Asymmetric direct vinylogous carbon-carbon bond formation catalyzed by bifunctional organocatalysts

The bifunctional chiral thiourea-tertiary amine organocatalysts have been applied to a direct asymmetric vinylogous Michael addition of α,α-dicyanoolefins to nitroolefins with 2-10 mol % catalyst loadings. The electronic properties of the thiourea-based catalysts have significant influences on this reaction. Moderate to excellent enantioselectivities (57-95% ee) have been achieved with low to good isolated yields through fine tuning the structures of the bifunctional organocatalysts. Much better ees were obtained for some α,α-dicyanoolefinic substrates compared with that catalyzed by modified cinchona alkaloids.     

Recent progress and challenges in carboxylation with CO2

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A 4-aminonaphthalimide based environmentally sensitive fluorescence probe

A simply synthesized 4-aminonaphthalimide derivative 1 expresses both polarity and viscosity sensitive fluorescence spectra, indicating its potential usage as an environmentally sensitive fluorescence probe. By comparing the fluorescence behavior of 1 with that of a known 4-aminonaphthalimide derivative 2, it was found that the substitution of the 4-amino group has profound influence on the environmentally sensitive fluorescence properties of 4-aminonaphthalimide.     

利用高吸水树脂优化3个中学化学实验*

尝试利用高吸水树脂对“酸碱中和反应、碳酸钠和碳酸氢钠分别与稀盐酸反应、探究分子运动现象”这3个实验进行创新改进,充分利用了高吸水树脂特殊的结构作用,使3个实验的现象更加显著。改进实验操作简便,高效简洁,值得推广到一线化学课堂的演示实验或学生分组实验。     

N-heterocyclic carbene catalyzed reaction of phthalaldehydes: controllable stereoselective synthesis of polyhydroxylated spiro- and fused indenones dictated by the structure of NHC catalysts

The N-heterocyclic carbene catalyzed stereoselective dimerization reactions of phthalaldehydes produced polyhydroxylated spiro- or fused indenones. The reaction pathways were dictated by the structures of NHC catalysts. Under the catalysis of a imidazole carbene, phthalaldehydes produced dihydroxylspiro[indene-2,1'-isobenzofuran]-3-ones in good to excellent yields, whereas a triazole carbene catalyzed reaction of phthalaldehydes afforded fully cis-trihydroxylindeno[2,1-a]inden-5-ones in high yields. This work not only provides a highly efficient method for the construction of valuable polyhydroxyl substituted indene derivatives that are not easily assembled by other synthetic means but also reflects the versatility of organocatalysis using N-heterocyclic carbenes.     

Enantioselective construction of quaternary carbon centre catalysed by bifunctional organocatalyst

The bifunctional thiourea-tertiary amine derivatives of simple chiral diamines serve as highly enantioselective catalysts for the Michael addition of alpha-substituted cyanoacetates to vinyl sulfones, giving an efficient protocol for the construction of an all-carbon substituted quaternary stereocentre.     

Large payload quantum steganography based on cavity quantum electrodynamics

A large payload quantum steganography protocol based on cavity quantum electrodynamics (QED) is presented in this paper, which effectively uses the evolutionary law of atoms in cavity QED. The protocol builds up a hidden channel to transmit secret messages using entanglement swapping between one GHZ state and one Bell state in cavity QED together with the Hadamard operation. The quantum steganography protocol is insensitive to cavity decay and the thermal field. The capacity, imperceptibility and security against eavesdropping are analyzed in detail in the protocol. It turns out that the protocol not only has good imperceptibility but also possesses good security against eavesdropping. In addition, its capacity for a hidden channel achieves five bits, larger than most of the previous quantum steganography protocols.     

Unravelling the Enigma of Nonoxidative Conversion of Methane on Iron Single-Atom Catalysts

The direct, nonoxidative conversion of methane on a silica-confined single-atom iron catalyst is a landmark discovery in catalysis, but the proposed gas-phase reaction mechanism is still open to discussion. Here, we report a surface reaction mechanism by computational modeling and simulations. The activation of methane occurs at the single iron site, whereas the dissociated methyl disfavors desorption into gas phase under the reactive conditions. In contrast, the dissociated methyl prefers transferring to adjacent carbon sites of the active center (Fe₁©SiC₂), followed by C−C coupling and hydrogen transfer to produce the main product (ethylene) via a key −CH−CH₂ intermediate. We find a quasi Mars–van Krevelen (quasi-MvK) surface reaction mechanism involving extracting and refilling the surface carbon atoms for the nonoxidative conversion of methane on Fe₁©SiO₂ and this surface process is identified to be more plausible than the alternative gas-phase reaction mechanism.