Efficient Synthesis of Dicycloalkenopyridines： One-pot Multicomponent Condensation of Aldehydes with Cyclic Ketones

Under microwave irradiation, the one-pot multicomponent condensation reaction of three moles of aromatic aldehydes with two moles of cyclic ketones having free α,α'-methylene positions such as cyclopentanone or cyclohexanone in the presence of ammonium acetate and acetic acid afforded dicycloalkenopyridines with two α-arylidene groups in high yields. Under the similar reaction condition, the reaction of aromatic aldehydes with 1-tetralone having only one α-methylene position alternatively resulted in 10-ary...     

The Synthesis of a Series of Phosphoryl Coumarins

Different hydroxy substituted coumarins were successfully phosphorylated with diisopropylphophite （DIPPH） by the Atherton-Todd reaction in 76-89% yields. Moreover, the reaction activities of different hydroxys of the coumarins in the Atherton-Todd reaction were studied.     

Reaction of Alkanesulfinyl Chloride with Grignard Reagents： a Convenient Synthesis of Alkyl Sulfoxides

Alkyl sulfoxides were synthesized in good yields from the reaction of alkanesulfinyl chloride with Grignard reagents in the presence of zinc chloride.     

Unusual Reaction of Diazo Compounds with Enamines

Transition metal catalyzed decomposition of diazo compounds and consequent transformations constitute various synthetic useful reactions in the past decades. The catalytic addition of diazo compounds to olefins generally provides cyclopropanes in high yield. However the reaction of electron-rich enamines with diazo compounds gave variable results. Wenkert et al. reported the reaction of enamines with ethyl diazoacetae (EDA) in the presence of cuprous chloride or silver oxide unexpectedly gave…     

Production of Superoxide Ion with Carbon Gas-Diffusion-Electrode And Reaction of Superoxide Ion with Aromatic Halide

Superoxide ion O~-_2 is prepared in aprotic media by carbon gas-diffusion-electrode for the first time. The experimental results indicate that this electrode is superior to carbon plane-electrode in the reaction of O~-_2 with p-bromonitrobenzene. When the gas-diffussion-electrode is used, the yield of the product nitrophenol increases by 20%, and the selectivity of the reaction is nearly doubled as compared with the plane-electrode.     

Free radical mediated bromization of methylenecyclopropanes: Preparation of 2,4-dibromobutenes without transition metal

A series of 2,4-dibromobutenes were synthesized by the reaction of methylenecyclopropanes with KBr in HOAc in the presence of dibenzoyl peroxide, providing an environment friendly method for the synthesis of 2,4-dibromobutenes.     

Synthesis of 5-Fluoroalkyl Isoxazolidines via 1,3-Dipolar Cycloaddition of Ethyl 2-Hydropolyfluoroalk-2-enoates with Nitrones

1,3-Dipolar cycloaddition reactions of ethyl 2-hydropolyfluoroalk-2-enoates (1) with some nitrones were described. The reaction of 3,4-dihydroisoquinoline N-oxide (2) with 1 took place readily in methylene chloride at room temperature to give the corresponding 5-fluoroalkylisoxazolidines regioselectively as a mixture of two diastereoisomers (trans and cis) in high yields, while longer reaction time and higher temperature were needed in the case of non-cyclic nitrones. Under similar conditions the reaction of quinoline N-oxide (14) with 1 did not give the expected adducts and a ring-opening product was obtained.     

Studies of Unusual Oxidation States of Transition Metals Ⅱ——Kinetics and Mechanism of Oxidation of Pyruvate by Diperiodatoargentate (Ⅲ)Ion

The kinetics of oxidation of pyruvate by diperiodatoargentate( III) ion (DPA) has been studied spec-trophotometrically in alkaline medium. It was found that the reaction order with respect to both DPA and pyruvate is unity and the rate equation can be expressed asThe rate increases with the increase in [OH ] and decreases with the increase in [periodate]. There is a positive ionic strength effect in this reaction system. A mechanism has been proposed to explain the experimental results. The observed activation parameters are presented.     

Coupling Reaction of Organoboronic Acids with Chloropyrimidines and Trichlorotriazine

Pd-catalyzed cross-coupling reactions of chloropyrimidirtes with alkenylboronic acids readily proceed to give the corresponding alkenylpyrimidines in high to excellent yields. The coupling reaction of 2,4-dichloropyrimidine or 2,4,6-trichloropyrimidine with one equivalent of alkenylboronic acid occurred more easily on 4-position than on 2-position, which implied that the reaction is highly regioselective. The reaction is stereospecific since the configuration of C=C remained intact. The preliminary study on the cross-coupling reactions of 2,4,6-trichlorotriazine with one equivalent of arylboronic acids showed that the reactions afforded the monosubstituted triazines in moderate yields. The effect of steric hindrance of the substitutents on the reactions was found.     

Iodine-mediated regioselective hydroxyselenenylation of alkenes:Facile access to β-hydroxy selenides

In the presence of molecular iodine, the reaction of alkenes with diselenides proceeds efficiently under mild reaction conditions in MeCN/H₂O, which affording β-hydroxy selenides with high regioselectivity and in good to excellent yields.     

Ab initio Mechanism Study on the Reaction of Chlorine Atom with Formic Acid

The potential energy surface(PES) for the reaction of Cl atom with HCOOH is predicted using ab initio molecular orbital calculation methods at UQCIDS(T,full)6-311 G(3df,2p)//UMP2(full)/6-311 G(d,P) level of theory with zero-point vibrational energy (ZPVE) correction.The calculated results show that the reaction mechanism of Cl atom with formic acid is a C-site hydrogen abstraction reaction from cis-HOC(H)O molecule by Cl atom with a 3.73kJ/mol reaction barrier height,leading to the formation of cis-HOCO radical which will reacts with Cl atom or other molecules in such a reaction system.Because the reaction barrier height of O-site hydrogen abstraction reaction from cis-HOC(H)O molecule by Cl atom which leads to the formation of HCO2 radical is 67.95kJ/mol,it is a secondary reaction channel in experiment,This is in good agreement with the prediction based on the previous experiments.     

The Ring-Chain Competition in Nonlinear Polycondensation (Ⅱ)——The Intramolecular Reaction Equations of the System Containing Two Dynamic Parameters

Flory considered that the discrepancy between classical gelation theory and real reaction system was mainly attributed to the intramolecular reaction.On the basic principles of the probability we analysed the growing-disappearing of the groups in the even generations against a certain group statistically when three different reaction systems containing two dynamic parameters reached some degree of reaction.Furthermore,we obtained the intramolecular reaction equations in the form of analysis by means of introducing probability factor of cyclization bond.Using the equations obtained from this paper to deal with the critical condition of gelation,we found that the theoretical values agreed with the experimental ones.     

The reaction of perfluoroalkanesulfonyl halides Ⅶ. Preparation and reactions of trifluoromethanesulfonyl bromide

The reaction between sodium trifluoromethanesulfinate, which was prepared from trifluorome-thyl bromide, with bromine in aqueous solution resulted in the formation of trifluoromethanesulfonylbromide (CF_3SO_2Br). CF_3SO_2Br reacted with alkenes and alkyne to give the corresponding adductswith the loss of SO_2 in good yields, and with compounds containing active hydrogen to give brominatedderivatives. A radical reaction mechanism was proposed and confirmed by EPR study.     

Exact quantum and TST-CEQ study of the collinear reaction O+HCl

Exact quantum calculations of reaction probabilities have been carried out using hyperspherical coordinates for the collinearr reaction O+HCl(v <1) -OH(v'<1)+Cl . A generalized LEPS potential energy surface with a barrier height of 8.12 kcal/mol has been used in the calculations. According to the calculated results we found that (1) the reaction probability oscillates with energy, (2) the reaction probability shows vibrational adiabaticity, although it is poorer than that for symmetric reaction Cl + HC1. The analysis of resonance has also been done. The reaction rate constants and average cross sections have been calculated by TST-CEQ method. The rate constants are in agreement with that by QCT and smaller than the experimental one. Finally, the threshold has been estimated and is in good agreement with that of the literature.     

Preparation of p—1,1,3,3—Tetramethylbutylphenol by Using Nafion—H Catalyst

p-1,1,3,3-Tetramethylbutylphenol was prepared by the alkylation of the phenol with Nafion catalyst in extremely high yield. Various reaction conditions were investigated, including the reaction temperature,reaction time, ratio of the starting material, amount of the Nafion catalyst and the recycle times of the catalyst.     

Addition Mechanisms of Phenol toward Formaldehyde under Acidic Condition： a Theoretical Investigation

The reaction mechanisms of phenol with formaldehyde in the first and second addition at the ortho- and para-position in acid solution were theoretically investigated at the PW91/DNP level with solvent effects included. The reaction of phenol with protonated methanediol firstly forms an adduct intermediate, via a SN2 mechanism with a water molecule as the leaving group. From the adduct intermediate, there are two reaction channels involving a proton transfer to form the addition products. One is that a proton directly transfers via a four-membered ring transition state with a notable energy barrier (Four-member mechanism). Another mechanism involving a water molecule as catalyst to mediate the proton transfer (WCP mechanism), is a barrierless process, indicating that the formation of the adduct intermediate, the first reaction step, is rate-limiting. The reaction products are free hydroxymethyl phenols and/or hydroxybenzy carbocation (HOC6H4CH2+) which plays an important role in the following formation of methylene and methylene ether linkages. The second addition reactions between formaldehyde and hydroxymethyl phenol at all possible reaction sites of the phenol ring in acid solution were also investigated and discussed.     

Chemical Modification of Tryptophan Residues in Pullulanase

Tryptophan（Trp）residues in pullulanase have been chemically modified with N-bromossuccinimide（NBS）. The results of ultraviolet spectra indicated that there are 18 Trp residues in pullulanase and nine of them are located on the surface of the enzyme. Three of these Trp residues are none-essential residues which showed the fastest reaction speed by Zhou＇s plot. Two of the seven relative faster reacting residues are essential for the activity of the enzyme. The other eight are none-reactive residues with lowest reaction speed.     

Chemical Reactions and Kinetics of the Carbon Monoxide Coupling in the Presence of Hydrogen

The chemical reactions and kinetics of the catalytic coupling reaction of carbon monoxide to diethyl oxalate were studied in the presence of hydrogen over a supported palladium catalyst in the gaseous phase at the typical coupling reaction conditions. The experiments were performed in a continuous flow fixed-bed reactor. The results indicated that hydrogen only reacts with ethyl nitrite to form ethanol, and kinetic studies revealed that the rate-determining step is the surface reaction of adsorbed hydrogen and the ethoxy radical (EtO-). A kinetic model is proposed and a comparison of the observed and calculated conversions showed that the rate expressions are of rather high confidence.     

Theoretical Study on the Reaction Mechanism of Ketene CH2CO with Isocyanate NCO Radical

The bimolecular single collision reaction potential energy surface of an isocyanate NCO radical with a ketene CH2CO molecule was investigated by means of B3LYP and QCISD（T） methods. The computed results indicate that two possible reaction channels exist on the surface. One is an addition-elimination reaction process, in which the CH2CO molecule is attacked by the nitrogen atom at its methylene carbon atom to lead to the formation of the intermediate OCNCH2CO followed by a C-C rupture channel to the products CH2NCO＋CO. The other is a direct hydrogen abstraction channel from CHzCO by the NCO radical to afford the products HCCO＋HNCO. Because of a higher barrier in the hydrogen abstraction reaction than in the addition-elimination reaction, the direct hydrogen abstraction pathway can only be considered as a secondary reaction channel in the reaction kinetics of NCO＋ CH2CO. The predicted results are in good agreement with previous experimental and theoretical investigations.     

Kinetics of the Oxidative Dehydrogenation of Propane over a VMgO Catalyst

The reaction kinetics of the oxidative dehydrogenation of propane was studied at 475-550℃ over a VMgO catalyst. Vanadium-magnesium-oxides are among the most selective and active catalysts for the dehydrogenation of propane to propylene. Selectivity to propylene up to about 60% was obtained at 10% conversion, but the selectivity decreased with increasing conversion. No oxygenates were detected, the only by-products were CO and CO2. The reaction rate of propane was found to be first order in propane and close to zero order in oxygen, which is in agreement with a Mars van Krevelen mechanism with the activation of the hydrocarbon as the rate determining step. The activation energy of the conversion of propane was found to be 122±6 kJ/mol.