83816-59-5Relevant academic research and scientific papers
Synthesis of new chiral Mn(iii)-salen complexes as recoverable and reusable homogeneous catalysts for the asymmetric epoxidation of styrenes and chromenes
Chaudhary, Pooja,Damodaran, Krishna K.,Singh, Surendra,Yadav, Geeta Devi
, p. 1308 - 1318 (2022/02/07)
New chiral Mn(iii)-salen complexes 1a-e and 2a-e were synthesized from the reaction of C2-symmetric chiral salen ligands and Mn(CH3COO)2·4H2O under an inert atmosphere followed by aerobic oxidation. These complexes were obtained in 91-96% yields and characterized by HRMS, FT-IR, UV-visible spectroscopy, TGA, and elemental analysis. The chiral Mn(iii)-salen complexes 1a-e and 2a-e were evaluated in the asymmetric epoxidation of styrene using NaOCl as an oxidant in ethyl acetate as a green solvent. The chiral Mn(iii)-salen complexes 1b and 2b (2 mol%) catalyzed the asymmetric epoxidation of substituted styrenes and chromenes to afford the corresponding epoxides in 95-98% yields with 29-88% ee's. The catalysts 1b and 2b were recovered and reused for up to 2 and 3 runs, respectively, in the asymmetric epoxidation of styrene, and the yield of styrene oxide gradually decreased but the ee was consistent.
A Novel Synthesis of 2-Ferrocenoyl-Substituted Iodobenzofurans
Li, Yang,Zhuoma, Bairenqing,Gao, Wentao
, p. 764 - 768 (2017/02/03)
In the present investigation, the first construction of a series of structurally new 2-ferrocenoyl-substituted iodobenzofurans hybrids has been achieved through a simple and mild two-step procedure, involving the iodination of salicylaldehydes using N-iodosuccinimide reagent in eco-friendly PEG-400 medium at room temperature followed by one-pot Rap–Stoermer reaction with 1-chloroacetylferrocene in refluxing MeCN with the presence of K2CO3as base and PEG-400 as the activated additive. These newly synthesized compounds belong to a new class of ferrocene-benzofuran hybrids and could be good candidates for the development of compounds for use in medicinal chemistry.
Di- and trinuclear iron/titanium and iron/zirconium complexes with heterocyclic ligands as catalysts for ethylene polymerization
G?rl, Christian,Betthausen, Eva,Alt, Helmut G.
, p. 37 - 51 (2016/08/23)
The properties of polyolefin resins depend very much on their molecular weights, the amount of side chain branchings and molecular weight distributions. One way to obtain such tailored products in only one reaction step consists in the application of dissymmetric multi nuclear catalysts with different active sites. Since every active site is producing its own polymer, a “molecular blending” is the result. In order to reach this goal, a variety of mono, di- and trinuclear complexes of iron, titanium and zirconium, containing 2,6-bis(aryliminoethyl)pyridine and phenoxyimine building blocks have been synthesized and characterized. The reaction of iodo functionalized 2,6-bis(arylimino-ethyl)pyridine derivatives with alkyne functionalized phenoxyimine compounds via Sonogashira cross-coupling reactions results in ligand precursors that can provide coordination sites for two different metals. Trinuclear complexes with the combinations Ti/Fe and Zr/Fe, each molecule containing two iron atoms in two 2,6-bis(aryliminoethyl)pyridine units, gave the best ethylene polymerization results. Due to fast ligand exchange reactions, dinuclear iron/titanium complexes could not be isolated from reactions of mono(phenoxyimine) titanium complexes and the coupled bis(chelate) ligand precursor. Since the metal centers show their best performances at different polymerization temperatures, the compositions (and, therefore, the molecular weight distributions) of the desired polyethylenes may be adjusted by a simple change of the reaction temperature.
Di- and trinuclear zirconium complexes as catalysts for ethylene polymerization
Rimkus, Andrea M.,Alt, Helmut G.
, p. 30 - 40 (2016/08/09)
Bimodal and multimodal molecular weight distributions of polyethylenes can be achieved with di- or trinuclear zirconium catalysts in homogeneous solution. In order to prepare such complexes, bis(phenoxyimine) zirconium complexes and zirconocene complexes were coupled in Sonogashira reactions. Hydrosilylation reactions were applied for the combination of metallocene complexes with silane substituted N-heterocyclic compounds, such as 3,5-dimethylpyrazoles. The resulting di- and trinuclear complexes were activated with methylaluminoxane (MAO) and applied as catalysts for ethylene polymerization. The catalytic performances of these complexes and their applications in olefin polymerization reactions are discussed.
(R,R)-salen/salan-based polymer fluorescence sensors for Zn2+ detection
Song, Fengyan,Ma, Xiao,Hou, Jiali,Huang, Xiaobo,Cheng, Yixiang,Zhu, Chengjian
experimental part, p. 6029 - 6036 (2012/04/10)
(R,R)-salen-based polymer fluorescence sensor P-1 could be synthesized by the polymerization of 5,5′-(isoquinoline-5,8-diylbis(ethyne-2,1-diyl))- bis(3-tert-butyl-2-hydroxybenzaldehyde) (M-1) with (R,R)-1,2-diaminocyclohexane (M-2) via nucleophilic addition-elimination reaction, and (R,R)-salan-based polymer sensor P-2 could be obtained by the reduction reaction of P-1 with NaBH4. The fluorescence response behaviors of two chiral polymers P-1 and P-2 on Zn2+ were investigated by fluorescence spectra. The fluorescence intensities of P-1 and P-2 can exhibit gradual enhancement upon addition of Zn2+. Compared with other cations, such as Na +, K+, Mg2+, Ca2+, Fe3+, Co2+, Ni2+, Cu2+, Ag+, Cd 2+, Cr3+ and Pb2+, Zn2+ can lead to the pronounced fluorescence enhancement as high as 22.8-fold for P-1 and 3.75-fold for P-2, respectively. The results show that P-1 and P-2 incorporating (R,R)-salen/salan moieties as receptors in the polymer main chain backbone can exhibit high sensitivity and selectivity for Zn2+ detection.
One-electron oxidation of electronically diverse manganese(III) and nickel(II) salen complexes: Transition from localized to delocalized mixed-valence ligand radicals
Kurahashi, Takuya,Fujii, Hiroshi
supporting information; experimental part, p. 8307 - 8316 (2011/07/08)
Ligand radicals from salen complexes are unique mixed-valence compounds in which a phenoxyl radical is electronically linked to a remote phenolate via a neighboring redox-active metal ion, providing an opportunity to study electron transfer from a phenola
Chiral linear polymers bonded alternatively with salen and 1,4-dialkoxybenzene: Synthesis and application for Ti-catalyzed asymmetric TMSCN addition to aldehydes
Sakthivel, Sekarpandi,Punniyamurthy, Tharmalingam
experimental part, p. 2834 - 2840 (2011/03/19)
The synthesis of chiral linear polymers 1a-b having salen and 1,4-dioctyloxybenzene as alternate segments has been accomplished. The GPC analysis showed the molecular weights corresponding to ca. 15 (Mw = 10,999, Mn = 9165 and PDI = 1.20) repeating units for 1a and ca. 8 (Mw = 8547, Mn = 7883 and PDI = 1.08) repeating units for 1b. Polymers 1a-b have been studied with Ti(OiPr)4 as a recyclable catalyst for the asymmetric addition of TMSCN to aldehydes while the selectivity of the polymer catalyst is identical to that of the monomer. The reactions are efficient affording the cyanohydrins with up to 88% ee. The selectivity of the polymer based catalyst 9a is found to be the same to that of the monomer 10a. The reaction provides the advantages of simplified product isolation and easy recovery and recyclability of polymer catalyst 9a without any loss of activity or selectivity.
Self-assembled dinuclear cobalt(II)-salen catalyst through hydrogen-bonding and its application to enantioselective nitro-aldol (Henry) reaction
Park, Jongwoo,Lang, Kai,Abboud, Khalil A.,Hong, Sukwon
supporting information; experimental part, p. 16484 - 16485 (2009/04/13)
Novel chiral dinuclear Co(II)-salen catalysts self-assembled through the pyridone/aminopyridine hydrogen-bonding pair have been developed. The self-assembled dinuclear Co(II)-Salen catalyst results in significant rate acceleration (48 times faster rate) a
The combination of mononuclear metallocene and phenoxyimine complexes to give trinuclear catalysts for the polymerization of ethylene
G?rl, Christian,Alt, Helmut G.
, p. 5727 - 5753 (2008/03/13)
Trinuclear complexes were synthesized by combination of metallocene and phenoxyimine zirconium complexes. After activation with methylalumoxane (MAO), these catalysts polymerize ethylene with moderate and good activities. Due to the presence of different catalytic centers, polyethylenes with broad or bimodal molecular weight distributions were obtained.
Synthesis and catalytic properties of p-acylthio(phenylacetylene)n substituted chiral manganese salen complexes
Nielsen,Gothelf
, p. 2440 - 2444 (2007/10/03)
The syntheses of three new salen ligands that are tethered to a p-acylthio(phenylacetylene)n linker are described. The two key steps in the syntheses are coupling of the p-acylthio(phenylacetylene)n linker (n = 0-2) with a 5-iodosali
