- Synthesis and characterization of a new poly α-amino acid Co(II)-complex supported on magnetite graphene oxide as an efficient heterogeneous magnetically recyclable catalyst for efficient free-coreductant gram-scale epoxidation of olefins with molecular oxygen
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A novel magnetic nanocomposite was prepared by immobilization of a cobalt complex of a synthetic poly α-amino acid on Fe3O4-doped graphene oxide (GO/Fe3O4@PAA Co(II)) and was demonstrated to be a highly efficient catalyst for the epoxidation of olefins in mild conditions. PAA was synthesized through a multi-step synthesis, first by a poly condensation reaction of salicylaldehyde followed by the Strecker synthesis. The synthesized nanocomposite was characterized by various analytical and spectroscopic methods including FTIR, ICP, XRD, EDX, XPS, FE-SEM, TEM, TGA, VSM and DLS analyses. A wide variety of olefins could be tolerated toward epoxidation in the presence of molecular oxygen without the need for any co-reductant. The magnetic nanocomposite could be readily separated by a magnet from the mixture and reused for several times without any significant reactivity loss, which represents its potential for practical and industrial application. Also, the scalability of the process was investigated in this work.
- Kazemnejadi, Milad,Mahmoudi, Boshra,Sharafi, Zeinab,Nasseri, Mohammad Ali,Allahresani, Ali,Esmaeilpour, Mohsen
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- Co(II) Schiff base complex decorated on polysalicylaldehyde as an efficient, selective, heterogeneous and reusable catalyst for epoxidation of olefins in mild and self-coreductant conditions
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Abstract: A new Co(II)-Schiff base complex was decorated on a polysalicylaldehyde (PSA) framework and used as a selective and efficient catalyst for the epoxidation of alkenes in the presence of O2 as a green source of oxygen without aco-reductant. The catalyst was characterized step by step by FTIR, UV–Vis, 1H NMR, TGA, CHN, XPS and EDX analyses. Loading an amount of Co ions in the catalyst as well as its leaching amount were studied by an ICP-OES instrument. The catalyst demonstrated excellent activity for the of a variety of alkenes in a mild, inexpensive and efficient protocol. Also, the catalyst can be simply recovered from the reaction mixture and reused for several times without any noteiceable loss in its activity. Reaction parameters including temperature, oxygen flow volume, catalyst amount and solvent were screened by reaction time. Catalytic studies including XPS spectroscopy and some blank experiments were performed to obtain an initial insight into the reaction mechanism. Also, the reactivity of the novel catalyst was evaluated as the turnover frequency. Graphical Abstract: A new and efficient protocol have been developed for the selective epoxidation of olefins using a heterogeneous recyclable Co(II)-Schiff base complex of polysalicylaldehyde in mild and self-coreductant conditions by molecular oxygen.
- Kazemnejadi, Milad,Shakeri, Alireza,Nikookar, Mahsa,Mohammadi, Mohammad,Esmaeilpour, Mohsen
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p. 6889 - 6910
(2017/10/05)
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- An efficient epoxidation of terminal aliphatic alkenes over heterogeneous catalysts: When solvent matters
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The epoxidation of unfunctionalized terminal aliphatic alkenes over heterogeneous catalysts is still a challenging task. Due to the tuning of a peculiar catalyst/oxidant/solvent combination, it was possible to attain good alkene conversions (73%) and excellent selectivity values (>98%) in the desired terminal 1,2-epoxide. Over the titanium-silica catalyst and in the presence of tert-butylhydroperoxide, the use of α,α,α-trifluorotoluene as an uncommon non-toxic solvent was the key factor for a marked enhancement of selectivity. The titanium-silica catalyst was efficiently recycled and reused after a gentle rinsing with fresh solvent.
- Palumbo,Tiozzo,Ravasio,Psaro,Carniato,Bisio,Guidotti
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p. 3832 - 3839
(2016/06/13)
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- C2-bridged metallocene dichloride complexes of the types (C13H8-CH2CHR-C9H 6-nR′n)ZrCl2 and (C13H8-CH2CHR-C13H 8)MCl2 (n=0, 1; R=H, alkenyl; R′=alkenyl, benzyl; M=Zr, Hf) as self-immobilizing catalyst precursors for ethylene polymerization
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A total of 15 C2-bridged fluorenylidene indenylidene and bis(fluorenylidene) metal dichloride complexes (metal=Zr, Hf) and the corresponding ligand precursors have been prepared and characterized. ω-Alkenyl substituents with various chain lengths in the C2-bridge or in position 3 of the indenylidene moiety have an impact on the polymerization activity of the catalysts and the molecular weights of the produced polyethylenes. These ω-alkenyl substituents cause 'self-immobilization' due to their incorporation into the backbone of a growing polymer chain providing heterogeneous catalyst systems.
- Alt, Helmut G.,Jung, Michael
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- Electroorganic synthesis 65. Anodic homocoupling of carboxylic acids derived from fatty acids
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Fatty acid derived carboxylic acids with double bonds, hydroxy-, amino-, keto-, ester- and epoxy groups are anodically coupled to dimers (Kolbe electrolysis) in 29 to 81% yield and up to a 2.5 mol scale. Problems due to the low conductivity of fatty acid salts were overcome by the use of a flow cell with a narrow electrode gap. Fatty acids with branched alkyl chains gave dimers with interesting emulsifying properties. Dimethyl hexadecanedioate, accessible from methyl azelate, could be cyclized and further converted into homomuscone and muscone in a few steps. A commercial mixture of dimeric fatty acids (C36-dicarboxylic acids) has been coupled to give C70-diesters. Acta Chemica Scandinavica 1998. Part 64: Nielsen, M. F., Batanero, B.,.
- Weiper-Idelmann, Andreas,Aus Dem Kahmen, Martin,Schaefer, Hans J.,Gockeln, Marianne
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p. 672 - 682
(2007/10/03)
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- Synthesis of diols, for use as intermediates for polymeric materials, by starting from terminal diolefins
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Disclosed is the synthesis of terminal diols, which are organic intermediates used in order to produce polymeric materials, by starting from terminal diolefins, which synthesis is based on the oxidation of diolefins to yield diepoxides, in a double-phase aqueous-organic system with hydrogen peroxide and in the presence of catalysts soluble in the organic phase, followed by a reaction of reduction of the resulting diepoxides.
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