Chiral Phosphoric Acid Catalyzed Asymmetric Ugi Reaction by Dynamic Kinetic Resolution of the Primary Multicomponent Adduct

Reaction of isonitriles with 3‐(arylamino)isobenzofuran‐1(3H)‐ones in the presence of a catalytic amount of an octahydro (R)‐binol‐derived chiral phosphoric acid afforded 3‐oxo‐2‐arylisoindoline‐1‐carboxamides in high yields with good to high enantioselectivities. An enantioselective Ugi four‐center three‐component reaction of 2‐formylbenzoic acids, anilines, and isonitriles was subsequently developed for the synthesis of the same heterocycle. Mechanistic studies indicate that the enantioselectivity results from the dynamic kinetic resolution of the primary Ugi adduct, rather than from the C?C bond‐forming process. The resulting heterocycle products are of significant medicinal importance.     

Design of Enhanced Catalysts by Coupling of Noble Metals (Au,Ag) with Semiconductor SnO2 for Catalytic Reduction of 4‐Nitrophenol

The reduction of 4‐nitrophenol (Nip) into 4‐aminophenol (Amp) by NaBH₄, which is catalyzed by both binary and ternary yolk–shell noble‐metal/SnO₂ heterostructures, is reported. The binary heterostructures contain individual Au or Ag nanoparticles (NPs) and the ternary heterostructures contain both Au and Ag NPs. The Au@SnO₂ yolk–shell NPs are synthesized via a silica seeds‐mediated hydrothermal method. Subsequently, the Au@SnO₂@Ag and Au@SnO₂@Au yolk–shell–shell (YSS) NPs are synthesized, whereby SnO₂ is located between the Au and Ag NPs. The morphology, composition, and optical properties of the as‐prepared samples are analyzed. For the binary heterostructures, the rate of the reduction reaction increases with decreasing particle size. The catalytic results demonstrate the synergistic effect of Au and Ag in the ternary metal–semiconductor heterostructures, which is beneficial to the catalytic reduction of Nip into Amp. Both the binary and ternary heterostructures exhibit significantly better catalytic performances than the corresponding bare Au and Ag NPs. It is envisaged that the current synthesized strategy will promote further interest in the field of bimetal NP‐based catalysis.     

Highly efficient TfOH-catalyzed head-to-tail dimerization of vinylarenes

A convenient and efficient TfOH-catalyzed head-to-tail dimerization of vinylarenes has been realized under mild conditions. The present protocol provides an attractive approach to a diverse range of higher olefins in good to excellent yields.     

Chemical Constituents from Termite‐associated Xylaria acuminatilongissima YMJ623

Three previously unreported benzofurans, namely acumifurans A–C ( 1 – 3 ), along with five known compounds, 2‐(isopropyl‐1′‐ol)‐2,3‐dihydrobenzofuran‐5‐carbinol ( 4 ), fomannoxin alcohol ( 5 ), fomannoxin ( 6 ), acremine S ( 7 ) and cyclo(L ‐Pro‐L ‐Leu) ( 8 ), were isolated from the ethyl acetate extracts of the fermented broths of termite n est associated Xylaria acuminatilongissima YMJ623. Compound 4 , a synthe tic benzofuran analogue of 1 – 3 , was isolated for the first time from natural resources. The str uctures of 1 – 8 were determined through spectroscopic data analyses. The absolute configurations of 1 – 4 were established based mainly on ROESY experiment and Mosher’s reaction, and compared the optical rotation data with the literatures. The effects of these compounds on the inhibition of NO production in lipopolysaccharide (LPS)‐activated murine macrophage RAW264.7 cells were also evaluated. Of the compounds tested, 6 showed a mild NO production inhibitory activity without any cytotoxicity, and its mean maximum inhibition (E_max) at 100 μM was 42.98±0.87 %.     

具有线性微分算子的分数阶微分方程积分边值问题

研究一类具有分数阶线性微分算子的非线性微分方程积分边值问题解的存在性与唯一性.利用Schauder不动点定理及压缩映射原理,建立并证明了边值问题解的存在性定理和唯一性定理,并给出两个例子以说明所得结论.     

Line-Pro le Analysis of Excitation Spectroscopy in the Even 3p5(2P1/2)nl'[K']J(l'=1,3) Autoionizing Resonances of Ar

The even-parity autoionizing resonance series 3p⁵np'[3/2]_1,2, 3p⁵np'[1/2]₁, and 3p⁵nf'[5/2]₃ of Ar have been investigated exciting from the two metastable states 3p⁵4s[3/2]₂ and 3p⁵4s'[1/2]₀ in the photon energy range of 32500-35600 cm^-1 with an experimental bandwidth of ~0.1 cm^-1. The excitation spectra of the even-parity autoionizing resonance series show typical asymmetric line shapes. New level energies, quantum defects, line profile index and resonance widths, resonance lifetime and reduced widths of the autoionizing resonances are derived by a Fano-type line-shape analysis. The line profile index q and the resonance widths Γ are shown to be approximately proportional to the effective principal quantum number n^*. The line separation of the 3p⁵np' autoionizing resonances is discussed.