手性salen(Mn)催化烯烃不对称环氧化反应的研究进展

烯烃的不对称环氧化物通过选择性开环或者官能团的转化,可以生成一系列有价值的手性化合物,被广泛用作医药、农药、香料等精细化学品的合成中间体.手性Mn(salen)金属配合物被证明是烯烃不对称环氧化最有效的催化剂之一.本文综述了近年来均相手性Mn(salen)催化剂、有机聚合物固载的手性Mn(salen)、无机载体固载手性...     

Silica-supported cobalt(II) tetrasulfophthalocyanine catalyzed aerobic oxidation of thiols to disulfides under neutral conditions

A very simple and mild reaction is described for the aerobic oxidative coupling of thiols to disulfides by silica-supported cobalt(II) tetrasulfophthalocyanine as the catalyst in non-aqueous media under neutral conditions at room temperature. The catalyst can be reused for the oxidative coupling of several thiols without any significant loss of catalytic activity. Correspondence: Ahmad Shaabani, Department of Chemistry, Shahid Beheshti University, P.O. Box 19396, 4716 Tehran, Iran.     

Enantioselective epoxidation of nonfunctionalized alkenes catalyzed by recyclable new homochiral bis-diamine-bridged bi-Mn(salen) complexes

Three new homochiral bis-diamine-bridged bi-Mn(salen) complexes were synthesized. Their catalysis on asymmetric epoxidation of α-methylstyrene, styrene and indene was studied with NaClO and m-CPBA as oxidants respectively. This homogeneous catalyst exhibited comparable catalytic activity and enantioselectivity to the Jacobsen’s catalyst in the asymmetric epoxidation of unfunctionalized olefins. Furthermore, the catalyst could be conveniently recovered and reused at least five times without significant losses of both activity and enantioselectivity. Specially, it also could be efficiently used in large-scale reactions with superior catalytic disposition being maintained at the same level, which provided the potential for the applications in industry. The effect of axial bases, temperature and solvent on activity and enantioselectivity of the catalytic system were also studied.     

Ring-opening of unsymmetrical 1,2-dioxines using cobalt(II) salen complexes

The regioselectivity of the metal-catalyzed ring opening of unsymmetrical 1,2-dioxines to cis-gamma-hydroxyenones was investigated using two different Co(II) salen complexes. Regioselectivity was determined by direct examination of the enone ratios and by derivitization with a stabilized phosphorus ylide. The steric influence of the substituents on the 1,2-dioxine was the primary influence on regioselectivity. Temperature played little role; however, solvent and selection of Co(II) complex could be used to mildly influence the outcome of the rearrangement for selected substrates. The origins of the selectivity for the reaction are discussed.     

Asymmetric cyclizations of some chlorohydrins catalyzed by optically active cobalt (salen) type complexes

Optically active chloromethyloxirane was obtained from 1,3-dichloro-2-propanol by a process of asymmetric synthesis. The highest enantiomenc excess (e. e. ) of chloromethyloxirane that could be obtained was 67%, using Co(II) (3,5-Cl,Cl-sal)₂(S-CHXDA) and K₂CO₃ as the catalyst and base, respectively. For purpose of comparison, asymmetric cyclizations of racemic 2,3-dichloro-1-propanol and 2-chloro-1-propanol were examined; optically active chloromethyloxirane and methyloxirane were obtained according to kinetic resolution mechanisms, although the optical purities of oxiranes formed were not so high. The mechanisms for the asymmetric reactions were investigated by circular dichroism and absorption spectroscopies. It was found that the cobalt (salen) type complex forms a new complex with alkali metal carbonate, similarly to the function of crown ether. The substrate interacts with the newly formed chiral complex, followed by cylization to give optically active oxiranes.     

Asymmetric cyanosilylation of ketones catalyzed by recyclable polymer-supported copper(II) salen complexes

Various ketones have undergone asymmetric trimethylsilylcyanation at room temperature with (CH₃)₃SiCN (TMSCN) in the presence of a chiral-supported Cu(salen) complex and Ph₃PO as the catalyst. Aromatic, aliphatic, and heterocyclic ketones have been converted into the corresponding cyanohydrin trimethylsilyl ethers in 83?96% yields with 52?84% ee. Several factors concerning the reactivity and enantioselectivity have been discussed. A double activation where Cu(salen) plays the role of Lewis acid and Ph₃PO acts as a Lewis base is reported. Poly(ethylene glycol) monomethyl ether (MeO-PEG) has been used as a soluble support while JandaJel (JJ) and Merrifield (MF) resins served as insoluble supports. Each polymer is linked to the salen catalyst through a glutarate spacer. The soluble catalysts were recovered by precipitation with a suitable solvent while the insoluble catalysts were simply filtered from the reaction mixture. The JandaJel-attached Cu(salen) catalyst could be used for five cycles with the retention of efficiency and the Merrifield-bound Cu(salen) catalyst was found to loose activity with each use.     

Kinetics of cysteine autoxidation catalyzed by cobalt (II) tetrasulfophalocyanine

Kinetics of cysteine (Cys) autoxidation catalyzed by cobalt (II) tetrasulfophthalocyanine (CoTSPc) has been studied by the polarographic method. Kinetic equation derived indicates that the reaction follows a mechanism involving the formation of an intermediate ternary CoTSPc (Cys) (O₂) complex that probably contains a second Cys as RS^. radical on a macrocyclic ligand.

---

(ѕ), (II) (CoTSPc). , CoTSPc (Cys) (O₂), , RS^. .

     

Enantioselective epoxidation of unfunctionalised olefins catalyzed by Mn(salen) complexes immobilized in porous materials via phenyl sulfonic group

Heterogeneous chiral Mn(salen) catalysts axially immobilized on mesoporous materials via phenyl sulfonic groups result in remarkably higher ee values (up to 95%) for asymmetric epoxidation of unfunctionalised olefins.     

Catalytic epoxidation of cyclic vinylsilanes by ruthenium(II) complexes under aerobic conditions

A new methodology has been developed for the catalytic epoxidation of cyclic vinylsilanes using a ruthenium(II) bisoxazoline complex 2 with molecular oxygen. An attempt has been made to understand the role of -SiMe₃ group on the rate of epoxidation process.     

Probing differences in binding of methylbenzylamine enantiomers to chiral cobalt(II) salen complexes

In this work, we investigate the mode of chiral interactions between the asymmetric Co(II) salen complex, (S,S)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexane-diamine-Co(II) ([Co(1)]), and single enantiomers of methylbenzylamine (MBA) using different continuous-wave and pulsed electron paramagnetic resonance techniques combined with density functional theory computations. While [Co(1)] displays a large affinity for binding a single MBA molecule, it has a much weaker affinity for binding a second MBA molecule. Subtle differences are detected in the EPR spectra of the homochiral (S,S-[Co(1)](S-MBA)) and heterochiral (S,S-[Co(1)](R-MBA)) adducts using low [Co(1)] : MBA ratios. Moreover at high concentrations of racemic MBA, a strong preference (80%) is observed for the formation of the bis-ligated heterochiral adduct (S,S-[Co(1)](R-MBA)(2)) compared to the homochiral analogue (20% of S,S-[Co(1)](S-MBA)(2)). Differences in the (14)N hyperfine coupling from the diamine backbone in [Co(1)] were also evidenced by hyperfine sublevel correlation (HYSCORE), revealing magnetically equivalent N nuclei for the homochiral adducts and inequivalent N nuclei for the heterochiral adducts. Using DFT, these slight differences were reproduced, and explained based upon the different modes of alignment of the MBA molecule in the adduct. The current findings therefore reveal the appreciable enantiodiscrimination that occurs during the binding of MBA enantiomers to the chiral Co(II) salen complex.     

Homogeneous and heterogeneous styrene epoxidation catalyzed by copper(II) and nickel(II) Schiff base complexes

Both monomeric Schiff base complexes and 1D helical polymeric complexes of Cu(II) and Ni(II) were synthesized and characterized by physicochemical and spectroscopic methods. X-ray single-crystal studies were made on [K₂(CuL)₂Ni(CN)₄]_n·0.5nEt₂O and [K₂(NiL)₂Ni(CN)₄]_n·0.5nEt₂O. The polymers were screened as heterogeneous catalysts for styrene epoxidation. For comparison, the catalytic properties of the homogeneous and heterogeneous catalysts were also examined under identical reaction conditions, and the influence of various solvents and oxidants was studied. The polymeric catalysts showed better activities in chloroform when using tert-butyl hydroperoxide as oxidant, suggesting that heterogenization increased the activity of the catalyst under this condition.     

The effect of phenolates in the (salen)Mn-catalyzed epoxidation reactions

By addition of 2,4,6-tri-tert-butylphenolate in the Mn(salen) catalyzed epoxidation of cis-alkenes with iodosobenzene, essentially pure trans-epoxides can be obtained.     

Oxovanadium(IV), copper(II) or cobalt(II) acetylacetone complexes immobilized on amino‐functionalized CMK‐3 for the aerobic epoxidation of styrene

Oxovanadium(IV), copper(II) and cobalt(II) acetylacetone complexes have been grafted onto amino‐modified CMK‐3‐O (VO‐NH₂‐CMK‐3, Cu‐NH₂‐CMK‐3 and Co‐NH₂‐CMK‐3,respectively) and the materials thus prepared were used as heterogeneous catalysts for the aerobic oxidation of styrene. X‐ray diffraction, nitrogen adsorption–desorption and transmission electron microscopy measurements confirmed the structural integrity of the mesoporous hosts, and spectroscopic characterization techniques (Fourier transform infrared, X‐ray photoelectron, Raman) and thermogravimetry confirmed the ligands and the successful anchoring of the acetylacetone complexes to the modified mesoporous support. VO‐NH₂‐CMK‐3 displayed a relatively good catalytic performance with 94.6% of styrene conversion using air as oxidant, while Cu‐NH₂‐CMK‐3 gave 99.6% of styrene conversion using tert‐butyl hydroperoxide as oxidant. Copyright © 2015 John Wiley & Sons, Ltd.     

Chiral Mn(III) salen catalyzed oxidation of hydrocarbons

Four chiral manganese(III)-salen complexes (1–4) were employed as catalysts in the oxidation of hydrocarbons at room temperature using pentafluoroiodosylbenzene as terminal oxidant. The reactions were carried out in acetonitrile and dichloromethane. Norbornene has been selectively oxidized to exo-epoxynorborane in 85% yield. At room temperature, oxygenation of cyclohexane up to 14% in acetonitrile medium has also been achieved.     

New chiral (salen)manganese(III) systems for asymmetric epoxidation of styrene

Highly enantioselelctive and repeatable epoxidation of styrene was performed by using new chiral (salen)Mn(III) catalysts, which were derived from the initial immobilization of a homogeneous (salen)Mn(III) complex on solid carriers and subsequent dispersion into ionic liquids. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Unusual iron(II) and cobalt(II) complexes derived from monodentate arylamido ligands

The coordination chemistry of the N-substituted arylamido ligands [N(R)(C6H3R'2-2,6)] [R = SiMe3, R' = Me (L1); R = CH2But, R' = Pri (L2)] toward FeII and CoII ions was studied. The monoamido complexes [M(L1)(Cl)(tmeda)] [M = Fe (1), Co (2)] react readily with MeLi, affording the mononuclear, paramagnetic iron(II) and cobalt(II) methyl-arylamido complexes [M(L1)(Me)(tmeda)] [M = Fe (3), Co (4)]. Treatment of 2:1 [Li(L2)(THF)2]/FeCl2 affords the unusual two-coordinate iron(II) bis(arylamide) [Fe(L2)2] (5).     

Ni (II) schiff base complex immobilized on graphene oxide nano-sheets catalyzed epoxidation of alkenes

Ni (II) schiff base complex was synthesized by the reaction of nickel acetate tetrahydrate with N, N’-Bis(2,4-di-hydroxybenzaldehyde)-1,2-cyclohexanediamine and supported on modified grapheme oxide nano-sheets using 3-chloropropyltrimethoxysilane as a reactive surface modifier. The heterogeneous nano-catalyst was characterized by Fourier transform infrared spectra, X-ray diffraction, thermogravimetric analysis, transmission electron microscopy, nitrogen adsorption–desorption isotherms and atomic absorption spectroscopy. This catalyst was used for the epoxidation of alkenes using tert-butyl hydroperoxide as oxidant, giving excellent conversions and selectivity. The catalyst showed great reusability and selectivity without significant loss of activity in the epoxidation reactions.     

Cimetidine complexes derived from cobalt(II), nickel(II) and copper(II) salts of polyatomic anions

Summary Cobalt(II), nickel(II) and copper(II) complexes [M(CM)₂]X₂ (X = BF₄ or NO₃) have been prepared with cimetidine (CM). Powder data, molar conductivities, magnetic moments, i.r. and electronic spectra support apseudo-octahedral stereochemistry with MN₂N ₂ S₂ chromophore and tentative structures are proposed for the complexes. Their properties are compared with these of previously prepared complexes.