Polymer‐supported half‐titanocene catalysts for the syndiospecific polymerization of styrene

Monocyclopendienyltitanium trichloride (CpTiCl₃) was supported on polymer carriers with different hydroxyl contents, and the supported catalysts were used for styrene polymerization. The supported catalysts exhibited high activity even at low Al/Ti ratios and increased the molecular weight of the products, indicating that polymer carriers could stabilize the active sites. The polymers prepared with unsupported and supported catalysts were extracted with boiling n‐butanone and characterized by carbon nuclear magnetic resonance (¹³C NMR) and differential scanning calorimetry. The polymers obtained by supported catalysts had a high fraction of boiling n‐butanone‐insoluble part and high melting temperatures, but ¹³C NMR results showed that syndiotacticity decreased compared with that of polymers prepared with an unsupported catalyst. ESR study on the supported catalysts confirmed that the active sites supported on the carrier dropped into the solution and formed active sites the same as those in the unsupported system when they reacted with methylaluminoxane. ¹³C NMR analysis showed that the polymerization mechanism of the supported active sites was an active‐site controlled mechanism instead of a chain‐end controlled mechanism of the unsupported active sites. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 127–135, 2000     

A Mechanistic Study on the Formation of Dronic Acids

Dronic acid derivatives, important drugs against bone diseases, may be synthesized from the corresponding substituted acetic acid either by reaction with phosphorus trichloride in methanesulfonic acid as the solvent or by using also phosphorous acid as the P-reactant if sulfolane is applied as the medium. The energetics of the two protocols were evaluated by high-level quantum chemical calculations on the formation of fenidronic acid and benzidronic acid. The second option, involving (HO)₂P-O-PCl₂ as the nucleophile, was found to be more favorable over the first variation, comprising Cl₂P-O-SO₂Me as the real reagent, especially for the case of benzidronate.     

Hydrolysis of methyltin(IV) trichloride in aqueous NaCl and NaNO3 solutions at different ionic strengths and temperatures

The hydrolysis of methyltin(IV) trichloride (CH₃SnCl₃) has been studied in aqueous NaCl and NaNO₃ solutions (0 < I/mol dm⁻³ ≤ 1), at different temperatures (15 ≤ T/°C ≤ 45) by­potentiometric measurements (H⁺‐glass electrode). By considering the generic hydrolytic <?tw=97.2%>reaction pCH₃Sn³⁺ + qH₂O = (CH₃Sn)_p(OH)_q^3p−q<?tw>­+ qH⁺ (logβ_pq), we have the formation of five species and logβ₁₂ = −3.36, logβ₁₃ = −8.99, logβ₁₄ = −20.27 and logβ₂₅ = −7.61. The first hydrolysis step is measurable only at very low pH values and was not determined: a rough estimate of the hydrolysis constant is logβ₁₁ = −1.5 (± 0.5). The dependence on ionic strength of logβ_pq is quite different in NaNO₃ and NaCl solutions, and the formation at low pH values of the species CH₃Sn(OH)Cl⁺ has been found with logβ = −1.40. Hydrolysis constants strongly depend on temperature and from the relationships logβ_pq = f(T), ΔH ° values have been calculated. Speciation problems of CH₃Sn³⁺ in aqueous solution are discussed. Copyright © 1999 John Wiley & Sons, Ltd.     

A one-pot synthetic approach to the functionalized isomeric ellipticine derivatives through an imino Diels-Alder reaction

An efficient, three component, one-pot synthesis of new isomeric ellipticine derivatives prepared through an imino Diels-Alder reaction of 3-aminocarbazoles and substituted benzaldehydes with electron-rich alkenes such as 3,4-dihydro-2H-pyran, 2,3- dihydrofuran and ethyl vinyl ether catalyzed by InCl₃ (10 mol %) in ionic liquid is reported. In the case of substituted benzaldehydes, reductive amination is observed.     

Cationic polymerization of dienes VIII: Is the elimination of cross-linking by a bulky electron donor a general behavior in the presence of aluminium trichloride?

Previous works on the polymerization of 1,3-pentadiene initiated by aluminium trichloride in non polar solvent at room temperature in the presence of bulky electron donor (ED) as tri-p-tolylamine have highlighted a stabilization of the polymerizing actives centres by ED, which allowed a reduction of some side reactions and the formation of more precisely defined polypentadienes than ever by cationic polymerization in non polar medium. The aim of this research was to investigate the role of bulky EDs such as tri-p-tolylamine and similar compounds in polar medium in order to obtain if possible a complete control of the polymerization of isoprene and 1,3-pentadiene. The beneficial effect of tri-p-tolylamine was shown in the case of isoprene polymerization at room temperature, with an important reduction of the cross-linked fraction for long reaction times and strong reduction of termination reactions. At −30 °C in the presence of tri-p-tolylamine, polypentadienes more controlled than in non polar solvent could be obtained, with a nearly complete elimination of the cross-linked fraction, while keeping the microstructure approximately constant.     

On the Existence of the Trimer of Gallium Trichloride in the Gaseous Phase

The dependence of the gallium trichloride saturated and unsaturated vapor pressures on temperature was studied by the static method using a quartz membrane zero‐manometer and taking into account the volume of its working chamber and substance mass. Conclusions about the presence of a distinguishable amount of trimeric molecules along with dimeric and momomeric molecules in the vapor were drawn on the basis of the obtained data. The following rough thermodynamic characteristics of a gaseous trimer of gallium trichloride were calculated: Δ_fH° (Ga₃Cl₉, gas, 298 K) = –1466 kJ · mol^–1. S°(Ga₃Cl₉, gas, 298 K) = 654 J · mol^–1 · K^–1. These data were used to elucidate the composition of the gaseous phase at a total pressure of 1 atm in the temperature range of 400–750 K. The suggested existence of trimeric molecules was not contradicted by vibrational spectroscopic analysis of gallium trichloride saturated vapor.     

Reductive Cyclodimerization of α, β‐ Unsaturated Ketones Promoted by AlCl3/Sm System: A Facile Synthesis of 2‐Aroyl‐1,3,4‐triaryl Cyclopentanol Derivatives

Promoted by AlCl₃/Sm bimetallic system, α, β‐unsaturated ketones underwent reductive cyclodimerization to afford cyclopentanol derivatives under mild conditions. The reaction is stereocontrolled and regioselective over the competitive carbon‐carbon double bond reduction.     

气态污染物氯化氰的分光光度法测定

探索了氯化氰（CNCI）气体在不同介质中的稳定性和可吸收性,及光度测定条件,方法用于三聚氯氰工厂烟道气、车间空气及厂区空气中CNCI含量的测定。 结果满意。     

亚磷酸三异丙酯的合成工艺研究

采用三氯化磷、异丙醇为原料,吡啶为有机碱合成亚磷酸三异丙酯.研究了溶剂、反应温度和不同的有机碱对酯产率的影响.在优化的反应条件下,亚磷酸三异丙酯的产率达到85%.对粗品进行减压精馏,产品含量达到95%.     

3-甲基-3-乙酰基-4-乙氧甲酰-环己酮的合成

3-甲基-3-乙酰基-4-乙氧甲酰-环己酮的合成;甲基乙酰基乙氧甲酰环己酮;甲基乙氧甲酰环己烯酮;硝基乙烷;甲基硝基乙基乙氧甲酰环己酮;氟化四丁基铵;三氯化钛