93-53-8Relevant academic research and scientific papers
Chiral diphosphite-modified rhodium(0) nanoparticles: Catalyst reservoir for styrene hydroformylation
Axet, M. Rosa,Castillon, Sergio,Claver, Carmen,Philippot, Karine,Lecante, Pierre,Chaudret, Bruno
, p. 3460 - 3466 (2008)
The organometallic synthesis of rhodium nanoparticles stabilized with diphosphite ligands is described. These nanoparticles were investigated as catalysts in the styrene hydroformylation reaction, and their activity and selectivity were compared with those of similar molecular complexes. NMR spectroscopic studies performed during the course of the catalytic reaction showed that the synthesized nanoparticles are not stable and produce molecular species. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
Preparation of carbonyl rhodium polyether guanidinium ionic liquids and application in asymmetric hydroformylation based on homogeneous catalysis-biphasic separation system
Guo, Zhenmei,Liu, Baoquan,Liu, Xiangxue,Lv, Zhiguo,Wang, Ke,Zhang, Chao
, (2021)
Four carbonyl rhodium polyether guanidinium ionic liquids (Rh(CO)4-PolyGILs) were firstly synthesized by utilizing the ion exchange strategy. This protocol was achieved by introducing polyether guanidinium ionic liquids (PolyGILs) into K[Rh(CO)4]. Asymmetric hydroformylation (AHF) of styrene was employed as probe reaction to investigate the catalytic performance of the above obtained four functional ionic liquids. The AHF of styrene provided 79.00% conversion, 73.30% yield and 54% enantiomeric excess for 2-phenylpropionaldehyde ([Me(EO)16TMG][Rh(CO)4] served as catalyst, (R)-BINAP served as chiral ligand at 60°C and 2.0 MPa for 4 h). In addition, based on the unique solubility properties of the above obtained four ionic liquids, a highly effective homogeneous catalysis-biphasic separation (HCBS) system was established for the AHF. HCBS system with [Me(EO)16TMG][Rh[(R)-BINAP](CO)2] could be reused four times without significantly decrease in the activity. The structure of [Me(EO)16TMG][Rh[(R)-BINAP](CO)2] was further studied by using the density functional theory (DFT) method, which revealed that the final energy of the molecule was tending to -9460.83 eV and the presence of Ph substituent provided a chiral pocket. The presence of closed rigid chiral pocket could lead to better enantioselectivities.
Rhodium catalysed asymmetric hydroformylation with diphosphite ligands based on sugar backbones
Buisman,Martin,Vos,Klootwijk,Kramer,Van Leeuwen
, p. 719 - 738 (1995)
Chiral disphosphite ligands (PP) prepared from {(2,2'-biphenyl-1,1'-diyl), (4,4',6, 6'-tetra-t-butyl-2,2'-biphenyl-1,1'-diyl), 4,4'-di-t-butyl-6,6'-dimethoxy-2,2'-biphenyl-1,1'-diyl) and di(2-t-butyl, 6-methylphenyl)} phosphorochloridites and sugar backbones {1,2-O-isopropylidene-D-xylofuranose, methyl-2,3-O-isopropylidene-α-D-mannopyranoside and (methyl-3,6-anhydro)-α-D-mannopyranoside, α-D-glucopyranoside and β-D-galactopyranoside} have been used in the rhodium catalysed asymmetric hydroformylation of styrene. Enantioselectivities up to 64% have been obtained with stable hydridorhodium diphosphite dicarbonyl catalysts (HRhPP(CO)2). High regioselectivities (up to 97%) to the branched aldehyde were found at relatively mild reaction conditions (T = 25-40°C, 9-45 bar of syngas pressure). The solution structures of HRhPP(CO)2 catalysts have been studied by 31P and 1H NMR spectroscopy. Bidentate coordination of the diphosphite ligand to the rhodium centre takes place in a bis-equatorial way. A relation between the trigonal bipyramidal structure and the enantioselectivity of the HRhPP(CO)2 complex is found. Rigid ligands with unsuitable geometries for bidentate coordination probably coordinate as monodentates and give rise to unstable catalysts and low selectivities during catalysis.
Regio- and Diastereoselective Samarium-Mediated Allylic Benzoate Reductions
Stockdale, Trevor F.,O'Neil, Gregory W.
, p. 2267 - 2271 (2017)
A regio- and diastereoselective samarium(II)-mediated reduction of allylic benzoates is described. Yields for the reactions are generally high with diastereoselectivities up to 90:10 and in some cases only a single regioisomer was obtained. The stereoselectivity of the reaction is proposed to arise from chelation of a hydroxyl-stereocenter and starting alkene geometry, with protonation occurring intramolecularly by samarium-bound water.
Tunable furanoside diphosphite ligands. A powerful approach in asymmetric catalysis
Dieguez, Montserrat,Ruiz, Aurora,Claver, Carmen
, p. 2957 - 2963 (2003)
A series of highly tunable furanoside diphosphite ligands, derived from readily available D-(+)-xylose and D-(+)glucose, are discussed. Their modular nature allows a facile systematic variation in the configuration of the stereo-centres at the ligand bridge and in the biaryl substituents. This enabled to select a ligand for each particular reaction that provided enantioselectivities that are comparable to those of the best catalysts previously reported in different asymmetric reactions. The Royal Society of Chemistry 2003.
Diphosphite ligands based on ribose backbone as suitable ligands in the hydrogenation and hydroformylation of prochiral olefins
Pamies, Oscar,Net, Gemma,Ruiz, Aurora,Claver, Carmen
, p. 1097 - 1108 (2000)
Rh(I) and Ir(I) cationic complexes [M(cod)(PP)]BF4 have been synthesised from diphosphite ligands 4-6 derived from ribofuranose. They have been used in the rhodium and iridium catalysed asymmetric hydrogenation of acrylic acid derivatives. Ribose derivative ligands 4-6 have also been used as auxiliaries in the Rh-catalysed hydroformylation of styrene. Hydroformylation results have been explained on the basis of the species formed under hydroformylation conditions. Comparative experiments with the related epimer D-(+)-xylose derivatives showed that the configuration of the product is controlled by the absolute configuration of the stereogenic carbon atom C-3. Copyright (C) 2000 Elsevier Science Ltd.
Deracemization through photochemical E/Z isomerization of enamines
Huang, Mouxin,Luo, Sanzhong,Pan, Tianrun,Zhang, Long
, p. 869 - 874 (2022/03/07)
Catalytic deracemization of a-branched aldehydes is a direct strategy to construct enantiopure a-tertiary carbonyls, which are essential to pharmaceutical applications. Here, we report a photochemical E/Z isomerization strategy for the deracemization of a-branched aldehydes by using simple aminocatalysts and readily available photosensitizers. A variety of racemic a-branched aldehydes could be directly transformed into either enantiomer with high selectivity. Rapid photodynamic E/Z isomerization and highly stereospecific iminium/enamine tautomerization are two key factors that underlie the enantioenrichment. This study presents a distinctive photochemical E/Z isomerization strategy for externally tuning enamine catalysis.
Are Highly Stable Covalent Organic Frameworks the Key to Universal Chiral Stationary Phases for Liquid and Gas Chromatographic Separations?
Cui, Yong,Jia, Wenyan,Li, Yanan,Yu, Ziyun,Yuan, Chen,Yuan, Li-Ming,Zi, Min
, p. 891 - 900 (2022/02/03)
High-performance liquid chromatography (HPLC) and gas chromatography (GC) over chiral stationary phases (CSPs) represent the most popular and highly applicable technology in the field of chiral separation, but there are currently no CSPs that can be used for both liquid and gas chromatography simultaneously. We demonstrate here that two olefin-linked covalent organic frameworks (COFs) featuring chiral crown ether groups can be general CSPs for extensive separation not only in GC but also in normal-phase and reversed-phase HPLC. Both COFs have the same 2D layered porous structure but channels of different sizes and display high stability under different chemical environments including water, organic solvents, acids, and bases. Chiral crown ethers are periodically aligned within the COF channels, allowing for enantioselective recognition of guest molecules through intermolecular interactions. The COF-packed HPLC and GC columns show excellent complementarity and each affords high resolution, selectivity, and durability for the separation of a wide range of racemic compounds, including amino acids, esters, lactones, amides, alcohols, aldehydes, ketones, and drugs. The resolution performances are comparable to and the versatility is superior to those of the most widely used commercial chiral columns, showing promises for practical applications. This work thus advances COFs with high stability as potential universal CSPs for chromatography that are otherwise hard or impossible to produce.
Asymmetric Hydroformylation Using a Rhodium Catalyst Encapsulated in a Chiral Capsule
Jongkind, Lukas J.,Reek, Joost N. H.
, p. 867 - 875 (2020/03/03)
Supramolecular capsules can be used to change the activity and selectivity of a catalyst through the influence of the second coordination sphere, reminiscent of how enzymes control the selectivity of their processes. In enzymes, this approach is used to also control the enantioselectivity of reactions in which the active catalytic site is often not chiral but the second coordination sphere is. We are interested in the possibility to generate a chiral second coordination sphere around an otherwise achiral transition metal complex for asymmetric catalysis. In this paper we show that the ligand template approach can be used to generate a chiral second coordination sphere around a rhodium complex, which is used in asymmetric hydroformylation.
Diaza-Crown Ether-Bridged Chiral Diphosphoramidite Ligands: Synthesis and Applications in Asymmetric Catalysis
Luo, Yier,Ouyang, Guanghui,Tang, Yuping,He, Yan-Mei,Fan, Qing-Hua
, p. 8176 - 8184 (2020/07/15)
A small library of diaza-crown ether-bridged chiral diphosphoramidite ligands was prepared. In the rhodium-catalyzed asymmetric hydrogenation and hydroformylation reactions, these ligands exhibited distinct properties in catalytic activity and/or enantioselectivity. Hydrogenated products with opposite absolute configurations could be obtained in high yields with excellent ee values by utilizing (S,S)-L1 and (S,S)-L3, respectively. Meanwhile, the addition of alkali metal cations caused variations in catalytic outcomes, showing the supramolecular tunability of these Rh/diphosphoramidite catalytic systems.
