An oxidative cyclization reaction based fluorescent “Turn-On” probe for highly selective and rapid detection of hypochlorous acid

A novel fluorescent turn-on probe, PHC1, for the detection of hypochlorous acid has been developed based on hypochlorous acid-initiated oxidative intramolecular cyclization. Endowed by the fast reaction rate, PHC1 features rapid detection kinetics, as well as high degree of selectivity and sensitivity for HClO.     

Enantioselective hydrogen atom transfer to α-sulfonyl radicals controlled by selective coordination of a chiral Lewis acid to an enantiotopic sulfonyl oxygen

Enantioselective hydrogen atom transfer to α-sulfonyl radicals generated from the alkyl radical addition to 2-propenyl and 1-phenylethenyl sulfones in the presence of chiral Lewis acids affords products with high enantioselectivity. The stereochemical course is discussed with the transition states involving selective coordination of a chiral Lewis acid to an enantiotopic sulfonyl oxygen.     

A highly selective and sensitive fluorescent chemosensor for Zn^2＋

A new selective Zn^2＋ fluorescent chemosensor, o-vanillin-4-ethoxybenzoylhydrazone （1）, was designed and prepared. Free 1 mainly displayed very weak fluorescence at 480 nm upon excitation at 403 nm. It displayed high selectivity for Zn^2＋ and had a 518- fold fluorescent enhancement upon binding of Zn^2＋, while the other cation ions had only little influence on the fluorescence of 1. Mechanism of enhancement of l＇s fluorescence by Zn^2＋ was briefly discussed.     

Efficient and stable tin-based perovskite solar cells by introducing π-conjugated Lewis base

Science China Chemistry - Tin-based perovskite solar cells (TPSCs) as the most promising candidate for lead-free PSCs have incurred extensive researches all over the world. However, the...     

Preparation and characterization of highly photoactive nanocrystalline TiO_2 powders by solvent evaporation- induced crystallization method

Highly photoactive bi-phase nanocrystalline TiO2 photocatalyst was prepared by a solvent evaporation-induced crystallization (SEIC) method, and calcined at different temperatures. The obtained TiO2 photocatalyst was characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM) and BET surface areas. The photocatalytic activity was evaluated by the photocatalytic oxidation of acetone in air. The results show that solvent evaporation can promote the crystallization and phase transformation of TiO2 at 100℃. When calcination temperatures are below 600℃, the prepared TiO2 powders show bimodal pore size distributions in the mesoporous region. At 700℃, the pore size distributions exhibit monomodal distribution of the inter-aggregated pores due to the collapse of the intra-aggregated pores. At 100℃, the obtained TiO2 photocatalyst by this method shows good photocatalytic activity, and at 400℃, its photocatalytic activity exceeds that of Degussa P25. This may be attributed to the fact t     

Chiral Lewis base-assisted Brønsted acid (LBBA)-catalyzed enantioselective cyclization of 2-geranylphenols

Chiral Lewis base-assisted Br?nsted acids (Chiral LBBAs) have been designed as new organocatalysts for biomimetic enantioselective cyclization. A salt of a chiral phosphonous acid diester with FSO(3)H catalyzes the enantioselective cyclization of 2-geranylphenols to give the desired trans-fused cyclized products with high diastereo- and enantioselectivities (up to 98:2 dr and 93% ee).     

A fluorescent Eu(Ⅲ) MOF for highly selective and sensitive sensing of picric acid

A metal-organic framework [Eu_3L_3(CH_3COO)_2(H_2O)_2(μ_3-OH)]·3 DMF,(EuL, H_2L=9H-carbazole-2,7-dicarboxylic acid,DMF=N,N-dimethylformamide) has been synthesized under solvothermal conditions and structurally characterized. In EuL,Eu_6O_8 clusters are four-bridged by carboxylates to form parallel-aligned Eu–O–C chains, which are further linked by the carbazole moieties of L~(2-) ligands to form the three-dimensional framework with rhombic channels. The EuL material with characteristic emission of Eu~(3+) ion exhibits significant luminescence quenching response for picric acid(PA) and the linear Stern-Volmer plot was observed in the concentration range of 0.05–0.15 mM with K_(sv) of 98074 M~(-1). As far as we know, this Ksv is among the highest values for COFs and MOFs in detection of PA. The excellent anti-interference ability and repeatability were also verified by experiments. Lastly, we investigated the luminescence quenching mechanism in the EuL sensing system.     

Novel and Efficient Approach to Fluorinated β‐Aminobutanones Catalyzed by Molecular Iodine

A variety of fluorinated compounds of β‐amino ketones could be obtained in good to excellent yields at room temperature through a three‐component Mannich reaction of aldehydes, anilines, and acetones catalyzed by iodine.     

Access to new sequiterpenoids by catalytic acid rearrangement of 9α-hydroxyparthenolide

The catalytic acid rearrangement of 9α-hydroxyparthenolide (1), the main constituent of Anvillea radiata, has been studied. Several new sesquiterpene compounds were obtained and their structures were fully elucidated. A mechanism to explain the formation of these compounds is proposed.     

Synthesis of substituted 2-hydrazino- and 2-(Β-acylhydrazino)-cinchoninic acid amides and their cyclization to 1,2,4-triazolo[4,3-a]quinoline-9-carboxylic acid amides

The reaction of substituted 2-chlorocinchoninic acid amides with hydrazine hydrate or acylhydrazines gave 2-hydrazino- and 2-(-acylhydrazino)cinchoninic acid amides. The latter were also obtained by acylation of the 2-hydrazino derivatives. It is shown that 1,2,4-triazolo[4,3-a]quinoline-9-carboxylic acid amides are formed when 2-hydrazinocinchoninic acid amides are refluxed with formic or acetic acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 493–496, April, 1991.     

Liquid-phase catalytic transfer hydrogenation and cyclization of levulinic acid and its esters to γ-valerolactone over metal oxide catalysts

Levulinic acid and its esters are converted to γ-valerolactone over metal oxide catalysts by catalytic transfer hydrogenation via the Meerwein-Ponndorf-Verley reaction.     

Sensitive and selective determination of glutathione in probiotic bacteria by capillary electrophoresis–laser induced fluorescence

Glutathione (GSH) is a thiol with an important function in protecting tissue against the oxidative stress which has been related to carcinogenesis in the colon. For this reason the development of probiotic species producing glutathione could be of great interest. To determine the glutathione content of some probiotic bacteria of the Bifidobacterium and Lactococcus genera, a very sensitive and selective analytical method based on capillary electrophoresis coupled to laser-induced fluorescence detection has been developed. Pretreatment of cell-lysate samples is very simple—precipitation of protein with acetonitrile in 1:2 volume ratio. The fluorophore 5-iodoacetamidofluorescein (5-IAF) was chosen for glutathione derivatisation; it reacts with thiols at pH 12.5, forming a fluorescent adduct which is excited by a laser at 488 nm for detection. The reaction conditions optimised were temperature, time, and 5-IAF/GSH molar ratio. Electrophoresis was performed with a carbonate buffer (25 mmol L⁻¹, pH 9.8) as background electrolyte and a voltage of 30 kV; an electrophoretic run was complete in less than 7 min. There was a good linear relationship between concentration and response in the range 2.5–500 ng mL⁻¹ and the LOD was 0.5 ng mL⁻¹. The glutathione content of probiotic cells was determined by using the standard additions method to reduce matrix effects. The method was fully validated and shown to be of suitable sensitivity and selectivity for determination of GSH in probiotic cell lysates.     

Efficient electrocatalytic oxidation and selective determination of isoniazid by Fe(tmphen) 3 2+ -exchanged Nafion?-modified electrode

Cyclic voltammetry and electrochemical impedance studies of Fe(tmphen) ₃ ²⁺ (where tmphen?=?3,4,7,8-tetramethyl-1,10-phenanthroline)-immobilized Nafion?-modified glassy carbon electrode (GC/Nf/Fe(tmphen) ₃ ²⁺ ) are carried out in 0.1?M Na₂SO₄ solution. Nafion–Fe(tmphen) ₃ ²⁺ complex exhibits efficient electrocatalytic oxidation of isoniazid. The linear double reciprocal plot of current and concentration of isoniazid shows a Michaelis–Menten-type catalytic process. The catalytic oxidation currents are proportional to the concentration of isoniazid and show a wide linear calibration range for the quantitative determination of isoniazid. Detection limit and sensitivity are found to be 13?μM and 2.5?μA?mM^?1, respectively.     

Regio- and π-facial selective Lewis acid interceded Diels-Alder reactions of α-dienyl-β-lactams: an indepth analysis

The regio-, diastereo-, and π-facial selective Lewis acid mediated Diels-Alder reactions of cis/trans-3-butadienyl-2-azetidinones with unsymmetrical dienophiles viz. methyl acrylate, dimethyl fumarate, and acrolein leading to the synthesis of diastereomerically pure and biologically potent 1,3,4-trisubstituted-2-azetidinones are reported. Theoretical calculations at HF/6-31G^∗∗ and 6-31G^∗∗/DFT levels have been performed to support the observed π-facial selectivity. The formation of diastereomerically pure ‘endo’ adducts is supported by the X-ray diffraction studies.     

Noncatalytic selective 6-O-acetylation of methyl 2,3-di-O-benzoyl-α-d-glucopyranoside with acetic acid and acetic anhydride

Russian Chemical Bulletin - Noncatalytic acetylation of methyl 2,3-di-O-benzoyl-α-d-glucopyranoside with acetic acid or acetic anhydride proceeds regioselectively at the primary hydroxyl group...     

1,4-Addition of silicon dienoates to α,β-unsaturated aldehydes catalyzed by in situ-generated silicon Lewis acid

In situ-generated silyl methide species (R(3)Si-CTf(2)R') effectively catalyzed the reaction of β-substituted α,β-unsaturated aldehydes with silicon dienoates such as 3-bromo-2-TESO-furan to give the corresponding γ-adducts with excellent 1,4-selectivity and good anti selectivity.     

Automatic assembly of skeleton structures. 3. Stereoselective synthesis,stereochemistry, and cyclization ofd,l-α,α'-dioxy-α,α'-di-tert-butylglutaric acid

Stereoselective synthesis of d,l-,-dioxy-,-di-tert-butylglutaric acid hydroxyiminolactonitrile (3) was conducted by the reaction of dipivaloylmethane with HCN in ether. The corresponding hydroxylacetonitrile (4) and amide (5), acid (6), and its ester (7), from which dilactone (8) was synthesized with preparative yields, were obtained from3. Benzyl amide (9) was obtained by the reaction of8 with BnNH₂. The iminolactone structure3 of dipivaloylmethane bis-cyanohyrin, thecis-pseudo-a orientation of the functional substituents in3–7 and9, and the structure of the dilactone8 were confirmed by the¹H,¹³C NMR,IR and mass spectra.For previous communication, see [2].N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1591–1601, July, 1992.     

Efficient synthesis of N-nosyl-protected 3-azabicyclo[4.3.0]nonen-8-one by an aniline- and nitrobenzene-mediated Pauson–Khand cyclization

The intramolecular Pauson–Khand cyclization in the presence of both aniline and nitrobenzene was used to improve the construction of N-nitrobenzenesulfonyl-protected 3-azabicyclo[4.3.0]nonane skeletons. We found that aniline enhanced the cyclization and that nitrobenzene prevents the concurrent reduction in this process. This combination of mediators allows for the efficient synthesis of bioactive azabicyclic nonane-type alkaloids and the use of milder deprotection conditions in the synthetic route.