Oxidation of cyclohexane promoted by [Fe(III)(Salen)Cl] and [Mn(III)(Salen)Cl]

Salen complexes of iron(III) and manganese(III) were synthesized and employed as catalysts in the oxidation of cyclohexane, using hydrogen peroxide and tert–butylhydroperoxide. The reactions were carried out in acetonitrile at room temperature. The catalysts were characterized by infrared and Mössbauer spectroscopy, elemental analysis, conductivity and cyclic voltammetry. Conversions up to 10.2% (4.2% and 6.0% yields for cyclohexanol and cyclohexanone, respectively) were obtained for the system [Fe(III)(Salen)Cl]/tBuOOH.     

Epoxidation of alkenes catalyzed by cobalt(II) calix[4]pyrrole

The new developed epoxidation system utilizing cobalt(II) calix[4]pyrrole as a catalyst in the aldehyde/oxygen as an oxidant was explored. Six calix[4]pyrrole ligands were synthesized and the well characterized ligands were complexed with Co(II) salts. It was disclosed that Co(II) meso-tetrakis (4-methoxyphenyl)-tetramethyl calix[4]pyrrole revealed the best catalytic performance to provide the corresponding epoxide in high yields with excellent selectivity under mild conditions. In addition, the stereoselectivity and regioselectivity studies of the system using cis- and trans-stilbenes and 4-vinylcyclohexene, as chemical probes were thoroughly investigated.     

Synthesis and characterization of [Ga(TPP)H] (TPP=tetraphenylporphyrinato)

The synthesis, spectroscopic and structural characterization of the stable gallium hydride compound [Ga(TPP)H] (TPP=5,10,15,20-tetraphenylporphyrinato) have been reported. The hydride compound was synthesized in high yield (85%) by reducing [Ga(TPP)Cl] with sodium borohydride in N,N-dimethylformamide. The title compound was fully characterized by spectroscopic methods (IR, UV–Vis, and ¹H NMR spectroscopy) and its molecular structure was established by X-ray crystallography. The Ga–H IR stretch occurs at 1864 cm⁻¹, and the hydride ¹H NMR resonance locates at −6.47 ppm. The gallium–hydrogen distance is 1.48(4) Å, whereas the gallium atom lies 0.46(1) Å from the perfect porphyrin plane.     

Regioselective olefin arylation catalyzed by [Ir(acac)2Cl]2 with base

By addition of bases to remove Cl in situ, [Ir(acac)₂Cl]₂ was found to work as a catalyst for anti-Markovnikov arylation of olefin with benzene to produce straight-chain alkylbenzene in higher selectivity than the branched alkylbenzene the same as [Ir(acac)₃]₂.     

Oxidation of limonene catalyzed by MnIII(Salen)Cl-H2O

The cationic Mn^III(Salen) complex was proved to be an effective catalyst for the oxidation of limonene with iodosobenzene as terminal oxidant. For reactions conducted in CH₂Cl₂ at rt, with molar ratio of 1 0.05 1 (limonene: catalyst: iodosobenzene) limonene oxidation does occur with an optimal conversion of 60%. The major products according to HRGC-MS and HRGC-IR analyses were cis- and trans-l,2-epoxylimonene (30% and 16.7%, selectivity, respectively), the two diastereoisomers of 1p-menthen-9-al (20% selectivity), and carvone (10% selectivity). A turnover of 60 was observed at 1 0.01 1 ratio. The higher selectivity toward epoxide formation supports the rebound oxygen mechanism.     

Catalytic oxidation of olefins with hydrogen peroxide catalyzed by [Fe(III)(salen)Cl] complex covalently linked to polyoxometalate

The catalytic activity of a hybrid compound [Fe(salen)-POM] (1) consisting of Fe(III)(salen)Cl [H₂salen = N,N′-bis(salicylidene)ethylenediamine] complex covalently linked to a Keggin type polyoxometalate, K₈SiW₁₁O₃₉, (POM) was studied in the oxidation of various olefins in acetonitrile, using hydrogen peroxide as oxygen source. While, [Fe(salen)-POM] catalyst showed moderate to good catalytic activity and product selectivity in the oxidation reactions, the complex Fe(III)(salen)Cl showed poor catalytic activity in these reactions. The effect of other parameters such solvent, oxidant, temperature and the metal type in Schiff base complex were also investigated.     

Epoxidation of Olefins Catalyzed by Mn(II) Salen Complex Anchored on PAMAM–SiO2 Dendrimer

New dendritic catalysts have been prepared by the immobilization of a Mn(II) salen complex on a polyamidoamine dendrimer propagated on the surface of silica. These have been applied in the catalytic epoxidation of olefins. Although the increase of the amount of Mn loading is found to be limited on high-generation dendrimers, the Mn(II) salen complex anchored on the fourth-generation dendrimer shows much higher catalytic activity toward the epoxidation of styrene than that anchored on lower generations. These results suggest that the length of the dendritic backbone chain plays an important role in increasing the accessibility between the catalytic active sites of the immobilized Mn(II) salen complex and the reactant molecules, resulting in the enhancement of the catalytic activity of the Mn(II) salen complex anchored on the fourth-generation dendrimer.     

The Synthesis and Characterization of s-Triazine-Cored and [Fe(III)Salen]-Capped Polymer Complexes

2,4,6-Trichloro-1,3,5-triazine (cyanuric chloride, C₃N₃Cl₃, 1) was used as the starting material. 2-(4-Carboxyphenylamino)-4,6-dichloro-1,3,5-triazine (2) was obtained from the reaction of cyanuric chloride with 4-aminobenzoic acid in the presence of sodium bicarbonate in acetone. A mononuclear complex (4) was obtained by reacting 2 and [FeSalen]₂O (3). A series of polymeric compounds was obtained by reacting 4 with a series of diamines. The polymeric complexes were characterized by elemental analysis, AAS, FT-IR, ¹H NMR, TGA and magnetic susceptibility measurements. The complexes are low-spin, distorted octahedral Fe(III) species that are bridged by carboxylic acids. The [FeSalen]-containing compounds may have the electronic structure t_2g⁵e_g⁰. All the complexes have six coordination and are polymeric.     

Silica Gel Anchored Chiral Mn(III)Salen Complexes for Enantioselective Epoxidation of Unfunctionalised Olefins

Heterogeneous Mn(III) chiral salen complexes are prepared through covalent attachment of salen ligand on silica gel via chloropropyl spacer and subsequent complexation with manganese. The complexes are well characterized by IR, UV/VIS, TGA and elemental analysis. Epoxidation of unfunctionalised prochiral olefins by Mn(III) chiral salen complexes using iodosobenzene and m-CPBA as the terminal oxidants and NMO as a co-oxidant was achieved with good yields albeit low enantiomeric excess.     

凹凸棒粘土负载WO_3催化环戊烯环氧化

以钨酸钠为钨源,凹凸棒粘土(AT)为载体,采用浸渍法制备了凹凸棒粘土负载WO_3(WO_3/AT)催化剂,采用FT-IR和XRD对其进行了表征。以30%H_2O_2为氧源,叔丁醇为溶剂,研究了凹凸棒粘土负载WO_3在环戊烯环氧化反应中的催化性能。结果表明,WO_3与凹凸棒粘土载体中的金属离子(Mg~(2+)、Al~(3+)和Fe~(3+))之间有强的相互作用,形成了M~+—O—W键。反应的最佳工艺条件为:反应温度308 K,反应时间24 h,催化剂用量1.5 g,WO_3负载质量分数40%,催化剂焙烧温度823 K,焙烧时间3 h。在此条件下,环戊烯环氧化物收率为42.2%,环戊烯转化率为96.3%。     

Enantioselective tandem formation and [2,3]-sigmatropic rearrangement of cyclic propargylic oxonium ylides catalyzed by dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate]

This paper describes the first examples of catalyst-dependent asymmetric induction in the periselective [2,3]-sigmatropic rearrangement of propargylic oxonium ylides generated by catalytic diazo decomposition. Catalysis of α-diazo-ß-keto esters 4a—g using dirhodium(II) tetrakis[N-phthaloyl-(S)-tert-leucinate] in toluene has led to the virtually exclusive formation of benzofuran-3-ones bearing an allenic group with up to 79% ee.     

蔗糖在DMF-[BMIm]Cl溶剂中催化制备5-HMF

研究了在N,N-二甲基甲酰胺(DMF)-离子液体[BMIm]Cl混合溶剂中将蔗糖高效转化为5-羟甲基糠醛(5-HMF)的反应。运用紫外-可见分光光度计对水解液中5-HMF进行定量分析并计算其收率。考察了CrCl₃·6H₂O、AlCl₃·6H₂O、SnCl₄·5H₂O、FeCl₃、CoCl₂·6H₂O、ZnCl₂、CuCl₂·2H₂O、CaCl₂ 8种催化剂对反应的催化效果,结果表明AlCl₃·6H₂O催化效果最为明显。以AlCl₃·6H₂O为催化剂研究了不同反应条件如时间、温度、溶剂中DMF-[BMIm]Cl质量比、催化剂AlCl₃·6H₂O的用量对5-HMF收率的影响,得到的最佳条件为以0.5mmol蔗糖为反应物,0.4mmol AlCl₃·6H₂O为催化剂,反应时间2h,反应温度120℃,5g质量比为85:15的DMF-[BMIm]Cl混合溶剂,此条件下5-HMF收率最高可达63.4%。研究表明,DMF-[BMIm]Cl混合溶剂体系对蔗糖转化为5-HMF有一定的促进效果,在此溶剂体系中以AlCl₃·6H₂O为催化剂时可以得到较高的5-HMF产率。     

Binuclear cyano-bridged complex derived from [MnIII(salpn)] and [FeIII(CN)6]: Synthesis,structure and magnetic properties

The reaction of the neutral [Mn(salpn)C(CN)₃(H₂O)] (salpn^2 − = N,N^′-1,3-propylenebis(salicylideneiminato) dianion) with [Fe^III(CN)₆]^3 − in the presence of strong oxidizer (NH₄)₂S₂O₈ yields a binuclear anion complex [NH₃CH₂CH₂CH₂NH₃]^2 +{[Mn^III(salpn)(H₂O)][Fe^III(CN)₆]}^2 − (1). Its structure, DC and AC susceptibility have been studied. Frequency dependence of the AC susceptibility characteristic for single-molecule magnets has been found.     

Brnsted酸型离子液体[Emim]HSO_4催化酯化反应的研究

以吡啶为探针分子,采用红外光谱对合成的离子液体[Emim]HSO4的酸性进行了表征。以[Emim]HSO4离子液体为催化剂研究了乙酸和乙醇的酯化反应。考察了反应温度、反应时间和离子液体／反应物量比对酯化反应的影响．实验得到的优化反应条件为：反应温度40℃,反应时间1h,离子液体：反应物：1：5时,乙酸的转化率为76．73％,乙酸乙酯的选择性为100％。反应后离子液体易于与反应产物分离。     

Hydroxyl Functionalized Methacrylic Terpolymers as Supports for Mn(III) Salen Catalysts and Their Application in Asymmetric Epoxidation

Hydroxyl functionalized gel type resins derived from 2-hydroxyethyl, 2-hydroxypropyl and 2-hydroxy-3-phenoxypropyl methacrylates were applied to covalent immobilization of Mn(salen) complexes via glutarate and carbonate linkers. The obtained catalysts were characterized by FTIR and DR UV–Vis methods and elemental analysis. It was found that the activity of polymeric catalysts obtained in this way depended on both the nature of the functional and cross-linking monomers and the degree of the cross-linking of polymer matrices and the way of complex immobilization. The highest activity was observed for the complexes immobilized on the HEMA resins cross-linked with 3%-mol of diethylene glycol dimethacrylate. For instance, in the presence of the catalysts with (S,S)-salen ligand S-epoxystyrene and (1S, 2R)-epoxyindene could be obtained with 46% and 69% ee, respectively. Attempts have also been made to recycle the selected catalyst. However, a rapid fall off in the activity was observed, although the selectivity was similar in which three cycles.     

Epoxidation of cis-cyclooctene with molecular oxygen catalyzed by magnesium oxide supported polytitazane cobalt (III) complexes

Magnesium oxide supported polytitazane cobalt (III) complex is demonstrated as an effective catalyst for the epoxidation of cis-cyclooctene with molecular oxygen at atmospheric pressure in the presence of isobutyraldehyde as the sacrificial reductant. XPS data show that the high-valent cobalt (III) is stabilized by the multidentate nitrogen ligand of polytitazane. The conversion of cis-cyclooctene is as high as 95.2% with 100% selectivity to the cis-cyclooctene oxide at 25°C within 5 h. The catalyst can be used at least nine times without loss of its activity.     

相转移催化法合成新树型配体——N,N′,N″-(三苄基)-三乙氨基胺和N,N′,N″-(三苯甲酰)-三乙氨基胺

报道了以相转移催化法合成一类新有机试剂——三乙氨基胺类树型配体 N,N′,N″-(三苄基)-三乙氨基胺(TBAA)和N,N′,N″-(三苯甲酰)-三乙氨基胺(TBOAA),产率 85% 以上。此类化合物具有近似三角架形结构,能产生荧光,可以与稀土离子进行选择性配位。     

双水杨醛缩乙二胺合铜[Cu(Salen)]/O2催化氧化安息香

以72.8%的产率合成了双水杨醛缩乙二胺合铜配合物[Cu(Salen)],用正交试验法考察了该配合物对安息香的空气氧化反应的催化作用。实验发现,在水杨醛乙二胺合铜配合物的催化下,安息香经空气氧化生成苯偶酰的产率可达87.9%。     

Kinetic and thermodynamic studies on [Omim]Cl/ZnCl2 catalyzed synthesis of polyoxymethylene dimethyl ethers

Polyoxymethylene dimethyl ethers (OMEs) emerging as green additives for soot emission suppression receive significant attention due to their similar physical properties to diesel. Herein, the transformative pathways of dimethoxymethane (DMM) and trioxane reactions for OMEs production catalyzed by [Omim]Cl/ZnCl₂ having different ZnCl₂ content were demonstrated in combination with the clarification of active species, kinetic and thermodynamic properties, and chemical nature for trioxane decomposition and subsequential formaldehyde insertion steps. The role of [Omim]Cl, which could transform to [Omim]ZnCl₃ or [Omim]Zn₂Cl₅ under different ZnCl₂ content, laid in the formation of active zinc species and promotion of their homogeneity with reactants. The DMM chain growth, which followed the same mechanism and kinetic law, showed kinetic and thermodynamic regimes and had identical equilibrium distribution of OMEs. Only Zn₂Cl₅⁻ species were active for trioxane decomposition, which was the kinetic-relevant step, while both ZnCl₃⁻ and Zn₂Cl₅⁻ were effective for DMM chain elongation.