Enantioselective total synthesis of (-)-kibdelone C

The kibdelones are aromatic polyketide natural products featuring isoquinolinone and tetrahydroxanthone ring systems. They display potent cytotoxicity toward a range of human cancer cell lines. Here, we present an enantioselective total synthesis of kibdelone C that utilizes a Shi epoxidation to establish the absolute and relative stereochemistry, an acid-catalyzed cyclization to form the tetrahydroxanthone, and a C-H arylation to complete the hexacyclic skeleton.     

Synthesis of 1‐Aryl‐1H‐indazoles via a Ligand‐Free Copper‐ Catalyzed Intramolecular Amination Reaction

A general synthesis of 1‐aryl‐1‐H‐indazoles from o‐halogenated aryl aldehydes or ketones and aryl hydrazines was described. This protocol included an intermolecular condensation and a ligand‐free copper‐catalyzed intramolecular Ullmann‐type coupling reaction. This method was applied to a wide range of substrates to produce the indazole products in good yields.     

ICP-AES法测定烟花爆竹中16种化学成分的不确定度评定

采用电感耦合等离子体-原子发射光谱(ICP-AES)法测定烟花爆竹中16种化学成分并对测定结果的不确定度进行了评定和计算,提供了评定过程所需的各参数的采集和计算方法,定量表征了测定结果的可信程度.由计算得到的合成标准不确定度可以看出,不确定度主要来源于校准曲线的非线性,从而对此测定方法的可行性和准确性进行了科学的判断.     

Metal-carboxylate coordination polymers with redox-active moiety of tetrathiafulvalene (TTF)

Though numerous metal-organic frameworks or polymers have been reported, the organic building blocks are usually not redox-active. On the other hand, some mono-, di- or tri-nuclear compounds with tetrathiafulvalene (TTF) have been prepared, although little is known about the coordination polymers combined with paramagnetic metals and organic TTF ligands. We report herein a series of coordination polymers of copper(II) and manganese(II) with TTF dicarboxylate ligand (L). Compound 1, [CuL(2,2-bpy)](n), is a one-dimensional (1-D) coordination polymer with five-coordinated square-pyramidal Cu(II) centers. Mn(II) complex 2, [MnL(2,2-bpy)](n), also takes a 1-D structure, showing a double-bridged mode by carboxylate groups. The 4,4-bipyridine compound 3, [MnL(4,4-bpy)(H(2)O)](n)·CH(3)CN, takes a 2-D grid network. A zinc(II) compound 4, [ZnL(4,4-bpy)(H(2)O)](n)·CH(3)CN, isomorphous structure with 3, is also presented. The electrochemical properties of the solid-state compounds were investigated by cyclic voltammetry using surface-modified electrodes. As usually observed in TTF derivatives, two sets of redox-waves were observed. The values of E(1/2)(1) of compounds 1-4 are in the order of 2(Mn) ≈ 3(Mn) < 1(Cu) < 4(Zn), indicating that the metal coordination can affect the potential shift of the TTF ligand. Weak antiferromagnetic exchanges are observed for compounds 1, 2, and 3.     

Coatings of one monomer molecularly imprinted polymers for open tubular capillary electrochromatography

One monomer molecularly imprinted polymer coatings were first synthesized in fused silica capillary columns with 2-methacrylamidopropyl methacrylate (MAM) as single functional monomer in addition to a cross-linking monomer. Since MAM may generate no or little EOF, a strategy of precursor of polymerization, which does not interfere with the formation of defined imprints, was used to introduce an ionizable functional monomer to generate a stable electroosmotic flow for electrochromatography (CEC) by post-polymerization hydrolization. The resulting MAM-based open-tubular imprinted capillary was able to separate enantiomers by means of CEC. The resolution of enantiomers separation achieved on S-amlodipine-imprinted capillary was up to 16.1. The strong recognition ability (selectivity factor was 3.23) and high column performance (theory plates was 26,053 plates m(-1)) of template were obtained. The MIP coatings were also prepared using either S-naproxen or S-ketoprofen as template molecule. The resolutions of enantiomers separation were 2.20 and 4.56, respectively. The results illustrate that the synthesis of MIP using one monomer is not only an experimental-simplified process, but also an approach to producing chiral stationary phase with high efficiency and selectivity.     

A mild liquid reduction route toward uniform blue-emitting EuCl2 nanoprisms and nanorods

In this work, for the first time, uniform blue-emitting EuCl(2) nanoprisms and nanorods were synthesized from Eu(CCl(3)COO)(3)·2H(2)O [or Eu(CH(3)COO)(3)·H(2)O] by a novel mild liquid reduction route, using acetamidine hydrochloride (or picolinamidine hydrochloride) as the reductant in oleylamine. The synthetic reaction even can take place under an atmosphere in the absence of inert gas at around 300 °C. The EuCl(2) nanoprism dispersion in n-hexane showed an intense blue emission when excited by UV light.     

Mapping molecular conformations with multiple-mode two-dimensional infrared spectroscopy

The multiple-mode two-dimensional infrared (2D-IR) spectrum in a broad frequency range from 1000 to 3200 cm(-1) of a 1-cyanovinyl acetate solution in CCl(4) is reported. By analyzing its relative orientations of the transition dipole moments of normal modes that cover vibrations of all chemical bonds, the three-dimensional molecular conformations and their population distributions of 1-cyanovinyl acetate are obtained, with the aid of quantum chemistry calculations that translate the experimental transition dipole moment cross angles into the cross angles among chemical bonds.     

Synthesis, structures and luminescent properties of Co(II) and Ni(II) metal-organic frameworks with semirigid diphthalic ligands

A series of transition metal coordination polymers [Co(H₃L)₂(4,4′- bpy)(H₂O)₂]_n?n(4,4′-bpy) (1), [Ni(H₂L)(4,4′-bpy)(H₂O)₂]_n (2), [Co₂(L)(phen)₂(H₂O)₄]_n?(H₂O)_2n (3), and [Ni₂(L)(phen)₂(H₂O)₄]_n?(H₂O)_2n (4) have been assembled from a semirigid multicarboxylate ligand 3,3′-(1,4-phenylenebis(oxy))diphthalic acid (H₄L) with the help of 4,4′-bipyridine (4,4′-bpy) ligand or 1,10-phenanthroline (phen) ligand. X-ray single crystal diffraction analysis reveals that complex 1 crystallizes in the space group of P − 1 and displays a one-dimensional (1D) chain structure constructed from 4,4′-bpy ligand and H₃L ligand, which was further interlinked to form a three-dimensional network via hydrogen bonds. In complex 2, Ni(II) atoms are coordinated by L ligand in monodentate fashion to form alternate left- and right-helices, which are further bridged together by the coordination interactions between Ni(II) atoms and 4,4′-bpy, leading to a 2-fold (4, 4)-connected interpenetrating network. Isostructural complexes 3 and 4 belong to the space group P − 1 and display a 1D chain structure constructed from phen and L ligands, which was further interlinked to form a 2D plane via π–π interactions. In addition, their thermal and luminescent properties were also investigated.     

Recognizing ortho-, meta- or para-positional isomers of S-methyl methoxylphenylmethylenehydrazine dithiocarboxylates by ESI-MS2: The positional effect of the methoxyl substituent

The dissociation chemistry of the ortho-, meta- or para-isomers of protonated S-methyl methoxyl- (or chloro-) benzenylmethylenehydrazine dithiocarboxylate, RPhCHN–NHC(S)–SCH₃ (R = MeO– or Cl–), has been investigated by collision induced dissociation experiments and DFT theoretical calculations. The three methoxyl-substituted isomers were easily differentiated according to the different abundance of the characteristic ion at m/z 136, resulting from the varying reactivity of the (NSC)SCH₃ elimination. This fragmentation is triggered by the positive charge upon protonation on the imine N2. Relative to the meta isomer, the positive charge on N2 in the para isomer is dispersed due to the electron donating resonance of the methoxyl group, which leads to higher energy barrier in the dissociation reaction and the less abundant product ion (m/z 136) in the MS/MS. (NSC)SCH₃ elimination of the ortho- isomer is further suppressed due to both the resonance effect and the “ortho effect” (an intramolecular hydrogen bond), with much higher energy barrier and extremely lower abundance of the fragment ion (m/z 136, 0.4%). The chloro substituted isomers, however, are short of the above positional effects due to the weak electronic effect of the substituent, and share the similar tandem mass spectrum.