Chiral ligand-controlled catalytic asymmetric epoxidation of α,β-unsaturated carbonyl compounds with peroxide

Asymmetric epoxidation reaction of α,β-unsaturated carbonyl compounds with alkylperoxide was catalyzed by an external chiral tridentate aminodiether-lithium peroxide giving epoxides with good enantiomeric excess. Slow addition of alkylhydroperoxide was beneficial for a catalytic asymmetric reaction. Lone pair electron-differentiating coordination of a carbonyl oxygen to lithium is another critical factor for high enantioselectivity.     

Critical phenomena in ethylbenzene oxidation in acetic acid solution at high cobalt(<Emphasis Type="SmallCaps">II</Emphasis>) concentrations

Critical phenomena in ethylbenzene oxidation in an acetic acid solution at high cobalt(III) concentrations (from 0.01 to 0.2 mol L⁻¹) were studied at 60–90 °C by the gasometric (O₂ absorption), spectrophotometric (Co^III accumulation), and chemiluminescence (relative concentration of radical RO₂ ^·) methods. These phenomena are as follows: (1) increase in the oxidation rate above the theoretical limiting rate of radical autooxidation (k ₃ ²[RH]²/2k ₆); (2) achievement of a maximum and a sharp decrease in the oxidation rate and concentration of radical RO₂ ^· with the further increase in the Co^II concentration (existence of critical concentrations). The oxidation rate increases due to the reaction RO₂ ^· + Co^II + H⁺ → → ROOH + Co^III, while the inhibition effect is caused by the decay of RO₂ ^· radical involving two cobalt(II) atoms: RO₂ ^· + 2 Co^II → R′CO + Co^III + Co^II (k(70 °C) ≈ 300 L² mol⁻² s⁻¹). The detailed scheme (through the formation of the complex RO₂ ^·Co^II) describing the conjugation of these reactions was proposed. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1823–1827, August, 2005.     

醇在钒基催化剂上的氧化

以过氧化叔丁醇作为氧化剂,研究了醇类(苯甲醇、1-苯基乙醇和环己醇)在钒基催化剂上的氧化反应.制备了含苯磷二酚配体或吡嗪-2-羧酸酯配体的钒配合物,并运用傅里叶变换红外光谱、核磁共振谱、紫外-可见光谱及元素分析对其进行了表征.考察了溶剂对该类反应的影响.发现在甲苯溶剂中进行氧化反应时,苯甲醇被氧化成苯甲醛而不会被深度氧化为苯甲酸;而在乙腈溶剂中,苯甲醛和苯甲酸均有生成.此外,对不同钒磷氧化物的催化活性进行了比较,结果表明,在乙腈溶剂中的产品收率比在甲苯溶剂中高.     

Synthesis of novel macrocyclic peroxides by bis(sym-collidine)iodine (I) hexafluorophosphate-mediated cyclization of unsaturated hydroperoxides and unsaturated alcohols

Bis(sym-collidine)iodine (I) hexafluorophosphate-mediated cyclization of unsaturated hydroperoxides, prepared by a variety of different methods, afforded the corresponding 10- to 20-membered macrocyclic peroxides having two or three peroxide units located within one ring in moderate yields. By analogy, cyclization of unsaturated alcohols having one or two peroxide bond in the chain afforded the corresponding cyclic ethers. The efficiency of the latter reactions were found to be a function of the structure of the alcohols.     

间－异丙基甲苯氧化产物的高效液相色谱研究

本文用反相高效液相色谱法（ＨＰＬＣ）分离间－异丙基甲苯氧出产物，采用质谱（Ｍｓ）核磁共振谱（ＮＭＲ）等方法对色谱柱后各流出物作定性鉴定，从而首次建立了用反相液相色谱法测定该氧化产物中的间－异丙基甲苯叔碳氢化过氧化物、间－异丙基甲苯伯碳氢化过氧化物、间－α，α－二甲基甲基苄醇、间－枯茗醇、间－甲基苯乙酮、间－枯茗醛的方法。     

Oxygenation of methane with atmospheric oxygen in aqueous solution promoted by H2O2 and catalyzed by a vanadate ion—pyrazine-2-carboxylic acid system

Methane is oxidized in aqueous solution with atmospheric oxygen and hydrogen peroxide in a reaction catalyzed by a NaVO₃-pyrazine-2-carboxylic acid system. Methyl hydroperoxide is selectively formed at 50°C. The turnover number of the catalyst after 24 h amounts to 480, and the yield of methyl hydroperoxide is 24% with respect to H₂O₂. Formaldehyde and formic acid are mainly formed at 120°C. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1897–1899, October, 1997.     

A new palladium-mediated approach to 4-N-arylamino-1-butanols from peroxidic tetrahydrofuran and primary aromatic amines

Reaction of primary aromatic amines with peroxidic tetrahydrofuran (THF) in the presence of hydrogen and 10% palladium on carbon catalyst results in THF ring opening to give 4-N-arylamino-1-butanols in a good yield. The reaction mechanism is believed to involve a free-radical sequence resulting in an imino alcohol subsequently reduced to product.     

EPR 法研究对氯四苯基锰卟啉对异丙苯过氧化氢的催化分解作用

 以 5,5-二甲基-1-吡咯啉-N-氧化物 (DMPO) 为自旋捕捉剂, 采用电子顺磁共振波谱 (EPR) 法研究了对氯四苯基锰卟啉 (T(p-Cl)PPMnⅢCl) 催化分解异丙苯过氧化氢 (CHP) 的反应过程. 结果表明, 在 25 oC 下的初始反应阶段, 在 T(p-Cl)PPMnⅢCl 与 CHP 的反应体系中仅检测到有异丙苯氧自由基的 DMPO 自旋加合物. 随着 CHP 浓度的增大, 还检测到有异丙苯过氧自由基自旋加合物的重排产物信号. 这说明在 T(p-Cl)PPMnⅢCl 的催化作用下, 初始阶段 CHP 是以 O–O 键均裂的方式产生异丙苯氧自由基引发分解反应, 并主要生成 2-苯基-2-丙醇. 在较大的初始 CHP 浓度下, 异丙苯氧自由基进一步与 CHP 反应, 产生异丙苯过氧自由基. 提出了 CHP 分解反应的主要自由基历程.     

Reaction hazard analysis for cumene hydroperoxide with sodium hydroxide or sulfuric acid

Organic peroxides (OPs) are very susceptible to thermal sources, chemical pollutants or even mechanical shock. Over the years, they have caused many serious explosions. Cumene hydroperoxide (CHP) is widely employed to produce phenol and dicumyl peroxide (DCPO) in the manufacturing process. Differential scanning calorimetry (DSC) and thermal activity monitor (TAM) were employed to determine the potential thermal hazards and thermokinetic parameters (such as exothermic onset temperature (T ₀), maximum temperature (T _max), and enthalpy (ΔH)) of CHP mixed with sodium hydroxide (NaOH) and sulfuric acid (H₂SO₄). High performance liquid chromatography (HPLC) was used to analyze the concentration vs. time of CHP.When CHP is mixed with NaOH, the T ₀ is induced earlier and reactions become more intricate than the pure CHP solution. CHP added to NaOH or H₂SO₄ is more dangerous than pure CHP alone. Depending on the operating conditions, NaOH and H₂SO₄ are the incompatible chemicals for CHP.