A Highly Stereoselective Synthesis of 2－Carbomethoxy－3－aryl－4－carboethoxy－5－methyl－cis－2，3－dihydrofurans

ＡＨｉｇｈｌｙＳｔｅｒｅｏｓｅｌｅｃｔｉｖｅＳｙｎｔｈｅｓｉｓｏｆ２－Ｃａｒｂｏｍｅｔｈｏｘｙ－３－ａｒｙｌ－４－ｃａｒｂｏｅｔｈｏｘｙ－５－ｍｅｔｈｙｌ－ｃｉｓ－２，３－ｄｉｈｙｄｒｏｆｕｒａｎｓＤＩＮＧＷｅｉ－ｙｕ；ＣＨＥＮＹａ－ｌｉ；ＺＨＡＮＧ...     

STUDIES ON THE SYNTHESIS OF SESAMIN－GROUP LIGNANS V． A CONVENIENT METHOD FOR THE PREPARATION OF 2－ARYL－4－PHENYLOXAZOLES

ＳＴＵＤＩＥＳＯＮＴＨＥＳＹＮＴＨＥＳＩＳＯＦＳＥＳＡＭＩＮ－ＧＲＯＵＰＬＩＧＮＡＮＳＶ．ＡＣＯＮＶＥＮＩＥＮＴＭＥＴＨＯＤＦＯＲＴＨＥＰＲＥＰＡＲＡＴＩＯＮＯＦ２－ＡＲＹＬ－４－ＰＨＥＮＹＬＯＸＡＺＯＬＥＳ￥Ｃｏｒｒｅｓｐｏｎｄｅｎｔａｕｔｈｏｒ．２－ａｒｙｌ－４－ｐｈｅｎｙｌｏｘａｚｏｌｅｓ．Ｔｈｅｏｔｈｅｒｏｌｌｅｂｙｔｈｅｒｅａｃｔｉｏｎｏｆａ－ｍｅｔｈｙｌｐｈｅｎａｃｙｌｂｅｎｚｏａｔｅｗｉｔｈａｍｍｏｎｉｕｍａｃｅｔａｔｅｉｎｂｏｉｌｉｎｇａｃｅｔｉｃａｃｉｄｔｏｆｏｒｍａｆｕｔｕｒｅｏｆ２，４－ｄｉｐｈｅｎｙｌ－５ｍｅｔｈｙｌｏｘａｚｏｌｅａｎｄ２，４－ｄｉｐｈｅｎｙｌ－５－ｒｎｅｔｈｙｌｉｎｄｄａｚｏｌｅｂｏｔｈｉｎａｂｏｕｔ４０％ｙｉｅｌｄ，ｈｉｌｔｔｉｌｌｓｍｅｔｈｏｄｉｓａｐｐｌｉｃａｂｌｅｆｏｒｔｈｅｐｒｅｐａｒａｔｉｏｎｏｆ２－ａｒｙｌ－４－ｐｈｅｎｙｌｏｘａｚｏｌｅｓ．Ｂｙａｎａｌｏｇｙ，ｐｌｉｅｎａｃｙｌｂｅｎｚｏａｔｅｉｓａｌｌｏａｌｌｏｗｅｄｔｏｒｅａｃｔｗｉｔｈａｌｎｍｏｎｉｌｌｍａｃｅｔａｔｅｉｎｂｏｉｌｉｎｇａｃｅｔｉｃａｃｉｄ．Ａｍｉｘｔｕｒｅｏｆ２，４－ｄｉｐｈ     

Study on the Total Synthesis of Hainanolide－Construction of Tricyclic Intermediate（I）

ＳｔｕｄｙｏｎｔｈｅＴｏｔａｌＳｙｎｔｈｅｓｉｓｏｆＨａｉｎａｎｏｌｉｄｅ－ＣｏｎｓｔｒｕｃｔｉｏｎｏｆＴｒｉｃｙｃｌｉｃＩｎｔｅｒｍｅｄｉａｔｅ（Ｉ）ＬｕＹａｎＺＨＡＮＧ；ＳｈｉＺｈｉＣＨＥＮ；ＤｏｎｇＷＥＩ；ＬｉａｎｇＨＵＡＮＧ；ＪｉＪｉｅＣＨＡ...     

The Difference of Electronic Properties and the Effect of Hydrogen－bondofcis－and trans－Polyazomethine

ＴｈｅＤｉｆｆｅｒｅｎｃｅｏｆＥｌｅｃｔｒｏｎｉｃＰｒｏｐｅｒｔｉｅｓａｎｄｔｈｅＥｆｆｅｃｔｏｆＨｙｄｒｏｇｅｎ－ｂｏｎｄｏｆｃｉｓ－ａｎｄｔｒａｎｓ－ＰｏｌｙａｚｏｍｅｔｈｉｎｅＷＡＮＧＲｏｎｇ－ｓｈｕｎ，ＰＡＮＸｉｕ－ｍｅｉａｎｄＳＵＺｈｏｎｇ...     

Researches into the Proton Conductivity of Molybdovanadophosphoric Acids with Wells－Dawson Structure

ＲｅｓｅａｒｃｈｅｓｉｎｔｏｔｈｅＰｒｏｔｏｎＣｏｎｄｕｃｔｉｖｉｔｙｏｆＭｏｌｙｂｄｏｖａｎａｄｏｐｈｏｓｐｈｏｒｉｃＡｃｉｄｓｗｉｔｈＷｅｌｌｓ－ＤａｗｓｏｎＳｔｒｕｃｔｕｒｅＷＡＮＧＥｎ－ｂｏ；ＬＩＢａｉ－ｔａｏ；ＷＡＮＧＺｕｏ－ｐｉｎｇａｎｄ...     

Direct Electron－transfer Reaction of Cytochrome C at a Bare Spectrographic Graphite Electrode

ＤｉｒｅｃｔＥｌｅｃｔｒｏｎ－ｔｒａｎｓｆｅｒＲｅａｃｔｉｏｎｏｆＣｙｔｏｃｈｒｏｍｅＣａｔａＢａｒｅＳｐｅｃｔｒｏｇｒａｐｈｉｃＧｒａｐｈｉｔｅＥｌｅｃｔｒｏｄｅＹＵＡｉ－ｍｉｎ，ＣＨＥＮＨｏｎｇ－ｙｕａｎａｎｄＨＡＮＪｉ－ｌｉｎ（Ｄｅｐａｒｔｍｅ...     

Detection of Catecholic Compounds with Field-ampilfied CZE-Amperometry

ＤｅｔｅｃｔｉｏｎｏｆＣａｔｅｃｈｏｌｉｃＣｏｍｐｏｕｎｄｓｗｉｔｈＦｉｅｌｄ－ａｍｐｉｌｆｉｅｄＣＺＥ－ＡｍｐｅｒｏｍｅｔｒｙＨＵＳｈｅｎ,ＰＡＮＧＤａｉ－ｗｅｎ,ＨＵＹｏｎｇ－ｇａｎｇ,ＣＨＥＮＧＪｉｅ－ｋｅ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓ...     

Formation of Dithymidylic Acid by Ester Exchange Reaction on－Phosphoryl Serine

ＦｏｒｍａｔｉｏｎｏｆＤｉｔｈｙｍｉｄｙｌｉｃＡｃｉｄｂｙＥｓｔｅｒＥｘｃｈａｎｇｅＲｅａｃｔｉｏｎｏｎ－ＰｈｏｓｐｈｏｒｙｌＳｅｒｉｎｅＹｕａｎＭＡ；ＸｉａｎｇＨｏｎｇＬＩ；ＹｉＣＨＥＮ；ＹｕＰｉｎｇＦＥＮＧ；ＹｕＦｅｎＺＨＡＯ（Ｄｅｐａｒｔｍｅｎ...     

STUDIES ON MACROCYCLIC DITERPENOIDS（XI）──A Convergent and Stereoselective Synthesis of Cembrenene Precursor－4，10－Dimethyl－7－Isopropenyl－14－Oxo－3Z，5E，10E－Pentadecatrienal

ＳＴＵＤＩＥＳ　ＯＮ　ＭＡＣＲＯＣＹＣＬＩＣ　ＤＩＴＥＲＰＥＮＯＩＤＳ（ＸＩ）──Ａ　Ｃｏｎｖｅｒｇｅｎｔ　ａｎｄ　Ｓｔｅｒｅｏｓｅｌｅｃｔｉｖｅ　Ｓｙｎｔｈｅｓｉｓ　ｏｆ　Ｃｅｍｂｒｅｎｅｎｅ　Ｐｒｅｃｕｒｓｏｒ－４，１０－Ｄｉｍｅｔｈｙｌ－７－Ｉ...     

Electric Anisotropy and Two－dimensional Energy Band of Undoped and Heavily Doped Polyacetylene

ＥｌｅｃｔｒｉｃＡｎｉｓｏｔｒｏｐｙａｎｄＴｗｏ－ｄｉｍｅｎｓｉｏｎａｌＥｎｅｒｇｙＢａｎｄｏｆＵｎｄｏｐｅｄａｎｄＨｅａｖｉｌｙＤｏｐｅｄＰｏｌｙａｃｅｔｙｌｅｎｅＨＵＡＮＧＺｏｎｇ－ｌｉａｏ，ＷＡＮＧＸｉｕ－ｊｕｎ，ＴＯＮＧＬａ－ｇａ，ＬＩＢａｉ...     

STUDIES ON THE INITIATION MECHANISM OF CERIC ION AND ACETYLACETONE REDOX SYSTEM IN VINYL POLYMERIZATION

The initiation mechanism of acrylamide (AAM)polymerization using ceric ion/acetylacetone system as an initiator has been studied. The redox polymerization was revealed by the low value of overall activation energy of AAm polymerization. The structure of free radicals formed from above-mentioned initiation sytem were detected by radical trapping and ESR spectra techniques and the end groups of polymers obtained were determined by FT-IR spectra analysis method. Based on these results the initiation mechanism is proposed.     

Polymerization of acrylamide with ceric ion–malic acid redox pair

The polymerization of acrylamide (M) in aqueous sulfuric acid medium initiated with ceric ammonium sulfate–malic acid redox pair was investigated at 35 ± 0.2°C under nitrogen atmosphere. The initiation was caused by the free radical generated by the decomposition of the complex formed between ceric ion and malic acid (MA). The rate of monomer disappearance was proportional to the first power of malic acid, ceric ion, and monomer concentrations at lower ceric ion concentrations. However, at higher ceric ion concentrations the rate was independent of [Ce(IV)]. The rate of ceric ion disappearance was proportional to [MA] and [Ce(IV)] but independent of [M] at lower ceric ion concentrations. The activation energy was found to be 57.74 kJ/mol. Sulfuric acid retarded the reaction. Molecular weights increased with increasing [M] and decreasing [Ce(IV)].     

Polymerization of Methacrylamide Initiated by Ceric Ion-Citric Acid Redox System

Homogeneous polymerization of methacrylamide initiated by the ceric ammonium sulfate-citric acid (CA) redox pair has been investigated and reported at 35 ± 0.2°C under nitrogen atmosphere. The initiation was caused by the free radical generated by the decomposition of the complex formed between ceric ion and citric acid. The rate of monomer disappearance was found to be proportional to [CA]^0.4, [Ce^0.4+]^0.65, and [Monomer]¹ The rate of ceric ion disappearance was directly proportional to the ceric ion concentration but independent of the monomer concentration. The initial rate was independent of [H₂SO₄]. The activation energy of the system was found to be 21.4 kJ/mol.     

Studies on the kinetics of ceric-thiourea initiated aqueous polymerization of methyl methacrylate—II. Mechanistic features in strongly acid solutions

The kinetics of ceric-thiourea initiated aqueous polymerization of methyl methacrylate in 1 M H₂SO₄ have been studied. Ceric ion and thiourea initially form an 1:1 complex which then reacts with uncomplexed ceric ion to form the initiating thiocarbamido radicals. The termination is predominantly biomolecular below an initial ceric concentration of 0.66 × 10^?2 M (depending upon the rate of initiation). At higher initial ceric concentrations, polymer radicals are terminated overwhelmingly by ceric ions. Substituted thioureas reduce the rate of polymerization according to the order of increasing electron density on the sulphur atom. The overall activation energy of polymerization is 12.1 kcal/mol in the region of bimolecular termination and 10.2 kcal/mol in the region of metal ion termination.     

Effect of amines on the ceric ion-initiated polymerization of vinyl monomers. I. Polymerization of acrylonitrile by ceric ion–triethylamine catalyst system

The polymerization of acrylonitrile was studied in aqueous solution with ceric ammonium sulfate in the presence of triethylamine as initiator at 30, 40, and 50°C. The rate of polymerization was found to be linear with the concentration of the amine and independent of ceric ion concentration. A reaction scheme involving initial complex formation between ceric ion and the amine and subsequent disproportionation of the conplex to produce free radicals is proposed for the initiation reaction. The termination step is postulated as involving oxidation of the polymer chains by ceric ions. The results have been explained in the light of the proposed reaction scheme.     

Coordinated radical polymerization and redox polymerization of acrylamide by ceric ammonium nitrate

The ceric salt-initiated polymerization on acrylamide and graft copolymerization of acrylamide onto cellulose were studied. The mechanism of the ceric salt-initiated polymerization of acrylamide in the homopolymerization system can be explained by a radical mechanism based upon Ce⁴⁺-coordinated acrylamide, and the mechanism of the ceric salt-initiated graft copolymerization of acrylamide onto cellulose can be explained in two ways: a free-radical mechanism with the ceric—cerous redox system, and a radical mechanism based upon Ce⁴⁺-coordinated acrylamide. The velocities of initiation, propagation, and termination in the redox mechanism are quite different from those in the coordinated radical mechanism. From the infrared absorption and nuclear magnetic resonance spectra measurements it is concluded that the structure of the ceric-coordinated acrylamide is the π-complex.     

VINYL RADICAL POLYMERIZATION INITIATED WITH CERIC ION AND N-(SUBSTITUTED PHENYL) ACETAMIDE SYSTEMS

The polymerization of acrylamide (AAM)in H_2O/DMF or in H_2O/CH_3CN mixed solvent initiated with ceric ion (Ce~(4+) )/N-(substituted phenyl)-acetamide systems have been studied. The redox polymerization was revealed by the low value of overall activation energy (E_α) of AAM polymerization using ceric ion/N-(substituted phenyl) acetamide system as an initiator. The end group of polymer formed was detected by IR spectrum analysis method, it revealed the presence of N-(m-acetoxy-methylphenyl) acetamide (m-AAe) moiety end group in the polymer obtained with ceric ion/m-AAe initiation system.     

Polymerization of Acrylonitrile with Ceric lon-2-Propanethiol as Initiator System

The kinetics of the polymerization of arylonitrile with ceric ammonium sulfate in the presence of 2-propanethiol as the redox initiator system in aqueous solution has been investigated. The rate of polymerization was found to be proportional to the square root of both ceric ion and thiol concentrations, and the monomer exponent was close to 1.5. Spectral studies indicated that there is a complex formation between ceric ion and the monomer acrylonitrile. A kinetic scheme, based on initial formation of this complex and its subsequent reaction with the thiol to produce the free radicals (RS.) responsible for initiation has been postulated to account for the observed results. The activation energy and different kinetic and transfer constants for the system have also been evaluated.     

Effects of metal salts on polymerization. Part IV. Polymerization of N-vinylcarbazole initiated by oxidizing metal nitrates

The polymerization of N-vinylcarbazole (VCZ) in ethylene dichloride, acetone, benzene, and dioxane with cupric nitrate, ferric nitrate, and ceric ammonium nitrate as catalyst was studied. In all cases the polymerization seemed to be of a cationic nature, judged by copolymerization with styrene. Electron spin resonance (ESR) spectroscopy was made for the polymerization system and also for a system containing N-ethylcarbazole instead of VCZ. Singlet ESR spectra were observed for all systems containing ceric salt and for some systems containing ferric salt but not for systems containing cupric salt. The ESR spectra indicated the formation of an ion radical by electron transfer between the oxidizing metal salt and the carbazole derivatives. Mechanisms of initiation other than electron transfer were less likely, and it was concluded that the initiation process was most likely to be of the electron transfer type.     

Aqueous polymerization of methyl methacrylate initiated by the redox system Ce(IV)–isopropyl alcohol. Kinetics and molecular weight

Polymerization of methyl methacrylate was carried out in aqueous nitric acid in the temperature range 26–40°C, with the redox initiator system ceric ammonium nitrate–isopropyl alcohol. A short induction period was observed, as well as the attainment of a limiting conversion, and the total ceric ion consumption with reaction time. The reaction orders were 1/2 and 3/2 with respect to the IPA and monomer concentration, respectively, within the range (3–5) × 10^?3M of Ce(IV). But at lower Ce(IV) concentration (≤ 1 × 10^?3M), the order with respect to monomer and Ce(IV) changed to 1 and 1/2, respectively. The rate of ceric ion disappearance was first order with respect to Ce(IV) concentration and (R_Ce)^?1 was proportional to [IPA]^?1. Both the rate of polymerization and the rate of ceric ion consumption increase with rise in temperature. The average-molecular weight can be controlled by variations in IPA, Ce(IV), and monomer concentrations, and in temperature. A kinetic scheme involving oxidation of IPA by Ce(IV) via complex formation, whose decomposition gives rise to a primary radical, initiation, propagation, and termination of the polymeric radicals by bimolecular interaction is proposed. An oxidative termination of primary radicals by Ce(IV) is also included.