Novel Fréchet-type dendritic BINOL ligands and their applications in Ti(IV) complex catalyzed asymmetric addition of diethylzinc to aldehydes

New Fréchet-type dendritic BINOL ligands bearing several BINOL units at the periphery have been successfully synthesized. The (dendritic BINOL) Ti(Ⅳ) complexes were proved to be efficient catalysts for the enantioselective addition of diethylzinc to aromatic aldehydes.Moreover,these ligands could be quantitatively recovered and reused at least five times without a loss of the yield and enantioselectivity.     

Oxidative Coupling of Methane over Na-W-Mn/Si0_2 Catalysts at Elevated Pressures

Na-Mn-W/SiO2 catalysts were studied for the oxidative coupling of methane (OCM) in a micro fixed bed reactor made of stainless steel reactor at elevated pressures. The effect of operating conditions, such as GHSV, pressure, temperature and CH4/O2 ratio on the catalytic performance of OCM was investigated. The C2+ selectivity of 80.3% was obtained at a CH4 conversion of 16.1% at 750℃, 1.5×105h-1 GHSV, and 0.6 MPa. Also, there is a small output of C3 and C4 hydrocarbons in the tail gas. The results show that unfavorable effects due to elevated pressure can be overcome by increasing GHSV, and the OCM reaction is strongly dependent on the operating conditions at elevated pressures, particularly GHSV and the CH4/O2 ratio.     

Cerium(Ⅳ) ammonium nitrate(CAN) initiated O-alkylation of oximes with N-vinyl lactams

O-Alkylation of oximes with N-vinylpyrrolidin-2-one or N-methyl-N-vinylacetamide was efficiently initiated by a catalytic amount of cerium(Ⅳ) ammonium nitrate(CAN),giving the corresponding oxime ether derivatives in good yield.     

A novel way towards CdS sensitized TiO_2 nanoparticles

<正>Polymethyl methacrylate cadmium was grafted on TiO_2 surface via the surface initiated atomic transfer radical polymerization of methyl methacrylate cadmium from a surface tether initiator.The coordinated cadmium as the source precursor reacts with H_2S generates CdS nanoscrystal on TiO_2 surface.The grain size of CdS is about 5 nm and stabilized by tether polymer chains.The light absorption of CdS/TiO_2 is expanded to visible light region.     

Investigation on very large scale motions(VLSMs) and their influence in a dust storm

Based on the real-time synchronous measurements of the wind velocity,temperature,the PM10 concentration at 16 m and 47 m during a dust storm event,in which Reynolds number Re exceeds 6×106,this study reveals the existence of the very large scale motions(VLSMs) during the stable stage both in the stream velocity and the temperature field at the two heights,whose streamwise scales reach up to 10 times the thickness of the boundary layer.The streamwise velocity and the PM10 concentration display a similar frequency corresponding to the peaks of their energy spectra,which implies that the VLSMs of streamwise flow have a significant role in dust transportation.In contrast,the salient deviations of the PM10 concentration at 47 m from the Gaussian distribution are revealed,which means that 47 m is not in the dust transportation layer,but is a region where the dust transportation layer and the outer flow intersect each other.Analysis demonstrates that the energy spectra of the PM10 concentrations at 16 m and 47 m display the "-1" scaling law feature,which has the same frequency range(0.001-0.1 Hz) as that of the wind velocity.This provides a new paradigm for the existence of the self-similarity scaling region in turbulent flow.     

Highly efficient oxidation of alcohols using Oxone~ as oxidant catalyzed by ruthenium complex under mild reaction conditions

Aromatic and alkyl alcohols were oxidized to the corresponding aldehydes or ketones at room temperature with high conversion and selectivity using Oxone(?)(2KHSO_5·KHSO_4·K_2SO_4)as oxidant catalyzed by ruthenium complex Quin-Ru-Quin(where Quin = 8-hydroxyquinoline).The reaction time is very short and the preparation of complex is simple.     

Two New Compounds from Melanosciadum pimpinelloideum H. Boiss

Melanosciadum pimpinelloideum H. Boiss (Umbelliferae), an indigenous plant，is the unique representative of species Melanosciadum1. Anomalin and 3(-angeloyl-4(-hydroxy-trans-khellactone were isolated from this plant2. In this investigation, from the whole plants two new compounds, melanochromone 1 and 2-ethoxyl-2-(4-hydroxyphenyl)ethanol 2 were isolated with known compounds 1-(4-hydroxyphenyl)-1,2-ethanediol 33, tymine (5-methyluracil) 44, cimifugin 55, umtatin 65, bergenin 76, daucosterol 87…     

Theoretical study of the mechanism for C-H bond activation in spin-forbidden reaction between Ti~+ and C_2H_4

The mechanism of the spin-forbidden reaction Ti+(4F, 3d24s1) + C2H4 → TiC2H2+ (2A2) + H2 on both doublet and quartet potential energy surfaces has been investigated at the B3LYP level of theory. Crossing points between the potential energy surfaces and the possible spin inversion process are discussed by means of spin-orbit coupling (SOC) calculations. The strength of the SOC between the low-lying quartet state and the doublet state is 59.3 cm-1 in the intermediate complex IM1-4B2. Thus, the changes of its ...     

Oxidation of 3,4-dihydropyrimidin-2（1H）-ones with nitrosonium （NO^＋）

3,4-Dihydropyrimidin-2(1H)-ones (DHPMs) were oxidized with 1.2 equiv. of nitrosonium tetrafluoroborate (NO⁺BF₄⁻) to pyrimidin-2(1H)-ones in acetonitrile at room temperature in high yields.     

An Efficient Cationic Cyclization Approach for the Construction of Labdane Diterpenoid Decalin Ring Skeleton

An effective approach for the construction of the decalin ring skeleton of labdane diterpenoids was developed based on a key biomimetic cationic polyene cyclization of an epoxy allylsilane precursor. The synthetic approach demonstrated here would be useful in the enantioselective and diastereoselective total synthesis of natural labdane diterpenoids in general.