzed Sequential C-H/C-C Activation.

Alkynylcyclopropanes have been used for the first time as coupling partners in transition-metal-catalyzed C-H functionalization. Specifically, a Cp*RhIII-catalyzed regioselective annulation of alkynylcyclopropanes with N-aryloxyamides via redox-neutral C-H/C-C activation has been developed, which affords highly functionalized 2,3-dihydrobenzofurans bearing an ( E)-exocyclic carbon-carbon double bond and a tetra-substituted carbon center in moderate to good yields with a broad substrate scope.

Phosphine-Catalyzed Activation of Alkylidenecyclopropanes: Rearrangement to Form Polysubstituted Furans and Dienones.

We report a phosphine-catalyzed ring opening of electron-deficient alkylidenecyclopropanes (ACPs) to generate allylic phosphonium zwitterions that resemble the well-studied phosphine-allene adducts but exhibit distinct properties. The potent reactivity of these intermediates has been demonstrated in three types of substrate-controlled phosphine-catalyzed rearrangements of alkylidenecyclopropylketones, which chemoselectively afford tri- and tetrasubstituted furans, and trisubstituted dienones in good yields.

Rhodium(III)-Catalyzed Redox-Neutral C-H Activation/Annulation of N-Aryloxyacetamides with Alkynyloxiranes: Synthesis of Highly Functionalized 2,3-Dihydrobenzofurans.

Alkynyloxiranes have been employed for the first time as effective coupling partners in Cp*RhIII-catalyzed C-H functionalization reactions. Their annulation with N-aryloxyamides then offers a redox-neutral and efficient synthesis of functionalized 2,3-dihydrobenzofurans bearing an exocyclic E-allylic alcohol and a tetrasubstituted carbon center in good yields with a broad substrate scope. The products can be easily converted to molecules with more complexity, which provides an opportunity for rapid assembly of structurally diverse heterocycles.

Phosphine-Catalyzed Activation of Vinylcyclopropanes: Rearrangement of Vinylcyclopropylketones to Cycloheptenones.

We report a phosphine-catalyzed activation of electron-deficient vinylcyclopropanes (VCPs) to generate an ambident C5 synthon that is poised to undergo consecutive reactions. The utility of the activation is demonstrated in a phosphine-catalyzed rearrangement of vinylcyclopropylketones to cycloheptenones in good yields with a broad substrate scope. Mechanistic investigations support a stepwise process comprising homoconjugate addition, water-assisted proton transfer, and 7-endo-trig SN 2' ring closure.

Rhodium(III)-Catalyzed Annulative Carbooxygenation of 1,1-Disubstituted Alkenes Triggered by C-H Activation.

A Cp*RhIII -catalyzed annulative carbooxygenation of challenging 1,1-disubstituted alkenes triggered by C-H activation of N-aryloxyacetamides has been established, which affords 2,3-dihydrobenzofuran derivatives with a quaternary carbon center in good to excellent yields under mild redox-neutral conditions. An amide group on the alkenes is essential for the process, and may inhibit the ß-H elimination from C(sp3)-Rh species by saturating the rhodium center through coordination. Furthermore, mechanistic insights obtained from control experiments suggest a mechanism involving a RhIII -RhV -RhIII catalytic cycle.

Surface-rough Fe-N/C composite wrapped on carbon nanotubes as efficient electrocatalyst for oxygen reduction reaction.

Fe-N/C composites are considered one of the most promising non-precious-metal electrocatalysts for oxygen reduction reaction (ORR). In this paper, we fabricate a novel and efficient carbon nanotube (CNT)-supported Fe-N/C composite catalyst, via the surface-self-polymerization of polydopamine and then the incorporation with Fe species on CNTs, followed by the pyrolysis process. The obtained catalyst demonstrates excellent electrocatalytic performance towards ORR in alkaline media. The modification of Fe-incorporated nitrogen-rich-carbons (Fe-CNx) on CNTs lowers the ORR half-wave-potential by ∼190 mV, giving this catalyst with an onset ORR potential of 0.95 V (versus reversible hydrogen electrode (RHE)), a half-wave potential of 0.82 V (versus RHE), and the limiting current density of 5.39 mA cm-2 in 0.1 M KOH. The performance of the as-prepared catalyst is comparatively better than the commercially available Pt/C in terms of positive half-wave potential and larger limiting current, superior durability, and higher tolerance to the methanol.

DPPH·-luminol chemiluminescence system and its application in the determination of scutellarin in pharmaceutical injections and rat plasma with flow injection analysis.

In this article, a DPPH·-luminol chemiluminescence (CL) system was reported and the CL mechanism was discussed according to the CL kinetic properties after sequence injecting DPPH· into the DPPH·-luminol reaction mixture. It was observed that scutellarin could inhibit the CL response of the DPPH·-luminol system. Based on this observation, a simple and rapid flow injection CL method was developed for the determination of scutellarin using the inhibition effect in alkaline medium. The optimized chemical conditions for the CL reaction were 5 × 10-6  mol/L DPPH· and 1.0 × 10-4  mol/L luminol in 0.01 mol/L NaOH. Under optimized conditions, the CL intensity was inversely proportional to the concentration of scutellarin over the ranges 5-2000 and 40-3200 ng/ml in pharmaceutical injection and rat plasma, respectively. The limits of detection (S/N = 3) were 5 and 40 ng/ml in preparations and rat plasma, respectively. Furthermore, the precision, recovery and stability of the validated method were acceptable for the determination of scutellarin in both pharmaceutical injections and rat plasma. The presented method was successfully applied in the determination of scutellarin in pharmaceutical injections and real rat plasma samples.

Preparation and application of magnetic molecularly imprinted nanoparticles for the selective extraction of osthole in Libanotis Buchtomensis herbal extract.

In this work, novel magnetic molecularly imprinted polymers were prepared for the selective extraction of osthole from Libanotis Buchtomensis herbal extract. During the synthesis process, double bonds grafted on the surface of Fe3 O4 nanoparticles could not only drive the temple molecules to locate onto the surface of vinyl-functionalized magnetic nanoparticles by π-π conjugation, which makes the distribution of binding sites ordered, but also direct the occurrence of imprinting polymerization at the surface of magnetic nanoparticles by the copolymerization of vinyl terminal groups with functional monomers and cross-linking agent. The characteristics of the resulting polymers were evaluated by transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and vibrating sample magnetometry. Adsorption kinetics, isotherms, selectivity, reproducibility, and reusability were discussed, which suggest that the obtained nanomaterials possess rapid binding kinetics, high adsorption capacity of 17.65 mg/g, and favorable selectivity for the target molecule. Satisfactory reproducibility and reusability were verified as well. Meanwhile, the resultant imprinted nanoparticles were successfully applied to selectively separate osthole from the herbal extract, which show great potential in extracting active ingredients from traditional Chinese medicine.

Selective adsorption of protein by a high-efficiency Cu(2+) -cooperated magnetic imprinted nanomaterial.

We report a core-shell magnetic molecularly imprinted polymer with high affinity through a facile sol-gel method for the selective adsorption of bovine hemoglobin from real bovine blood. Copper ions grafted on the surface of the matrix could immobilize template protein through chelation, which greatly enhances the orderliness of imprinted cavities and affinity of polymers. The obtained products exhibit a desired level of magnetic susceptibility, resulting in the highly efficient adsorption process. The results of adsorption experiments show that the saturation adsorption capacity of imprinted products could reach 116.3 mg/g within 30 min. Meanwhile, the specific binding experiment demonstrates the high selectivity of polymers for bovine hemoglobin. Furthermore, satisfactory reusability is demonstrated by ten adsorption-desorption cycles with no obvious deterioration in binding capacity. Electrophoretic analysis suggests the polymer could be used successfully in separation and enrichment of bovine hemoglobin from the bovine blood sample, which exhibits potential application in pretreatment of proteomics.

Preparation of magnetic glycoprotein-imprinted nanoparticles with dendritic polyethyleneimine as a monomer for the specific recognition of ovalbumin from egg white.

Glycoproteins are crucial in massive physiological events and clinical application. It is necessary to prepare new materials to isolate the specific glycoprotein. New and simple core-shell molecularly imprinted polymers were prepared by surface imprinting. The polymers are synthesized with magnetic nanoparticles as the core, water-soluble dendritic polyethyleneimine as the monomer and the ovalbumin as the template. The prepared imprinted polymers showed thin imprinted shell, biocompatibility and superparamagnetic properties. The resultant materials exhibited fast kinetics, high adsorption capacity, perfect selectivity and reusability. More important, they can absorb the template glycoprotein from the neutral solution and successfully be applied to recognize the ovalbumin from egg white, which means that they can provide an alternate method to isolate glycoprotein from bodily fluids.

A chemiluminescence method to detect hydroquinone with water-soluble sulphonato-(salen)manganese(III) complex as catalyst.

A water-soluble sulphonato-(salen)manganese(III) complex with excellent catalytic properties was synthesized and demonstrated to greatly enhance the chemiluminescence signal of the hydrogen peroxide - luminol reaction. Coupled with flow-injection technique, a simple and sensitive chemiluminescence method was first developed to detect hydroquinone based on the chemiluminescence system of the hydrogen peroxide-luminol-sulphonato-(salen)manganese(III) complex. Under optimal conditions, the assay exhibited a wide linear range from 0.1 to 10 ng mL(-1) with a detection limit of 0.05 ng mL(-1) for hydroquinone. The method was applied successfully to detect hydroquinone in tap-water and mineral-water, with a sampling frequency of 120 times per hour. The relative standard deviation for determination of hydroquinone was less than 5.6%, and the recoveries ranged from 96.8 to 103.0%. The ultraviolet spectra, chemiluminescence spectra, and the reaction kinetics for the peroxide-luminol-sulphonato-(salen)manganese(III) complex system were employed to study the possible chemiluminescence mechanism. The proposed chemiluminescence analysis technique is rapid and sensitive, with low cost, and could be easily extended and applied to other compounds.

Construction of dispirocyclohexanes via amine-catalyzed [2 + 2 + 2] annulations of Morita-Baylis-Hillman acetates with exocyclic alkenes.

Amine-catalyzed [2 + 2 + 2] annulations of one molecule of Morita-Baylis-Hillman (MBH) acetates 1 with two molecules of 2-(arylmethylidene)indane-1,3-diones 2 or methyleneindolinones 4 have been developed under very mild conditions, which produce multistereogenic dispirocyclohexanes 3 and 5, respectively, in moderate to excellent yields and good diastereoselectivity. This amine-catalyzed annulation constitutes a novel and efficient method for the construction of dispirocyclohexane motifs, and also showcases the divergent catalysis between amines and phosphines with regard to the corresponding phosphine-catalyzed [3 + 2] annulations.