Synthesis of Imides by Palladium‐Catalyzed C?H Functionalization of Aldehydes with Secondary Amides

An efficient palladium‐catalyzed C? H functionalization of aldehydes with various N‐substituted N‐heteroarene‐2‐carboxamides has been developed for the synthesis of secondary imides. The reaction tolerates various functionalities, such as methoxy, fluoro, chloro, and bromo groups. A tentative radical mechanism for a Pd^II/Pd^IV catalytic cycle is proposed.     

Structure-Activity Relationship, Cytotoxicity and Mode of Action of 2-Ester-substituted 1,5-Benzothiazepines as Potent Antifungal Agents

Our studies examined the structural features responsible for the antifungal activity of 2-ethoxycarbonyl-1,5- benzothiazepine （7a）. Three series of 1,5-benzothiazepine derivatives were synthesized and screened for their antifungal activity. The results suggested that the ethoxycarbonyl group at the 2 position and the imine moiety on the seven-membered ring are essential for activity. The most potent of the synthesized analogues （7a, 7b） were further studied by evaluating their cytotoxicity and mode of action （for 7a）. The results showed that compounds 7a and 7b were relatively safe for BV2 cells, but compound 7a interfered with Cryptococcus neoformans cell wall integrity by increasing the chitinase activity. Therefore, compound 7a was considered safe as an antifungal agent for animal cells.     

Liquid fragility of the unsaturated polyester resin

Curing behaviors of the unsaturated polyester resin (UPR) containing 1–1.8 wt% methyl ethyl ketone peroxide (MEKP) initiator are investigated. The viscosity, gelation and vitrification transition of the UPR-MEKP systems are examined using the rotating viscometer and differential scanning calorimetry (DSC). A liquid fragility parameter, M _c, defined as the viscosity variation rate of the liquids towards the curing temperature is presented. It is found that M _c has a good negative relation with the glass transition temperature (T _g) in the systems. M _c can be used for predicting the stability of the cured amorphous systems. The relationship between the liquid and cured thermoset polymer systems is studied from both the thermodynamic and kinetic point of view.     

LC–MS/MS法测定动物性食品中万古霉素残留

建立液相色谱–串联质谱(LC–MS/MS)法检测动物性食品中万古霉素药物残留的方法。用磷酸盐缓冲溶液对动物性食品中的万古霉素进行提取,经HLB固相萃取柱净化,采用电喷雾离子源,以正离子检测方式进行质谱分析。实验结果表明,万古霉素质量浓度在1~500μg/L范围内与色谱峰面积呈良好的线性,相关系数r=0.998。低、中、高3个质量浓度添加水平的回收率为84.8%~118.2%,相对标准偏差为2.2%~7.2%(n=5),检出限为2μg/kg。     

The first mu3-oxalato-bridged copper complex with tridentate Schiff base ligand N-ethyl-N'-salicylidene-1,2-diaminoethane: synthesis,structure, and magnetic properties

The first mu(3)-oxalato-bridged copper(II) complex, [[Cu(3)(L)(3)(mu(3)-C(2)O(4))][Cu(L)(H(2)O)](ClO(4))(2)] x 0.5(H(2)O) x 0.5(CH(3)OH), where HL = N-ethyl-N'-salicylidene-1,2-diaminoethane, has been synthesized and characterized by variable-temperature magnetic susceptibility measurement. The complex exhibits ferromagnetic coupling between the oxalato-bridged copper atoms and antiferromagnetic coupling between the oxygen-bridged copper atoms.     

A Study of the Interaction Between Cucurbit[8]uril and Alkyl‐Substituted 4‐Pyrrolidinopyridinium Salts

The interaction between cucuribit[8]uril (Q[8]) and a series of 4‐pyrrolidinopyridinium salts bearing aliphatic substituents at the pyridinium nitrogen, namely 4‐(C₄H₈N)C₅H₅NRBr, where R=Et (g1), n‐butyl (g2), n‐pentyl (g3), n‐hexyl (g4), n‐octyl (g5), n‐dodecyl (g6), has been studied in aqueous solution by ¹H NMR spectroscopy, electronic absorption spectroscopy, isothermal titration calorimetry and mass spectrometry. Single crystal X‐ray diffraction revealed the structure of the host–guest complexes for g1, g2, g3, and g5. In each case, the Q[8] contains two guest molecules in a centrosymmetric dimer. The orientation of the guest molecule changes as the alkyl chain increases in length. Interestingly, in the solid state, the inclusion complexes identified are different from those observed in solution, and furthermore, in the case of g3, Q[8] exhibits two different interactions with the guest. In solution, the length of the alkyl chain plays a significant role in determining the type of host–guest interaction present.     

Bis(μ‐6‐hydroxy­picolinato)‐μ‐oxo‐bis­[di­pyridine­manganese(III)] monohydrate

The title compound, [Mn₂(μ‐O)(C₆H₃NO₃)₂(C₅H₅N)₄]·H₂O, was isolated from the reaction of 2,6‐pyridine­di­carboxylic acid with [Mn₁₂O₁₂(CH₃COO)₁₆(H₂O)₄] in pyridine. The dimanganese complex has twofold symmetry; the Mn^III atoms are bridged by one oxo and two amidate ligands and show compressed octahedral Jahn–Teller distortion. The molecular packing comprises a three‐dimensional structure constructed by means of extensive intermolecular interactions, including three kinds of hydrogen bonds and π–π interactions.     

An efficient method for constructing nonorthogonal localized molecular orbitals

A new method for constructing nonorthogonal localized molecular orbitals (NOLMOs) is presented. The set of highly localized NOLMOs is obtained by minimization of the spread functional starting from an initial set of canonical orthogonal molecular orbitals. To enhance the stability and efficiency, the centroids of the NOLMOs are constrained to be those of the corresponding orthogonal localized molecular orbitals (OLMOs), which are obtained with the Boys criterion in advance. In particular, these centroid constraints make the optimization for each NOLMO independent of the others, which is an attractive feature for application to large systems. The minimization with the constraints incorporated through the multiplier-penalty function method is stable and efficient in convergence. While exhibiting the classical bonding pattern in chemistry and sharing a spatial distribution similar to that of the corresponding OLMOs, the obtained NOLMOs are more compact than the corresponding OLMOs with about 10%-28% reduction in the value of the spread functional and devoid of the troublesome "orthogonalization tails."     

Transition‐Metal Chemistry of Alkaline‐Earth Elements: The Trisbenzene Complexes M(Bz)3 (M=Sr,Ba)

We report the synthesis and spectroscopic identification of the trisbenzene complexes of strontium and barium M(Bz)₃ (M=Sr, Ba) in low‐temperature Ne matrix. Both complexes are characterized by a D₃ symmetric structure involving three equivalent η⁶‐bound benzene ligands and a closed‐shell singlet electronic ground state. The analysis of the electronic structure shows that the complexes exhibit metal–ligand bonds that are typical for transition metal compounds. The chemical bonds can be explained in terms of weak donation from the π MOs of benzene ligands into the vacant (n?1)d AOs of M and strong backdonation from the occupied (n?1)d AO of M into vacant π* MOs of benzene ligands. The metals in these 20‐electron complexes have 18 effective valence electrons, and, thus, fulfill the 18‐electron rule if only the metal–ligand bonding electrons are counted. The results suggest that the heavier alkaline earth atoms exhibit the full bonding scenario of transition metals.