First example of the coupling of α-diazoketones with thiourea: a novel route for the synthesis of 2-aminothiazoles

α-Diazoketones undergo smooth coupling with thiourea in the presence of 10 mol % of copper(II) triflate to produce the corresponding 2-aminothiazoles in excellent yields with high selectivity. The use of copper(II) triflate makes this method simple, convenient and practical. This method works well with both aryl and alkyl diazoketones to furnish a wide range of 2-aminothiazoles.     

Calculations of Hyperpolarizabilities for Para-disubstituted Benzenes with the QSPR

A quantitative structure-property relationship (QSPR) was made for the prediction of the hyperpolarizabilities(β) ofpara-disubstituted benzenes with the nonlinear optical properties, and the βcal2 calculated by this model accorded better with the experimental values (βexpt) compared with theβcal1 calculated at the CPHF/6-31G*//HF/STO-3G level of theory, especially whenβ was big.     

Theoretical study of mechanism and kinetics for the reaction of hydroxyl radical with 2′-deoxycytidine

The reaction mechanism and kinetics for the abstraction of hydrogen and addition of hydroxyl radical (OH) to 2′-deoxycytidine have been studied using density functional theory at MX06-2X/6-311+G(d,p) level in aqueous solution. The optimized geometries, energies, and thermodynamic properties of all stationary points along the hydrogen abstraction reaction and the addition reaction pathways are calculated. The single-point energy calculations of the main pathways at CCSD(T)/6-31+G(d,p)//MX06-2X/6-311+G(d,p) level are performed. The rate constants and the branching ratios of different channels are evaluated using the canonical variational transition (CVT) state theory with small-curvature tunneling (SCT) correction in aqueous solution to simulate the biological system. The branching ratios of hydrogen abstraction from the C1′ site and the C5′ site and OH radical addition to the C5 site and the C6 site are 57.27% and 12.26% and 23.85% and 5.69%, respectively. The overall calculated rate constant is 4.47?×?10⁹ dm³ mol^?1 s^?1 at 298 K which is in good agreement with experiments. The study could help better understand reactive oxygen species causing DNA oxidative damage.     

Spectroscopic Study of the Interaction of Bu_2SnCl_2 with EHPG

A number of Sn (Ⅳ)complexes have been synthesized since 1980 and tested its anticancer activity1. The simplest complex Bu2SnCl2 has activity to P388 tumor cells. Several metal complexes such as Ru-ind (trans-indazolium (bisindazole) tetrachloro- ruthenate (Ⅲ)) had used transferrin as a drug delivery system, the complexes still exhibit high antitumor activity and lower toxicity2. We use EHPG as a model ligand3 to study the interaction between Bu2SnCl2 and EHPG. EHPGAt first, we stud…     

Facile Method for the Synthesis of Vicinal Azidoiodides by the Reaction of the NaN3–I2 System with Unsaturated Compounds

A facile and efficient method was developed for the synthesis of vicinal azidoiodides in 62–77% yields by the reaction of sodium azide and iodine with unsaturated compounds in methanol, aqueous methanol, or the water–methanol–tetrahydrofuran solvent system. The reaction in Et₂O or CHCl₃ produced only vicinal diiodides.     

New Catalyst for the Copolymerization of Styrene with Carbon Monoxide

Carbonmonoxide(CO)witholefinscanbec0p0lymerizedwithfreeradicalinitiatorsorn0bletransitionmetalc0mpoundcatalystS.Thefreeradicalinitiatedcopolymerizationunderhighgaspressure(upt0l(X)Mpa)andl2O-l65oC',whereasthemostusednobletransitionmetalcompoundsf0rthec0polymerizati0nofcarbonmonoxidewitholefinsarepalladiumorrhodiumcompounds"'.In0urw0rk,theneodymiumcomp0undcatalystsystemswerefoundt0beactiveforthecopolymerizationofstyreneandcarbonm0noxide.Thecopolymerizationofstyreneandcarbonm0n0xidewascAned0u…     

Synthesis and Structure of the Complexes of 2-Alkoxycarbonylalkyltin Trichlorides with 2-Salicylideneaminophenol

SinceHutton]developedanovelr0utet0preparationofthe2-alkoxycarbonylalkyltintrichIorides,R'OCOCHRCH,SnCI,(l),lhavereceivedconsiderableattenti0nbecauseofthevarietyofcoordinationgeometriesaboutthetinatom.2-'Previ0usly,wehadre-portedtheadducts0flwithneutraIdonorssuchasDMSO,HMPA,bpyandphen.'-'Inthispaper,wereportthesynthesis0fthecomplexes0flwithnegativebivaIentligandderivedfr0m2-salicylideneamin0phenop(H2L),R'OCOCHRCH,SnClL(R=H,Me,R'=Me,Et,n-Pr,Allyl,n-Bu),andthecrystaIstructureof…     

Effect of CeO_2 Promoter on the Performance of Catalyst for CH_4, CO_2with O_2 to Synthesis Gas

Inrecentyears,thereactionofmethane,carbondioxidewithoxygentosynthesisgashasbeenreceivingmore.attentionfromthevieWPointofPrpservingglobalenvironment,becauseCH#andCO,areofgreenhousegasesandtheircontributiontoglobalwarmingisverylargeowingtotheirhugeamountreleasedintheatmosphere'.Inaddition,therearetwoadvantagesinthisprocessobviously,bychangingtheratiooffeed,itcanachievethermalneutralizingandtheCO/H,ratiocanlbebovariedintherangeof0.5~ltofitdifferentindustrialrequirement.Therearehardlyanypapers…     

Influence of Sulfation on the Catalytic Activity of Ni-ZrO2 for NO Reduction with Propane in Excess Oxygen

Selective catalytic reduction （SCR） of nitric oxide with propane in excess oxygen was investigated on Ni-ZrO2 （NZ） and sulfated Ni-ZrO2 （SNZ）, prepared by coprecipitation from a mixture of nickel nitrate-zirconium oxychloride followed by modifying with （NH4）2SO4. It was found that sulfated Ni-ZrO2 catalyst showed higher activity for the SCR of NO with propane than that of Ni-ZrO2. The structural and surface properties of catalysts were studied by XRD, BET, SEM and FT-IR of pyridine adsorption. The experimental results indicated that the modification of （NH4）2SO4 resulted in the generation of strong BrOnsted and Lewis acid sites and promoted the dispersion of the Ni species, which could lead to higher NO conversion and propane efficiency in NO reduction.     

On the Reaction Mechanism of Br2 with OCS

The reaction mechanism of photochemical reaction between Br2 (^1∑) and OCS (^1∑) is predicted by means of theoretical methods. The calculated results indicate that the direct addition of Br2 to the CS bond of OCS molecule is more favorable in energy than the direct addition of Br2 to the CO bond. Furthermore, the intermediate isomer syn-BrC(O)SBr is more stablethe rmodynamically and kinetically than anti-BrC(O)SBr. The original resultant anti-BrC(O)SBr formed in the most favorable reaction channel can easily isomerize into the final product syn-BrC(O)SBr with only 31.72 kJ/mol reaction barrier height. The suggested mechanism is in good agreement with previous experimental study.     

Influence of Pretreatment on the Interaction of Oxygen with Silver and the Catalytic Activity of Ag／SiO2 Catalysts for CO Selective Oxidation in H2

The interactions of oxygen with pre~reduced silver catalysts as well as their catalytic propertiesfor CO selective oxidation in H2 after oxygen pre-treatment are studied in this paper. It is found that the pretreatment exerts a strong influence on the activity and selectivity of the silver catalyst. A drop in activity and selectivity is observed after treating a pre-reduced catalyst with oxygen at low temperatures,whereas a converse result is obtained after an oxidizing treatment at high temperatures (T≥350℃). O2-TPD results show that surface oxygen species adsorbs on silver surface after the oxygen treatment at low temperatures. However, penetration of oxygen into the silver is enhanced by a high temperature treatment, meanwhile the surface oxygen species disappear. No other silver species except metallic silver are observed on all the catalysts by XRD, and the size of silver particle is not changed after the treatment with oxygen at low temperatures. The surface oxygen species formed by oxygen treatment can also be removed by hydrogen reduction. The strongly-adsorbed surface oxygen species prohibit the adsorption and diffusion of oxygen species in reaction gas on the surface of silver catalyst, causing the decrease in CO oxidation activity, in other words, it is important to obtain a clean silver surface for increasing the catalyst activity in CO removal from H2-rich feed gas. The differences in activity and selectivity due to the oxygen pretreatment at different temperatures axe discussed in terms of the changes in the surface/subsurface oxygen species of the silver particles.     

Measurement of the rate constants for the reactions of the IO• radical with sulfur-containing compounds H2S, (CH3)2S, and SO2

The reactions of iodine monoxide (IO^•) with sulfur-containing compounds, which are important for the atmospheric chemistry, are studied. An attempt is made to distinguish between the heterogeneous and homogeneous reaction pathways. It is shown that, under the experimental conditions, the reactions proceed on the wall and generate iodine atoms into the gas phase. It is found that, at room temperature, the rate constants for the gas-phase reactions of IO^• with (CH₃)₂S and H₂S are lower than 2.5 × 10⁻¹⁴ and 8.0 × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹, respectively; the rate constant for the gas-phase reaction of iodine monoxide with SO₂ ≤ 5.6 × 10⁻¹⁵ cm³ molecule⁻¹ s⁻¹.     

Some Strategies for the Refinement of Disordered Structures with the SHELXL-97 Refinement Program

1 INTRODUCTION finement stage. The person performing the crysta- llographic manipulations works on numerical data The high degree of order in the arrangement of that are quite different from the diffraction images atoms in a crystal is a fundamental characteristic of on a computer terminal, and most often does not even the crystalline state, an ideal crystal being envisaged see the images. to be constructed of regularly-stacked unit cells, each The refinement program, SHELXL-97[1], has …     

Organocatalytic asymmetric domino sulfa-Michael-aldol reactions of 2-mercaptobenzaldehyde with α,β-unsaturated N-acylpyrazoles for the construction of thiochromane

An efficient protocol for the direct construction of bioactive thiochromanes was developed via a catalytic asymmetric cascade sulfa-Michael-aldol reaction of 2-mercaptobenzaldehyde with α,β-unsaturated N-acyl imides. The key to the present methodology is introducing a pyrazole moiety as H-bond acceptor, which allowed for better organization and activation and hence higher enantioselectivity.     

GC–MS Combined with Chemometrics for Analysis of the Components of the Essential Oils of Sweet Potato Leaves

Essential oils from the leaves of two cultivars of sweet potato have been investigated by gas chromatography–mass spectrometry with the help of two chemometric resolution methods, heuristic evolving latent projections and selective ion analysis, and use of temperature-programmed retention indices. The overall volume integration technique was used for quantitative analysis. Eighty-four and forty-five components, accounting for 89.39 and 98.08% of the oils, were tentatively identified in the two cultivars. Thirty-four components were identical in both cultivars. Major constituents of Shuiguo were germacrene D (21.83%), germacrene B (15.17%), caryophyllene (12.44%), and n-hexadecanoic acid (11.24%). Caryophyllene (28.73%), γ-muurolene (13.07%), and β-caryophyllene epoxide (9.04%) were the major components of Xiangshu-17. These results indicate the method is suitable for analysis of the two-dimensional data obtained from essential oils.     

Quantum-chemical modeling of the mechanism for reaction of arenesulfonyl chlorides with α-amino acids

We have calculated the potential energy surface for arenesulfonylation reactions of a-amino acids and glycine hydrates. We have shown that all the reactions occur via a complicated route, with varying angle of attack by the nucleophile according to an S _N2 mechanism. Hydration of glycine lowers the activation energy compared with the gas phase.     

Influence of NO on the Reduction of NO2 with CO over Pt/SiO2 in the Presence of O2

Reduction of NO2 with CO in the presence of NO and excess oxygen, a model mixture for flue gas, over a 0.1% Pt/SiO2 catalyst was studied. The related reaction mechanisms, such as oxidation of CO and NO, were discussed. It was found that there was a narrow temperature window （180-190 ℃） for the reduction of NO2 by CO. When the temperature was lower than the lower limit of the window, the reduction hardly occurred, while when the temperature was higher than the upper limit of the window, the direct oxidation of CO by O2 occurred and thereby NO2 could not be effectively reduced by CO. The presence of NO shifted the window to higher temperatures owing to the inhibition effect of NO on the activation of O2 on Pt, which made it possible to reduce NO2 by CO in flue gas.     

Efficient sulfonylation of ketones with sodium sulfinates for the synthesis of β-keto sulfones

The oxidative sulfonylation of ketones with sodium sulfinates as the sulfone source and DMSO as the oxidant is reported. A series of β-keto sulfones were obtained in good to excellent yields. The advantages of this efficient protocol include the low cost of DMSO and HBr, and a broad scope.