Highly efficient epoxidation of electron-deficient olefins with tetrabutylammonium peroxydisulfate

The epoxidation of α,β-unsaturated carbonyl compounds such as enones and enals was efficiently achieved with tetrabutylammonium peroxydisulfate in the presence of equimolar amounts of hydrogen peroxide and NaOH in acetonitrile or methanol at 25 °C in excellent yields. Base-sensitive substrate such as cinnamaldehyde could be successfully epoxidized in short reaction time under mild reaction conditions.     

Anthracene-induced turnover enhancement in the manganese porphyrin-catalyzed epoxidation of olefins

Anthracene and related compounds function as lifetime-extending cofactors in the (meso-tetraphenylporphine)Mn(III) chloride-catalyzed epoxidation of olefins. An experiment with a chiral porphyrin catalyst shows that enantioselectivity is preserved in the presence of the cofactor. Additional experiments show that (a) turnover number enhancement is greatest for the least reactive substrates, (b) derivatization of anthracene at the 9 and 10 positions largely eliminates the enhancement effect, and (c) anthracene is ultimately converted to anthraquinone. The origin of the observed enhancements is in the reaction of anthracene with the normally unreactive dimeric oxo-bridged form of the catalyst. This reaction, which produces anthraquinone, regenerates the catalytically active monomeric form of the manganese porphyrin.     

Enantioselective electrocatalytic epoxidation of olefins by chiral manganese Schiff-base complexes

Asymmetric electrocatalytic epoxidation of olefins has been achieved with chiral manganese Schiff-base complexes immobilized on a glassy carbon electrode surface using molecular dioxygen as oxidant. The electrocatalytic system gives moderate enantiomeric excess (ee) values (65–77%) for the epoxidation of cis-stilbene, trans-stilbene and styrene. Our results indicated that the catalyst turnover number is significantly improved when the manganese complexes are immobilized on the electrode surface, which can be attributed to the suppression of the formation of inactive manganese dimer when the active metal centres are attached to the polymer network.     

Efficient epoxidation reaction of terminal olefins with hydrogen peroxide catalyzed by an iron (II) complex

A highly active iron (II) complex that catalyzed epoxidation of terminal olefins with hydrogen peroxide was described. The catalytic system displayed excellent catalytic ability for the selective oxidation of terminal olefins to epoxides with high selectivity (up to 97.8%) in CH₃CN at 25?°C. The catalytic activity of three similarly structural iron (II) complexes was comparatively studied. The effect of various auxiliary ligands on epoxidation was investigated in detail.     

Novel N-alkylation of a schiff base with electron-deficient olefins

The reaction of 2,3,4,5-tetrahydropyridine with electron-deficient olefins such as methyl acrylate, acrylonitrile, and N-phenylmaleimide, provided 1-(2-methoxycarbonylethyl)-5-[1- (2-methoxycarbonylethyl)-2-piperidyl]-1,2,3,4-tetrahydropyridine, 1-(2-cyanoethyl)-5-[1-(2-cyanoethyl)-2-piperidyl]-1,2,3,4-tetrahydropyridine, and 2-(2-methoxypiperidino)-N-phenylsuccinimide, respectively, in high yields.     

Cross-metathesis of 1,3-dienes with electron-deficient olefins

Cross-metathesis reactions between 1,3-dienes and electron-deficient olefins have been investigated. Terminal monosubstituted 1,3-dienes afforded low yields of the desired CM products due to competing cleavage of the internal double bond. This undesired cleavage is successfully suppressed in the case of 1,3-dienes containing a sterically more congested internal double bond. Methyl vinyl ketone as the coupling partner was shown to provide the best yields.     

Electrochemical iodofluorination of electron-deficient olefins

Electron-deficient olefins like α,β-unsaturated ester, amide, and phosphonate reacted with iodonium cation species generated by the anodic oxidation of iodide anion in Et₃N-5HF/CH₃NO₂ to form corresponding iodofluorinated compounds in good to moderate yields. The reaction proceeds at room temperature under air atmosphere and constant current conditions. The iodofluorinated products were shown to be useful fluorine-containing building blocks.     

Electrochemical fluoro-selenenylation of electron-deficient olefins

Electrochemical fluoro-selenenylation of electron-deficient olefins like α,β-unsaturated ester, carboxylic acid, amide, and phosphonate was successfully carried out by the anodic oxidation of diphenyl diselenide in the presence of olefins in Et₃N·5HF/CH₃NO₂. The anodically generated benzeneselenenyl fluoride [PhSeF] equivalent was stable in the electrolytic solution, which resulted in the efficient fluoro-selenenylation. The fluoro-selenenylation products were shown to be potential useful fluoro-building blocks.     

Palladium-catalyzed cyclopropanation of electron-deficient olefins with aryldiazocarbonyl compounds

A concise and efficient protocol for the preparation of cyclopropanes from various aryldiazocarbonyl compounds and electron-deficient olefins catalyzed by Pd(OAc)₂ is reported.     

Copper hydride-catalyzed reduction of electron-deficient olefins

Copper hydride derived from CuF(PPh₃)₃·2MeOH-bis[(2-diphenylphosphino)phenyl] ethersilane can reduce electron-deficient olefins selectively and efficiently.     

Efficient and selective peracetic Acid epoxidation catalyzed by a robust manganese catalyst

A manganese catalyst containing a tetradentate ligand derived from triazacyclononane exhibits high catalytic activity in epoxidation reactions using peracetic acid as oxidant. The system exhibits broad substrate scope and requires small (0.1-0.15 mol %) catalyst loading. The catalyst is remarkably selective toward aliphatic cis-olefins. Mechanistic studies point toward an electrophilic oxidant delivering the oxygen atom in a concerted step.     

Asymmetric epoxidation of conjugated olefins with dioxygen

A complex situation: Asymmetric epoxidation of conjugated olefins was achieved at room temperature using ruthenium complex 1 as the catalyst and air as the oxidant to give epoxides in up to 95?%?ee. When the product was acid sensitive, the reaction was carried out at 0?°C under oxygen.     

Enantioselective 1,3-dipolar cycloadditions of diazoacetates with electron-deficient olefins

[reaction: see text] A general strategy for highly enantioselective 1,3-dipolar cycloaddition of diazoesters to beta-substituted, alpha-substituted, and alpha,beta-disubstituted alpha,beta-unsaturated pyrazolidinone imides is described. Cycloadditions utilizing less reactive alpha,beta-disubstituted dipolarophiles require elevated reaction temperatures, but still provide the corresponding pyrazolines with excellent enantioselectivities. Finally, an efficient synthesis of (-)-manzacidin A employing this cycloaddition methodology as a key step is illustrated.     

脯氨酸衍生的胺基吡啶四氮锰配合物催化双氧水参与的烯烃不对称环氧化反应（英文）

自然界中存在许多的金属酶,它们参与促进各种各样的氧化反应,例如羟化反应,环氧化反应等.金属酶催化的反应具有催化效率高、反应条件温和、选择性高等优点.受大自然中的金属酶结构及其性质的启发,人们提出了仿生催化氧化的理念,并开始对金属酶进行模拟,致力于发展清洁氧化的反应方式.在过去的几十年中,科学家们设计合成了一系列仿生金属配合物催化剂.例如,利用非手性的乙二胺骨架设计合成出四齿氮配体MEP(N,N'-dimethylN,N'-bis(2-pyridinylmethyl)ethane-1,2-diamine),将其制备成相应的铁配合物催化剂,该铁催化剂可以很好的实现脂肪族烯烃的环氧化,产率高达90%.2003年,Stack小组首次报道了利用手性N,N-二甲基环己二胺骨架衍生的四齿氮配体金属配合物Mn-MCP-(OTf)2(MCP=N,N-dimethyl-N,N-bis(2-pyridylmethyl)cyclohexane-trans-1,2-diamine)催化的不对称环氧化反应.该反应的对映选择性仅仅为10%.因此,发展新型手性四氮配体金属配合物,用于高产率、高对映选择性的不对称环氧化反应,值得进行深入研究.近年来发展的一些含手性二胺骨架的四齿氮配体,例如PDP(2-[[2-(1-(pyridin-2-ylmethyl)-pyrrolidin-2-yl)pyrrolidin-1-yl]methyl]pyridine),被应用到不对称环氧化反应中,但是其手性二胺骨架为联吡咯,价格昂贵,难以制备.这在很大程度上限制了其在不对称合成中的实际应用.因此,利用一些易于合成的手性二胺骨架,发展结构新颖、催化性能优良的四氮金属配合物,成为实现高效、高选择性不对称环氧化反应的关键.在之前的工作基础上,本文以简单易得、价格低廉的天然氨基酸——L-脯氨酸为起始原料,选取吡啶环和含取代基的吡啶环作为侧基氮供体,制备了三种手性四齿氮配体.随后,我们利用新发展的手性四齿氮配体,合成了相应的锰配合物,并且分别将其运用于烯烃不对称环氧化反应中,仔细评估了这些锰金属配合物的催化性能.建立了以0.2 mol%的锰配合物为催化剂,0.5当量的2,2-二甲基丁酸为添加剂,30%双氧水为氧化剂,反应温度为–30 oC,乙腈为溶剂的催化不对称环氧化反应体系.反应结果显示:该催化剂催化的不对称环氧化反应底物适用性广泛,其中苯乙烯、苯并吡喃、烯酰胺等化合物均可以被成功地转化为相应的环氧化物,得到中等至优异的对映选择性(产率最高可达95%,对映选择性最高可达99%).     

Samarium triiodide-catalyzed conjugate addition of indoles with electron-deficient olefins

The SmI₃-catalyzed reaction of indoles with electron-deficient olefins generated the corresponding Michael adducts in high yields. The substitution on the indole nucleus occurred exclusively at the 3-position and N-alkylation products have not been observed.     

Theoretical and experimental investigations of the enantioselective epoxidation of olefins catalyzed by manganese complexes

The enantioselective epoxidation of olefin by Mn^II（R,R-PMCP）(OTf)2, H₂O₂ and H₂SO₄ was explored by DFT calculations and experiments. Theoretical results suggest that [MnV（O）(R,R-PMCP)（SO4）]+species with a triplet ground spin state serves as the active species for the olefin epoxidation. It can be generated by the H₂SO₄ assisted O-O heterolysis of Mn^III（OOH） species. Mn^III-persulfate is also involve...     

Theoretical and experimental investigations of the enantioselective epoxidation of olefins catalyzed by manganese complexes

The enantioselective epoxidation of olefin by Mn^II（R,R-PMCP）(OTf)2, H₂O₂ and H₂SO₄ was explored by DFT calculations and experiments. Theoretical results suggest that [MnV（O）(R,R-PMCP)（SO4）]+species with a triplet ground spin state serves as the active species for the olefin epoxidation. It can be generated by the H₂SO₄ assisted O-O heterolysis of Mn^III（OOH） species. Mn^III-persulfate is also involve...     

Synthesis and some properties of a cationic manganese cyclopentadienylallyldicarbonyl complex

Conclusions A single-step synthesis was carried out for a cationic manganese cyclopentadienylallyldicarbonyl complex and the reactions of this complex with nucleophilic reagents were studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 644–648, March, 1983.The authors express their gratitude to P. V. Petrovskii for taking the¹³C NMR spectrum and to A. S. Peregudov for taking the PMR spectra.     

非血红素铁、锰配合物催化烯烃不对称环氧化反应研究进展

手性环氧化物是重要的有机反应中间体.金属氧化酶催化的氧化反应通常具有高效、高选择性、反应条件温和和绿色的特点,模拟其中的非血红素铁加氧酶设计合成一系列手性四氮铁锰配合物催化烯烃不对称环氧化反应成为获得高产率、高对映选择性的手性环氧化物的一个重要方法.本文综述了近年来非血红素手性四氮铁锰配合物催化烯烃不对称环氧化反应的研究进展及相应的机理研究.