Highly efficient iridium catalyst for asymmetric transfer hydrogenation of aromatic ketones under base-free conditions

[reaction: see text] Catalytic systems generated in situ from the chiral PNNP ligands with iridium or rhodium hydride complexes exhibited excellent catalytic activity and good enantioselectivity in the asymmetric transfer hydrogenation of aromatic ketones without added base. The best result was obtained in the IrH(CO)(PPh(3))(3)-ligand 2 catalytic system with up to 99% yield and 97% ee.     

Tin Mediated Allylation of Aldimines with Allyl Bromide

SyntheticinterestsinhighlyfunctionalizedacyclicandcyclicamineshavecontributedtothewealthofexPerimentalmethodologydeveloPedfortheadditionofcarbanionstothecarbon-nitrogendoublebondofimines.Generally,organometallicreagentsorilltermedi-atesareusedascarbanionsandadditionofallylicorganometallicspeciestothenieconshtutesavaluablemethodforthesynthesisofhomoallylamines.'Amongthese,allyLlithium,'-magnesium,'-zinc,'-boraneandboronate,'-silaneand-stannane'havebeenusedforallylationofdriines.Ontheotherhand,…     

2020 Roadmap on two-dimensional nanomaterials for environmental catalysis

This roadmap demonstrates a series of two-dimensional nanomaterials, such as graphene, black phosphorus, oxides, layered double hydroxides, chalcogenides, bismuth-based layered compounds, MXenes, metal organic frameworks, covalent organic frameworks, and others, for environmental catalysis.     

微型柱在线分离-ICP-MS法测定高纯氧化铕中的14个稀土杂质

研究了微型柱在线分离-电感耦合等离子质谱法（ICP-MS）测定高纯Eu2O3中痕量Tm的方法，研制了Cyanex272负载树脂微型分离柱，优化了分离Eu2O3基体的实验条件，在线分离测定时间为25min。建立了在线柱分离测定Tm，内标补偿法直接测定其余稀土杂质的高纯Eu2O3中14个稀土杂质的ICP-MS分析方法。方法检出限为0.01μg/g-0.15μg/g，加标回收率为91.5%-110%,相对标准偏差为1.7%-4.9%。可满足快速测定99.999%Eu2O3中14个稀土杂质的要求。     

3-甲基-1-苯基-4-{4-([5-甲基-2-(4-取代芳基)-噁唑-4-基]甲氧基)-芳亚甲(苄)基}-2-吡唑啉-5-酮的设计、合成与降血糖活性

设计合成了具有降血糖活性的3-甲基-1-苯基-4-[4-[[5-甲基-2-(4-取代芳基)-噁唑-4-基]甲氧基]-芳亚甲(苄)基]}-2-吡唑啉-5-酮类化合物.用丁二酮单肟和(取代的)苯甲醛环合、氯化得到氯甲基噁唑衍生物,与对羟基苯甲醛或香兰醛缩合,再与3-甲基-1-苯基-2-吡唑啉-5-酮进行Knoevenagel反应及催化氢化得到目标化合物(Ⅰ和Ⅱ),共合成了16个未见文献报道的新化合物,并利用元素分析、IR、MS和1HNMR确证了化合物的结构.初步药理试验结果表明,所合成的化合物有抑制血糖升高的倾向以及能明显加强和延长外源性胰岛素的降血糖作用,其中化合物Ⅰb,Ⅰd和Ⅰf尤为突出,说明这类化合物可能有增强胰岛素敏感性的作用.     

Hydrogen bonding and halogen bonding co-existing in the reaction of heptafluorobenzyl iodide with N,N,N,N-tetramethylethylene diamine

Two novel assembling systems 3 and 4, with the structures of C₆F₅CF₂⁻?H⁺N(Me)₂CH₂CH₂(Me₂)N⁺H?⁻CF₂C₆F₅ and C₆F₅CF₂I?N(Me)₂CH₂CH₂(Me)₂N?ICF₂C₆F₅, respectively, have been generated from the solution of heptafluorobenzyl iodide 1 and N,N,N^′,N^′-tetramethylethylenediamine 2 in dichloromethane. Their structures have been characterized by X-ray diffraction analysis, NMR and IR spectroscopy. Intermolecular N?I halogen bond and F?H hydrogen bond are revealed to be the driving forces for their formation.     

Ion/molecule reactions in a miniature RIT mass spectrometer

Ion/molecule reactions were explored in a newly developed miniature mass spectrometer fitted with a rectilinear ion trap (RIT) mass analyzer. The tandem mass spectrometry performance of this instrument is demonstrated using collision induced dissociation (CID) and ion/molecule reactions. The latter includes Eberlin transacetalization reactions and electrophilic additions. Selective detection of the chemical warfare simulant dimethyl methyl phosphonate (DMMP) was achieved through selective Eberlin reactions of its characteristic phosphonium fragment ion CH3OP(+)(O)CH3 (m/z 93), with 1,4-dioxane or 1,3-dioxolane. Efficient adduct formation as a result of electrophilic attack by the phosphonium ion on various nucleophilic reagents, including 1,1,3,3-tetramethyl urea, methanesulfonic acid methyl ester, dimethyl sulfoxide and methyl salicylate, was also observed using the RIT device. The product ions of these reactions were analyzed using CID and the characteristic fragmentation patterns of the ionic addition products were recorded using multiple-stage experiments in the miniature RIT instrument. This study clearly demonstrates that a small, home-built, miniature RIT mass spectrometer can be used to perform analytically useful ion/molecule reactions and also that instruments like this have the potential to provide a portable platform for in situ detection of organophosphorus esters and related compounds with high specificity using tandem mass spectrometry.     

Proteomic analysis of apoptosis initiation induced by all-trans retinoic acid in human acute promyelocytic leukemia cells

The irreversible destiny of apoptosis in its early stage might play a critical role in the apoptosis of human acute promyelocytic leukemia (APL) cell line induced by all-trans retinoic acid (ATRA). To characterize protein alterations during the apoptosis-initiation phase and to understand the metabolic status at that time, we investigated the protein profiles in the apoptosis-initiation phase of APL cell line HL-60 by proteomic analysis. ATRA-withdrawal was conducted to demonstrate that there was committed initiation phase of apoptosis triggered by 10(-6) M ATRA at day 3. Only after that time point, ATRA-treated cells irreversibly went to apoptosis. Also at that time point, the positive regulators of apoptosis such as STAT3 increased at protein level, whereas negative regulators (Bcl-2 and p-STAT3) decreased. In addition, caspase-3 also increased after that time. Furthermore, comparative proteomic analysis was utilized to examine the protein expression profiles during the initiation stage of apoptosis. Our results showed 12 upregulated and 7 downregulated proteins experiencing twofold alteration, including key regulators of signal transduction such as G-proteins and nucleic receptors, proteins related with metabolism, oxidation and reduction, proteins associated with the nucleus and cytoskeleton-related proteins. Some of them could be positive modulators to trigger apoptosis, whereas others could contribute to intracellular defense against apoptosis induced by exogenous triggers. The results above suggest that there is a subtle balance between apoptosis and the intracellular defense against apoptosis. Once the balance is disturbed, cells would irreversibly initiate to undergo the execution of apoptosis.     

Itosides A – I,New Phenolic Glycosides from Itoa orientalis

Eight new benzoylated gentisyl alcohol (=2‐(hydroxymethyl)benzene‐1,4‐diol) glucosides, itosides A–H ( 1 – 8 ), together with the new pyrocatechol (=benzene‐1,2‐diol) glycoside itoside I ( 9 ) were isolated from the bark and twigs of Itoa orientalis (Flacourtiaceae). In itosides B–D ( 2 – 4 ), the gentisyl alcohol moiety was esterified by 1‐hydroxy‐6‐oxocyclohex‐2‐ene‐1‐carboxylic acid, while itosides E–H ( 5 – 8 ) contained instead an additional 2‐hydroxybenzoic acid moiety. The compounds were accompanied by the known derivatives 4‐hydroxytremulacin ( 10 ), poliothyrsoside ( 11 ), poliothyrsin ( 12 ), homaloside D ( 13 ), tremulacin, and pyrocatechol β‐D ‐glucopyranoside. The structures of the new compounds were elucidated by spectral and chemical methods.     

Kinetic determination of organic vapor mixtures with single piezoelectric quartz crystal sensor using artificial neural networks

A single piezoelectric quartz crystal coated with one kind of crown ether was applied to the simultaneous determination of binary acid and amine vapor mixtures. From the adsorption and desorption curves of analytes, which were somewhat different in shape, frequency shifts from ten time windows were taken as inputs for artificial neural networks (ANN). Prediction results were satisfactory for ANN in both sample sets. The average relative errors, for formic acid and acrylic acid were 5%, for n-butylamine and aniline, they were 3% with ANN respectively. The effects of number of neurons in the hidden layer of ANN on the performance of the network are also discussed.