- Development of a halide-free aluminium-based catalyst for the synthesis of cyclic carbonates from epoxides and carbon dioxide
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Kinetic studies of the synthesis of glycerol carbonate from glycidol and carbon dioxide have been carried out. These showed that under suitable reaction conditions, bimetallic aluminium(salen) complex 4 is able to catalyse the conversion of epoxides into the corresponding cyclic carbonates without the need for a co-catalyst.
- Castro-Osma, Jose A.,North, Michael,Wu, Xiao
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- Oxidorhenium(V) Complexes with Tetradentate Iminophenolate Ligands: Influence of Ligand Flexibility on the Coordination Motif and Oxygen-Atom-Transfer Activity
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The synthesis of oxidorhenium(V) complexes 1-3 coordinated by tetradentate iminophenolate ligands H2L1-H2L3 bearing backbones of different rigidity (alkyl, cycloalkyl, and phenyl bridges) allows for the formation of distinct geometri
- Zwettler, Niklas,Schachner, J?rg A.,Belaj, Ferdinand,M?sch-Zanetti, Nadia C.
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- Encapsulation of chiral Fe(salen) in mesoporous silica structures for use as catalysts to produce optically active sulfoxides
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Solid catalysts which are heterogeneous at the macroscopic scale but homogeneous at the microscopic level were prepared by the encapsulation of Fe(salen) by a "ship in a bottle" approach. This approach permits the synthesis of a "free" Fe(salen) complex inside the nanocages of SBA-16 and m-MCF, having conformational freedom and behaving as a complex in solution. These materials were used as catalysts for asymmetric oxidation of sulfides. The entrance sizes of the mesoporous materials SBA-16 and m-MCF were tuned by changing the synthesis parameters and by silylation of the silica surface with n-propyl groups, which resulted in materials with different Fe(salen) loadings. Chiral Fe(salen) trapped in m-MCF materials showed higher activity than the complex immobilized on SBA-16. The activity and enantioselectivity of the catalysts based on m-MCF were on a par with the homogeneous counterpart under specific conditions. The heterogenized catalysts presented a limited recyclability; however, they were clearly advantageous compared to the homogenous counterpart, where reutilization was not possible.
- Oliveira, Rafael L.,Nijholt, Tom,Shakeri, Mozaffar,De Jongh, Petra E.,Gebbink, Robertus J. M. Klein,De Jong, Krijn P.
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- Reducing the cost of production of bimetallic aluminium catalysts for the synthesis of cyclic carbonates
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Bimetallic aluminium complexes of general formula [(salen)Al]2O or [(acen)Al]2O catalyse the formation of cyclic carbonates from carbon dioxide and terminal epoxides under exceptionally mild reaction conditions. To improve the potential for industrial scale application of these catalysts, the cost of their production has been evaluated and reduced significantly by optimization of the synthesis, including replacement of the most expensive chemicals by less expensive alternatives. The largest cost saving was associated with the formation of aluminium triethoxide insitu, which reduced the cost of the chemicals need for production of the catalysts by 49-87%. Further savings were made by avoiding the use of tetrabutylammonium bromide and acetonitrile, resulting in overall cost savings of 68-93%. Copyright
- North, Michael,Young, Carl
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- Stereoselective protonation of 2-methyl-1-tetralone lithium enolate catalyzed by salan-type diamines
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Asymmetric protonation of ketone enolates is a convenient alternative to asymmetric alkylation of enolates that allows to convert racemic ketones into their optically active form. Here, we have reported an efficient enantioselective protonation of 2-methyl-1-tetralone lithium enolate catalyzed by salan-type diamines. A broad series of salan-type catalysts were synthesized, including several previously unknown, and subsequently tested in the title reaction. For the first time, a chiral amine used as organocatalyst has shown better results than as stoichiometric protonating agent. Application of only 10 mol% of salan allows to obtain the title ketone with high yield and enantiomeric excess up to 75%. The DFT calculations of the structure of the catalyst and its complex with lithium enolate were conducted, which makes it possible to propose a likely reaction mechanism.
- ?owicki, Daniel,Watral, Justyna,Jelecki, Maciej,Bohusz, Wiktor,Kwit, Marcin
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- Switchable Polymerization Triggered by Fast and Quantitative Insertion of Carbon Monoxide into Cobalt–Oxygen Bonds
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A strategy that uses carbon monoxide (CO) as a molecular trigger to switch the polymerization mechanism of a cobalt Salen complex [salen=(R,R)-N,N′-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine] from ring-opening copolymerization (ROCOP) of ep
- Poli, Rinaldo,Wang, Yong,Xie, Xiaolin,Xu, Jing,Zhao, Yajun,Zhou, Xingping,Zhu, Shuaishuai
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supporting information
p. 5988 - 5994
(2020/02/25)
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- Polymerization of Ethylene in the Presence of Titanium(IV), Zirconium(IV), and Vanadium(V) Coordination Compounds with Salen Ligands
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Abstract: Coordination compounds of titanium(IV), zirconium(IV), and vanadium(V) with chiral salen ligands have been obtained and characterized, and their catalytic activity in the polymerization reaction of ethylene has been studied. It has been shown that in the presence of polymethylaluminoxane as a cocatalyst, the activity of the titanium-containing catalyst system reaches 944 kgPE mol(Ti)?1 h?1 and leads to the preparation of ultrahigh-molecular-weight polyethylene.
- Bulychev, B. M.,Gagieva, S. Ch.,Lyadov, A. S.,Takazova, R. U.,Tuskaev, V. A.
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p. 291 - 297
(2020/05/25)
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- Schiff base manganese compound, preparation method thereof and application thereof
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The present invention provides a Schiff base manganese compound, a preparation method thereof and an application thereof. The Schiff base manganese compound has a structure of a formula I. The provided Schiff base manganese compound has a NNOO tridentate coordination ability to form a metal active center binding site to obtain a tetracoordinate Schiff base manganese catalyst. The Schiff base manganese compound is used to catalyze a ring-opening polymerization of lactide and caprolactone; the Schiff base manganese catalyst has very high activity for the ring-opening polymerization of the lactide and caprolactone, can also realize the polymerization of the monomers at room temperature, at the same time has a certain selectivity to the racemic lactide and can slightly improve the regularity of the microscopic chain structure of the polymerization product. Under the action of the catalyst, a monomer conversion rate of polylactic acid can reach 89-96%; the stereoregularity Pm of the obtained polylactic acid can reach 0.43-0.60; and a monomer conversion rate of polycaprolactone can reach 90%-95%.
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Paragraph 0080; 0081
(2019/01/07)
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- Salen(Co(III)) imprisoned within pores of a metal-organic framework by post-synthetic modification and its asymmetric catalysis for CO2 fixation at room temperature
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Herein, a new preparation strategy of chiral metal-organic frameworks (CMOFs) has been demonstrated. By adsorption and then post-synthetically modified (PSM) procedures, chiral salen(Co(iii)) could be imprisoned within the cages of an MOF and remained in its free form. This is the first report on the successful application of CMOFs in heterogeneous asymmetric catalysis for coupling CO2 with epoxides to obtain optically active cyclic carbonates at room temperature.
- Chen, Danping,Luo, Ran,Li, Meiyan,Wen, Mengqi,Li, Yan,Chen, Chao,Zhang, Ning
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supporting information
p. 10930 - 10933
(2017/10/11)
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- Concerning the deactivation of cobalt(III)-based porphyrin and salen catalysts in epoxide/CO2 copolymerization
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Functioning as active catalysts for propylene oxide (PO) and carbon dioxide copolymerization, cobalt(III)-based salen and porphyrin complexes have drawn great attention owing to their readily modifiable nature and promising catalytic behavior, such as high selectivity for the copolymer formation and good regioselectivity with respect to the polymer microstructure. Both cobalt(III)-salen and porphyrin catalysts have been found to undergo reduction reactions to their corresponding catalytically inactive cobalt(II) species in the presence of propylene oxide, as evidenced by UV/Vis and NMR spectroscopies and X-ray crystallography (for cobalt(II)-salen). Further investigations on a TPPCoCl (TPP=tetraphenylporphyrin) and NaOMe system reveal that such a catalyst reduction is attributed to the presence of alkoxide anions. Kinetic studies of the redox reaction of TPPCoCl with NaOMe suggests a pseudo-first order in cobalt(III)-porphyrin. The addition of a co-catalyst, namely bis(triphenylphosphine)iminium chloride (PPNCl), into the reaction system of cobalt(III)-salen/porphyrin and PO shows no direct stabilizing effect. However, the results of PO/CO2 copolymerization by cobalt(III)-salen/porphyrin with PPNCl suggest a suppressed catalyst reduction. This phenomenon is explained by a rapid transformation of the alkoxide into the carbonate chain end in the course of the polymer formation, greatly shortening the lifetime of the autoreducible PO-ring-opening intermediates, cobalt(III)-salen/porphyrin alkoxides.
- Xia, Wei,Salmeia, Khalifah A.,Vagin, Sergei I.,Rieger, Bernhard
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p. 4384 - 4390
(2015/03/14)
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- Structure and asymmetric epoxidation reactivity of chiral Mn(III) salen catalysts modified by different axial anions
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A series of chiral Mn(iii) catalysts [salen-Mn(iii)][X] (X- = Cl-, OAc-, NO3-, BF4-, CF3SO3-, OCH2CH3-) were synthesized by ion exchange. The influence of the axial anion on both the electronic structure and steric configuration of [salen-Mn(iii)][X] were carefully investigated. Besides, the reactivity and enantioselectivity of these catalysts were explored in the asymmetric epoxidation of olefins. The obtained results indicate that the axial anions have influences on both electronic structure and steric configuration of the chiral Mn(iii) salen complexes. Controlling the reactivity and enantioselectivity of these chiral Mn(iii) salen complexes can be achieved by changing the axial anions.
- Xi, Xiuxing,Shao, Jing,Hu, Xingbang,Wu, Youting
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p. 80772 - 80778
(2015/10/05)
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- SALEN INDIUM CATALYSTS AND METHODS OF MANUFACTURE AND USE THEREOF
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The present application provides salen indium catalysts of the following general structure (Formula (I)), and the corresponding dimers. The salen indium catalysts are particularly useful in catalyzing ring-opening polymerizations of cyclic ester monomers, such as lactides. Also provided herein are methods of using the salen indium complexes to catalyze polymerization of cyclic ester monomers. Of particular interest is the successful polymerization of lactides using the present salen indium catalysts to produce poly(lactic acid) having high isotacticity.
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Paragraph 00145; 00146; 00147
(2013/09/26)
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- Dual catalyst system for asymmetric alternating copolymerization of carbon dioxide and cyclohexene oxide with chiral aluminum complexes: Lewis base as catalyst activator and lewis acid as monomer activator
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Optically active aluminum complexes such as Schiff base, binuclear β-ketoiminate, and bisprolinol complexes were found to promote asymmetric alternating copolymerizations of carbon dioxide and cyclohexene oxide. The aluminum Schiff base complexes-tetraethylammonium acetate afforded isotactic poly(cyclohexene carbonate)s with low enantioselectivities. Lewis bases having two coordinating sites were utilized to enhance activity and selectivity based on the binuclear structure of the aluminum β-ketoiminate clarified by X-ray crystallography. [2gAlMe]2-bulky bisimidazole produced the alternating copolymer with high enantioselectivity (62% ee). The polymerization is considered to preferentially proceed at more crowded, enantioselective site owing to coordination of bulky Lewis bases to aluminums in less enantioselective sites. 32AlMe-2-picoline also exhibited a high enantioselectivity (67% ee). Methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) was applied to perform faster and more enantioselective copolymerizations at low temperature (82% ee). The asymmetric copolymerizations were found to be significantly dependent on size of epoxide, temperature, and kind/amount of activators.
- Nishioka, Kiyoshi,Goto, Hidetoshi,Sugimoto, Hiroshi
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p. 8172 - 8192
(2013/01/15)
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- Asymmetric cyanohydrin formation from aldehydes catalyzed by manganese Schiff base complexes
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The catalyst generated in situ from Mn(OAc)2 and a chiral Schiff base ligand exhibited excellent catalytic abilities in asymmetric cyanohydrin formation from aldehydes with sodium cyanide in up to 99% enantioselectivity and good yield.
- Qu, Yanyang,Jing, Linhai,Wu, Zhiqing,Wu, Di,Zhou, Xiangge
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experimental part
p. 187 - 190
(2010/04/28)
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- Titanium-salan-catalyzed asymmetric oxidation of sulfides and kinetic resolution of sulfoxides with H2O2 as the oxidant
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Asymmetric oxidation of sufides to sulfoxides by aqueous hydrogen peroxide with catalysis by titanium-salan complexes is presented. Optically active sulfoxides have been obtained with good to high enantioselectivities (up to 97% ee) by a tandem enantioselective oxidation and kinetic resolution procedure, the catalyst performing over 500 turnovers with no loss of enantioselectivity. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Bryliakov, Konstantin P.,Talsi, Evgenii P.
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experimental part
p. 3369 - 3376
(2009/04/07)
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- PROCESS FOR THE CYANATION OF ALDEHYDES
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The present invention relates to a process for the cyanation of aldehydes, particularly to the asymmetric cyanation of aldehydes, including the synthesis of chiral cyanohydrins and derivatives thereof, such as chiral O-acyl cyanohydrins. The process of th
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(2008/06/13)
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