Bismuth-Substituted “Sandwich” Type Polyoxometalate Catalyst for Activation of Peroxide: Umpolung of the Peroxo Intermediate and Change of Chemoselectivity
作者:Srinivasa Rao Amanchi、Alexander M. Khenkin、Yael Diskin-Posner、Ronny Neumann
DOI:10.1021/acscatal.5b00066
日期:2015.6.5
formation of a nucleophilic peroxo intermediate. There are two lines of evidence that support the formation of a reactive nucleophilic peroxo intermediate: (1) More electrophilic sulfoxides are more reactive than more nucleophilic sulfides, and (2) nonfunctionalized aliphatic alkenes and dienes showed ene type reactivity rather than epoxidation pointing toward “dark” formation of singletoxygen from the
W VI,Mo VI,V V和Ti IV化合物用过氧化物对烯烃进行环氧化是公认的方法,并且公认的是,活性中间过氧化物对亲核底物是亲电子的。Polyoxotungstates,例如,那些在“三明治”结构,[WZn(TM-L)的2(ZnW 9 ö 34)2 ] q - ,其中TM =过渡金属和L = H 2 O,在过去已经发现是出色的环氧化催化剂。现已发现,用刘易斯基本的Bi III代替进入“三明治”多金属氧酸盐结构的末端位置,生成[Zn 2 Bi III 2(ZnW 9 O 34)2 ] 14–导致明显的过氧化物种类的形成和亲核过氧化物中间体的形成。有两条证据支持反应性亲核过氧中间体的形成:(1)更多的亲电子亚砜比更多的亲核硫化物更具反应性;(2)未官能化的脂肪族烯烃和二烯显示出烯型反应性,而不是环氧化,指向“亲核中间体过氧物种形成单线态氧的“暗”形。烯丙醇的反应比烯烃快得多,但对醇的C–H
Co-Condensation Assisted Preparation of MoVI Schiff Base Modified Mesoporous Silica Catalyst for Enhanced Epoxidation of Olefins
reaction. The heterogeneouscatalyst showed good catalytic activities in the liquid-phase epoxidation of olefins with t-BuOOH as the oxygen source in 1,2-dichloroethane solvent at 80°C. Several important factors, including oxidant-to-substrate ratio, solvent, and catalyst reusability, were investigated. Under the optimum reaction conditions, using this heterogeneouscatalyst for the cyclohexene epoxidation
一种有机-无机催化剂是通过对水杨基氨基苯甲酸与经3-氯丙基修饰的中孔二氧化硅反应制得的。在制备过程中,原硅酸四乙酯(TEOS)和3-氯丙基三甲氧基硅烷(CPTES)发生水解和共缩合。然后将MoO 2(acac)2引入经席夫碱配体官能化的介孔二氧化硅中。通过元素分析,X射线衍射(XRD),傅立叶变换红外光谱(FT-IR),扫描电子显微镜(SEM),透射电子显微镜(TEM)等一系列技术研究了制备的催化剂的结构性能。 ),N 2吸附/解吸曲线和热重分析(TGA)。结果表明,Mo VI Schiff碱配合物已成功地束缚在二氧化硅载体上,并且在锚固反应后,SBA-15型二氧化硅的六角有序介孔结构得以很好地保留。非均相催化剂显示出与烯烃的液相环氧化良好的催化活性吨-BuOOH作为氧源,在80°C下的1,2-二氯乙烷溶剂中。研究了几个重要因素,包括氧化剂与底物的比例,溶剂和催化剂的可重复使用性。在最佳反
Ultrasound-Assisted Epoxidation of Olefins and α,β-Unsaturated Ketones over Hydrotalcites Using Hydrogen Peroxide
作者:Unnikrishnan R. Pillai、Endalkachew Sahle-Demessie、Rajender S. Varma
DOI:10.1081/scc-120021028
日期:2003.7
Abstract An efficient ultrasound-assisted epoxidation of olefins and α,β-unsaturated ketones over hydrotalcite catalysts in the presence of hydrogenperoxide and acetonitrile is described. This general and selective protocol is relatively fast and is applicable to a wide variety of substrates.
in the zeolite framework while a minority exists in the form of isolated octahedrally coordinated Ti(VI) at framework or extra-framework positions. The obtained Ti-Beta zeolites are highly active and selective catalysts for the epoxidation of unsaturated ketones, e.g. 2-cyclohexen-1-one, with hydrogen peroxide as an oxidant. A quasilinear correlation between the epoxidation rate and the number of framework
Three powerful dinuclear metal–organic catalysts for converting CO<sub>2</sub> into organic carbonates
作者:Dan Zhao、Xiao-Hui Liu、Zhuang-Zhi Shi、Chen-Dan Zhu、Yue Zhao、Peng Wang、Wei-Yin Sun
DOI:10.1039/c6dt02755e
日期:——
NH2-functionalized tripodal ligand 2-((bis(2-aminoethyl)amino)methyl)phenol (HL), three dinuclear metal–organic complexes [Zn(L)]2·2ClO4 (1), [Cu(L)]2·2ClO4·2H2O (2) and [Cd(L)]2·2ClO4 (3) have been successfully isolated and structurally characterized using single-crystal X-ray diffraction analyses. Considering the dinuclear metal centers and the NH2-functional groups in the structures, 1–3 were investigated as