Ruthenium(II)-Catalyzed Asymmetric Inert C−H Bond Activation Assisted by a Chiral Transient Directing Group

A ruthenium(II)-catalyzed asymmetric intramolecular hydroarylation assisted by a chiral transient directing group has been developed. A series of 2,3-dihydrobenzofurans bearing chiral all-carbon quaternary stereocenters have been prepared in remarkably high yields (up to 98 %) and enantioselectivities (up to >99 % ee). By this methodology, a novel asymmetric total synthesis of CB2 receptor agonist MDA7 has been successfully developed.     

杂原子掺杂提升四氧化三钴电催化性能

正发展电解水制氢和金属-空气电池等电化学能源转化与存储技术对于解决日益严峻的能源短缺和环境污染问题具有重要意义~1。氧气析出反应(OER)是电解水制氢和金属-空气电池的关键半反应,但其缓慢的动力学过程却限制了上述能源技术的快速发展~(2,3)。钌/铱基催化剂是当前最为有效     

Pathway from N‐Alkylglycine to Alkylisonitrile Catalyzed by Iron(II) and 2‐Oxoglutarate‐Dependent Oxygenases

N‐alkylisonitrile, a precursor to isonitrile‐containing lipopeptides, is biosynthesized by decarboxylation‐assisted ‐N≡C group (isonitrile) formation by using N‐alkylglycine as the substrate. This reaction is catalyzed by iron(II) and 2‐oxoglutarate (Fe/2OG) dependent enzymes. Distinct from typical oxygenation or halogenation reactions catalyzed by this class of enzymes, installation of the isonitrile group represents a novel reaction type for Fe/2OG enzymes that involves a four‐electron oxidative process. Reported here is a plausible mechanism of three Fe/2OG enzymes, Sav607, ScoE and SfaA, which catalyze isonitrile formation. The X‐ray structures of iron‐loaded ScoE in complex with its substrate and the intermediate, along with biochemical and biophysical data reveal that ‐N≡C bond formation involves two cycles of Fe/2OG enzyme catalysis. The reaction starts with an Fe^IV‐oxo‐catalyzed hydroxylation. It is likely followed by decarboxylation‐assisted desaturation to complete isonitrile installation.     

Crystallization Mechanism of 9,9-Diphenyl-dibenzosilole from Solids

Organic semiconductor (OSC) crystals have great potential to be applied in many fields, as they can be flexibly designed according to the demands and show an outstanding device performance. However, OSCs with the capacity of solid-state crystallization (SSC) are developing too slowly to meet demands in productions and applications, due to their difficulties in molecular design and synthesis, unclear mechanism and high dependence on experimental conditions. In this work, in order to solve the problems, we synthesized an organic semiconductor capable of SSC at room temperature by adjusting the relationship between conjugated groups and functional groups. The thermodynamic and kinetic properties have been studied to discover the model of film SSC. Moreover, it can be purposefully controlled to prepare the high-quality crystals, and their corresponding organic electronic devices were further fabricated and discussed.     

Weakly Hamiltonian-connected locally semicomplete digraphs

We characterize weakly hamiltonian-connected locally semicomplete digraphs. Our result extends those of Thomassen. (J. Combinatorial Theory B 28 (1980), 142–163) for tournaments. © 1996 John Wiley & Sons, Inc.     

A Double-Site Chemodosimeter for Selective Fluorescence Detection of a Nerve Agent Mimic

A novel two-site chemodosimeter (SWJT-4) based on fluorescein skeleton to detect diethyl chlorophosphate (DCP) was designed and synthesized. It is a turn-on fluorescent probe for DCP with good selectivity and obvious color change in aqueous solution. Interestingly, the two oxime groups of SWJT-4 as dual response sites initiated different reactions with DCP to form a cyano group and an isoxazole ring, respectively. The corresponding mechanism was confirmed by ¹H NMR, MS and DFT calculation. Moreover, SWJT-4 could be used as a fluorescent test paper to detect DCP vapor.     

New existence of multi-spike solutions for the fractional Schr?dinger equations

We consider the following fractional Schr¨odinger equation:(-?)^su + V(y)u = u^p, u > 0 in R^N,(0.1) where s ∈(0, 1), 1 < p 相似文献   

Unraveling the reactivity of a cationic iminoborane: avenues to unusual boron cations

A cationic terminal iminoborane [Mes*N B ← IPr₂Me₂][AlBr₄] (3⁺[AlBr₄]⁻) (Mes* = 2,4,6-tri-tert-butylphenyl and IPr₂Me₂ = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) has been synthesized and characterized. The employment of an aryl group and N-heterocyclic carbene (NHC) ligand enables 3⁺[AlBr₄]⁻ to exhibit both B-centered Lewis acidity and BN multiple bond reactivities, thus allowing for the construction of tri-coordinate boron cations 5⁺–12⁺. More importantly, initial reactions involving coordination, addition, and [2 + 3] cycloadditions have been observed for the cationic iminoborane, demonstrating the potential to build numerous organoboron species via several synthetic routes.

An NHC-stabilized aryliminoboryl cation exhibits both boron-centered Lewis acidity and multiple bond reactivity and could be utilized as an effective synthon for unusual cationic boron species.     

p型G aSb窗口层在热光伏电池中的应用研究

为了提高GaSb热光伏电池的转换效率,在电池结构中引入p+-GaSb窗口层,研究了生长基底、衬底温度和反应物源温度对p+-GaSb薄膜性能的影响,并优化了电池结构中p+-GaSb窗口层的厚度和掺杂浓度.实验结果表明,生长基底和温度等制备参数影响着p+-GaSb薄膜的结构特性和电学特性,而且,较薄的高掺杂p+-GaSb层有利于提高电池性能.通过测试和仿真,热光伏电池的转换效率达到9.49;(AM1.5测试)和20.34;(AFORS-HET仿真).     

Controllable soliton transition and interaction in nonlocal nonlinear media

Nonlinear Dynamics - Two kinds of controllable evolutions of optical solitons are predicted in nonlocal nonlinear media by gradually tuning the characteristic length of response function. On the...