Efficient oxidation of alcohols to carbonyl compounds with molecular oxygen catalyzed by N-hydroxyphthalimide combined with a Co species

Highly efficient catalytic oxidation of alcohols with molecular oxygen by N-hydroxyphthalimide (NHPI) combined with a Co species was developed. The oxidation of 2-octanol in the presence of catalytic amounts of NHPI and Co(OAc)2 under atmospheric dioxygen in AcOEt at 70 degrees C gave 2-octanone in 93% yield. The oxidation was significantly enhanced by adding a small amount of benzoic acid to proceed smoothly even at room temperature. Primary alcohols were oxidized by NHPI in the absence of any metal catalyst to form the corresponding carboxylic acids in good yields. In the oxidation of terminal vic-diols such as 1,2-butanediol, carbon-carbon bond cleavage was induced to give one carbon less carboxylic acids such as propionic acid, while internal vic-diols were selectively oxidized to 1,2-diketones.     

Alkenes as ketol surrogates-a new approach toward enantiopure acyloins

[reaction: see text] Enantiopure alpha-hydroxy ketones are important building blocks in organic synthesis. This paper describes the use of cyclic ruthenates for the first catalytic regioselective oxidation of vic-diols to alpha-ketols. The combination of RuCl3/Oxone/NaHCO3 was used in a two-step sequence of asymmetric dihydroxylation and regioselective monooxidation for the synthesis of a broad scope of enantiopure acyloins.     

The RuO4-catalysed dihydroxylation, ketohydroxylation and mono oxidation--novel oxidation reactions for the synthesis of diols and alpha-hydroxy ketones

Alpha-hydroxy ketones are versatile intermediates for the synthesis of complex molecular architectures and subunits of a variety of natural products. Different approaches towards the synthesis of this important functional group combination have been elaborated. The present article summarises our research on the field of RuO4-catalysed oxidations of alkenes that resulted in the development of the first RuO4-catalysed ketohydroxylation of olefins. Mechanistic investigations of both dihydroxylation and ketohydroxylation led to the discovery of the first regioselective catalytic mono oxidation of vic-diols, which was applied in a two-step sequence of asymmetric dihydroxylation and regioselective mono oxidation to furnish enantiopure alpha-hydroxy ketones with both predictable regioselectivity and absolute configuration.     

Mo_2(OAc)_4试剂在邻二醇类结构绝对构型确定中的应用

环状及非环状邻二醇结构的绝对构型的确定是一个令人关注的研究领域.目前国外文献介绍了一种通过使用过渡金属试剂Mo2(OAc)4进行环状及非环状邻二醇结构绝对构型研究的方法,只需将该试剂与溶液中的被测化合物混合即可形成螯合物,无需制备和分离,且立刻可以进行圆二色谱测定,通过诱导产生的一定波长下的Cotton效应与被测化合物的手性中心的关系,可以方便地应用螺旋规则完成绝对构型的研究.将系统地介绍这一方法学,包括对方法学的研究思路、实验步骤、对影响因素的研究结果,以及一些应用的实例.     

Practical method for the absolute configuration assignment of tert/tert 1,2-diols using their complexes with Mo2(OAc)4

We describe here an application of the practical, simple, and reliable approach for the determination of the absolute configuration of sterically demanding tert/tert vic-diols. According to this method, it is only necessary to mix dimolybdenum tetraacteate and a chiral diol in DMSO and record the CD spectra in the 250-650 nm spectral range. From the sign of the CD bands occurring at around 310, 350, and 400 nm, it is possible to establish the chirality of the diol unit expressed by the sign of the O-C-C-O torsion angle. Because the preferred conformation of the diol in the formed complex is known, we are able to determine the absolute configuration of the carbon atoms in the diol subunit even in flexible tert/tert vic-diols.     

Ni/Al2O3催化剂表面状态对CH4氧化反应的影响

采用瞬变响应技术研究了常压700℃条件下气相O2、Ni/Al2O3催化剂表面上可逆吸附氧物种及催化剂的表面状态对CH4吸附、反应以及CH4部分氧化反应的影响,同时也对CH4部分氧化制合成气反应过程中催化剂表面所处的状态进行了研究.结果表明,如果催化剂表面处于氧化态,CH4不能吸附分解,只能通过RidealEley机理与催化剂表面的吸附氧进行非选择性氧化反应,这将严重影响CH4的转化和目的产物H2、CO的选择性.只有在还原的催化剂上,CH4部分氧化制合成气反应才能高转化、高选择性地进行.在CH4部分氧化制合成气反应过程中,催化剂表面处于还原态,不存在多余的中间氧物种NiO,但存在少量的碳物种,这有利于保持催化剂的还原态和抑制CO2的生成.     

Ni/Al~2O~3催化剂上CH~4分解生成的碳物种的转化

本文利用顺序脉冲实验技术,对CH~4在Ni/Al~2O~3催化剂上分解生成的碳物种及其在实验条件下的转化行为进行研究,以探索催化剂上积炭形成的原因。     

Alkane oxidation catalysed by a self-folded multi-iron complex

A preorganised ligand scaffold is capable of coordinating multiple Fe(II) centres to form an electrophilic CH oxidation catalyst. This catalyst oxidises unactivated hydrocarbons including simple, linear alkanes under mild conditions in good yields with selectivity for the oxidation of secondary CH bonds. Control complexes containing a single metal centre are incapable of oxidising unstrained linear hydrocarbons, indicating that participation of multiple centres aids the CH oxidation of challenging substrates.     

乙醇在碳载Pt纳米薄膜电极上吸附和氧化过程研究——II.酸性介质中EQCM和原位FTIR反射光谱

运用电化学循环伏安 ,石英晶体微天平 (EQCM )和原位FTIR反射光谱等方法研究了酸性介质中乙醇在碳载纳米Pt膜电极上吸附和氧化行为 .结果表明 ,乙醇的电氧化与溶液酸碱性及电极表面氧物种有密切的关系 ,并指出乙醇电催化氧化是通过解离吸附产物和反应中间体双途径机理进行的 .在实验条件下 ,经原位FTIR反射光谱检测 ,解离吸附产物为CO ,反应中间体主要有CH3COOH和CH3CHO等物种 .     

乙醇在碳载Pt纳米薄膜电极上吸附氧化过程研究Ⅰ.碱性介质中循环伏安和原位FTIR反射光谱

运用电化学循环伏安法在玻碳载体上制备纳米级厚度的Pt薄膜电极 ,用STM表征电极表面的形貌 ,测定了电沉积层的厚度、表面积和Pt载量 .同时 ,应用电化学循环伏安法和原位FTIR反射光谱研究了乙醇在碱性介质中的吸附和氧化行为 .结果表明 ,乙醇氧化的主要产物是CH3COO- ,仅存在少量乙醛 ,并未观察到任何CO谱峰 .与酸性介质中乙醇氧化的双途径机理不同 ,碱性介质中乙醇氧化未经过解离吸附中间过程     

团聚铂纳米粒子电极在甲醇氧化中的电催化特性

用H2还原法并以Nafion作为稳定剂合成团聚的Pt纳米粒子，附载于玻碳表面制备电催化剂.透射电子显微镜（TEM）和扫描电子显微镜（SEM）表征结果指出,团聚Pt纳米粒子的平均尺寸约为400 nm.运用电化学循环伏安法(CV)和原位傅立叶变换红外反射光谱（in situ FTIRS）研究甲醇的氧化过程，发现团聚Pt纳米粒子电极具有较高的电催化活性.原位FTIRS研究结果检测到甲醇在所制备的电催化剂上氧化的中间体为线型吸附态CO物种，其红外吸收给出异常红外效应的光谱特征.     

Alkane hydroperoxidation with peroxides catalysed by copper complexes

Various copper(I) and copper(II) derivatives, both "simple" ones (copper acetate, perchlorate and a complex with CH3CN) and compounds containing N,O-chelating ligands, catalyse very efficient (turnover numbers attain 2200) oxidation of saturated hydrocarbons with peroxyacetic acid (PAA) or tert-butyl hydroperoxide (TBHP) in acetonitrile solution at 60 degrees C. Alkyl hydroperoxide, alcohol and ketone are formed, the main product being an alkyl hydroperoxide in the oxidation with PAA and an alcohol for the case of TBHP. It has been proposed that the oxidation with PAA is induced via the attack of species r* [HO* or CH3C(=O)O*] on the alkane, RH. A competitive attack of r* on the solvent, CH3CN, also occurs. It has been assumed that in the case of the reaction catalysed by complex Cu(CH3CN)4BF4, copper is present mainly in the form of Cu+ cation, and the rate-limiting step of the oxidation process is the formation of r* via reaction (1): CH3C(=O)OOH + Cu+ --> CH3C(=O)O* + HO- + Cu2+ or/and CH3C(=O)OOH + Cu+ --> CH3C(=O)O- + HO* + Cu2+ with initial rate W1 = k1[PAA][Cu(CH3CN)4BF4] and k1 = 1.7 mol(-1) dm3 s(-1) at 60 degrees C. The activity of the Cu-catalyst is dramatically changed on a small modification of N,O-chelating ligands in the catalyst.     

不同压力下Ni／Al2O3催化剂上CH4部分氧化制合成气反应比较

采用以质谱为检测器的程序升温和瞬变实验技术研究了0．1Mpa和0．7MPa条件下CH4部分氧化制合成气反应,结果表明,与0．1MPa条件下一样,在700度,0．7MPa下CH4可以在金属镍活性中心上迅速分解生成H3和表面NixC,但CH4不能在NiO上分解,也不能被其氧化,CH4的分解,作为在Ni/Al2O3催化剂上进行部分氧化制合成气反应的第一步,是一个体积增大的反应因而加压会抑反应的进行,正是由于在加压条件下CH4的分解受到抑制,才使得在0．7MPa下CH4的转化率明显低于0．1MPa,此外,加压有助于维持催化剂表面处于还原状态,这有利于反应高转化率,高选择性地进行。     

Atmospheric chemistry of a model biodiesel fuel, CH3C(O)O(CH2)2OC(O)CH3: kinetics, mechanisms, and products of Cl atom and OH radical initiated oxidation in the presence and absence of NOx

Relative rate techniques were used to study the kinetics of the reactions of Cl atoms and OH radicals with ethylene glycol diacetate, CH3C(O)O(CH2)2OC(O)CH3, in 700 Torr of N2/O2 diluent at 296 K. The rate constants measured were k(Cl + CH3C(O)O(CH2)2OC(O)CH3) = (5.7 +/- 1.1) x 10(-12) and k(OH + CH3C(O)O(CH2)2OC(O)CH3) = (2.36 +/- 0.34) x 10(-12) cm3 molecule-1 s-1. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the absence of NO in 700 Torr of O2/N2 diluent at 296 K show the primary products to be CH3C(O)OC(O)CH2OC(O)CH3, CH3C(O)OC(O)H, and CH3C(O)OH. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the presence of NO in 700 Torr of O2/N2 diluent at 296 K show the primary products to be CH3C(O)OC(O)H and CH3C(O)OH. The CH3C(O)OCH2O* radical is formed during the Cl atom initiated oxidation of ethylene glycol diacetate, and two loss mechanisms were identified: reaction with O2 to give CH3C(O)OC(O)H and alpha-ester rearrangement to give CH3C(O)OH and HC(O) radicals. The reaction of CH3C(O)OCH2O2* with NO gives chemically activated CH3C(O)OCH2O* radicals which are more likely to undergo decomposition via the alpha-ester rearrangement than CH3C(O)OCH2O* radicals produced in the peroxy radical self-reaction.     

Atmospheric chemistry of CF3CH=CH2 and C4F9CH=CH2: products of the gas-phase reactions with Cl atoms and OH radicals

FTIR-smog chamber techniques were used to study the products of the Cl atom and OH radical initiated oxidation of CF3CH=CH2 in 700 Torr of N2/O2, diluent at 296 K. The Cl atom initiated oxidation of CF3CH=CH2 in 700 Torr of air in the absence of NOx gives CF3C(O)CH2Cl and CF3CHO in yields of 70+/-5% and 6.2+/-0.5%, respectively. Reaction with Cl atoms proceeds via addition to the >C=C< double bond (74+/-4% to the terminal and 26+/-4% to the central carbon atom) and leads to the formation of CF3CH(O)CH2Cl and CF3CHClCH2O radicals. Reaction with O2 and decomposition via C-C bond scission are competing loss mechanisms for CF3CH(O)CH2Cl radicals, kO2/kdiss=(3.8+/-1.8)x10(-18) cm3 molecule-1. The atmospheric fate of CF3CHClCH2O radicals is reaction with O2 to give CF3CHClCHO. The OH radical initiated oxidation of CxF2x+1CH=CH2 (x=1 and 4) in 700 Torr of air in the presence of NOx gives CxF2x+1CHO in a yield of 88+/-9%. Reaction with OH radicals proceeds via addition to the >C=C< double bond leading to the formation of CxF2x+1C(O)HCH2OH and CxF2x+1CHOHCH2O radicals. Decomposition via C-C bond scission is the sole fate of CxF2x+1CH(O)CH2OH and CxF2x+1CH(OH)CH2O radicals. As part of this work a rate constant of k(Cl+CF3C(O)CH2Cl)=(5.63+/-0.66)x10(-14) cm3 molecule-1 s-1 was determined. The results are discussed with respect to previous literature data and the possibility that the atmospheric oxidation of CxF2x+1CH=CH2 contributes to the observed burden of perfluorocarboxylic acids, CxF2x+1COOH, in remote locations.     

低浓度甲烷甲醇深度氧化Ag/La0.6Sr0.4MnO3催化剂

Ag-modified La0.6Sr0.4MnO3 catalysts were prepared and their catalytic performance for deep oxidation of CH4 and CH3OH at low concentrations were investigated. The results showed that the La0.6Sr0.4MnO3 host catalyst with the perovskite-type nano-crystallite structure displayed considerably high catalytic activity for deep oxidation of CH4 and CH3OH at low concentrations. Ag modification to the La0.6Sr0.4MnO3 host catalyst resulted in significant enhancement of the catalyst activity, making the T95 (the reaction temperature needed for conversion of 95%of CH4 or CH3OH) lowered down to 735K (for CH4) and 421K (for CH3OH) from 813 and 465 K over the Ag-free system under the reaction conditions:0.1MPa,CH4/O2/N2=2/12/86(molar ratio),GHSV=45000 h-1 and CH3OH/O2/N2= 0.2/1.0/98.8 (molar ratio),GHSV=58000 h-1,respectively.The carbon containing product was almost CO2 and the contents of HCHO and CO in the reaction exit gas were both under GC detectable limit in both cases.
The results of spectroscopic characterization indicated that modification by proper amount of Ag-dopant did not change the perovskite structure of the La0.6Sr0.4MnO3 host catalyst as a whole. Interaction of Ag-dopant with the surface of the host catalyst,La0.6Sr0.4MnO3,was in favor of high dispersion of the Ag component at the catalyst surface and led to the oxidation of part of the Mn3+species to Mn4+,resulting in an increase of amounts of the reducible Mnn+ species and a decrease of their reduction temperature. On the other hand, this interaction led also to enhancement of adsorption ability of the catalyst toward O2 at relatively low temperature. High activity of the Ag modified La0.6Sr0.4MnO3 catalyst for CH4 and CH3OH complete oxidation was closely related to high redox-activity of the catalyst and its prominent adsorption-activation ability to O2 at relatively low temperatures.     

Oxidative cleavage of vic-diols to aldehydes with dioxygen catalyzed by Ru(PPh3)3Cl2 on active carbon

[reaction: see text] A variety of vic-diols were first successfully cleaved to the corresponding aldehydes with dioxygen catalyzed by Ru(PPh3)3Cl2 on active carbon in fair to good yields. For example, treatment of 1,2-octandiol and 1,2-cyclooctanediol with dioxygen in the presence of Ru(PPh3)3Cl2/C in PhCF3 at 60 degrees C for 15 h produced heptanal and 1,8-octanedial in 77% and 76% yields, respectively.     

低浓度甲烷甲醇深度氧化Ag/La0.6Sr0.4MnO3催化剂

用柠檬酸溶胶－凝胶法制备钙钛矿型Ｌａ０．６Ｓｒ０．４ＭｎＯ３氧化物,并用Ａｇ对其进行修饰,制得Ａｇ／Ｌａ０．６Ｓｒ０．４ＭｎＯ３系列催化剂。结果表明,６％Ａｇ／Ｌａ０．６Ｓｒ０．４ＭｎＯ３催化剂上甲烷或甲醇氧化转化９５％时的反应温度Ｔ９５可低至７３５Ｋ（对ＣＨ４）或４２１Ｋ（对ＣＨ３ＯＨ）;适量Ａｇ的负载修饰并不改变催化剂基质氧化物Ｌａ０．６Ｓｒ０．４ＭｎＯ３的纳米级钙钛矿型结构;Ａｇ的掺杂诱使催     

Density functional theory analysis of the reaction pathway for methane oxidation to acetic acid catalyzed by Pd2+ in sulfuric acid

Density functional theory has been used to investigate the thermodynamics and activation barriers associated with the direct oxidation of methane to acetic acid catalyzed by Pd2+ cation in concentrated sulfuric acid. Pd2+ cations in such solutions are ligated by two bisulfate anions and by one or two molecules of sulfuric acid. Methane oxidation is initiated by the addition of CH4 across one of the Pd-O bonds of a bisulfate ligand to form Pd(HSO4)(CH3)(H2SO4)2. The latter species will react with CO to produce Pd(HSO4)(CH3CO)(H2SO4)2. The most likely path to the final products is found to be via oxidation of Pd(HSO4)(CH3)(H2SO4)2 and Pd(HSO4)(CH3CO)(H2SO4)2 to form Pd(eta2-HSO4)(HSO4)2(CH3)(H2SO4) and Pd(eta2-HSO4)(HSO4)2(CH3CO)(H2SO4), respectively. CH3HSO4 or CH3COHSO4 is then produced by reductive elimination from the latter two species, and CH(3)COOH is then formed by hydrolysis of CH3COHSO4. The loss of Pd2+ from solution to form Pd(0) or Pd-black is predicted to occur via reduction with CO. This process is offset, though, by reoxidation of palladium by either H2SO4 or O2.     

Hydroxyl-radical-initiated oxidation mechanism of bromopropane

Bromopropane has been considered as a replacement for chlorofluorocarbons used as the active component of industrial cleaning solvents, more specifically for HCFC-141b. The proposed mechanism for the atmospheric oxidation of bromopropane is studied via ab initio methodology. Ab initio molecular orbital methods at the CCSD(T)/6-311++G(2df,2p)//MP2/6-31G(d) level of theory have been used to determine the structure and energetics of the 58 species and transition states involved in the atmospheric oxidation of bromopropane. The calculations show that the major oxidation species is bromoacetone. Other brominated species that result from the oxidation are BrCH 2CH 2C(O)H, BrC(O)CH 2CH 3, and BrC(O)H, potential new bromine reservoir species that result from bromopropane in the atmosphere.