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Chiral diphosphite-modified rhodium(0) nanoparticles: Catalyst reservoir for styrene hydroformylation
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.
Axet, M. Rosa,Castillon, Sergio,Claver, Carmen,Philippot, Karine,Lecante, Pierre,Chaudret, Bruno
p. 3460 - 3466
(2008)
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Preparation of carbonyl rhodium polyether guanidinium ionic liquids and application in asymmetric hydroformylation based on homogeneous catalysis-biphasic separation system
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.
Guo, Zhenmei,Liu, Baoquan,Liu, Xiangxue,Lv, Zhiguo,Wang, Ke,Zhang, Chao
(2021)
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Rhodium catalysed asymmetric hydroformylation with diphosphite ligands based on sugar backbones
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.
Buisman,Martin,Vos,Klootwijk,Kramer,Van Leeuwen
p. 719 - 738
(1995)
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Regio- and Diastereoselective Samarium-Mediated Allylic Benzoate Reductions
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.
Stockdale, Trevor F.,O'Neil, Gregory W.
p. 2267 - 2271
(2017)
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Tunable furanoside diphosphite ligands. A powerful approach in asymmetric catalysis
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.
Dieguez, Montserrat,Ruiz, Aurora,Claver, Carmen
p. 2957 - 2963
(2003)
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Diphosphite ligands based on ribose backbone as suitable ligands in the hydrogenation and hydroformylation of prochiral olefins
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.
Pamies, Oscar,Net, Gemma,Ruiz, Aurora,Claver, Carmen
p. 1097 - 1108
(2000)
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Deracemization through photochemical E/Z isomerization of enamines
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.
Huang, Mouxin,Luo, Sanzhong,Pan, Tianrun,Zhang, Long
p. 869 - 874
(2022/03/07)

Are Highly Stable Covalent Organic Frameworks the Key to Universal Chiral Stationary Phases for Liquid and Gas Chromatographic Separations?
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.
Cui, Yong,Jia, Wenyan,Li, Yanan,Yu, Ziyun,Yuan, Chen,Yuan, Li-Ming,Zi, Min
p. 891 - 900
(2022/02/03)

Diaza-Crown Ether-Bridged Chiral Diphosphoramidite Ligands: Synthesis and Applications in Asymmetric Catalysis
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.
Luo, Yier,Ouyang, Guanghui,Tang, Yuping,He, Yan-Mei,Fan, Qing-Hua
p. 8176 - 8184
(2020/07/15)

Chelation and Stereodirecting Group Effects on Regio- And Diastereoselective Samarium(II)-Water Allylic Benzoate Reductions
SmI 2 (H 2 O) n reductions of allylic benzoates adjacent to a trisubstituted alkene occur in high yields with complete regioselectivity and good diastereoselectivity (up to 90:10) for substrates containing properly positioned stereodirecting- and chelating groups. The outcome of these reactions can be rationalized by ring conformation considerations of a proposed chelated organosamarium intermediate, and a mechanism involving intramolecular protonation by a samarium-bound water.
Leitch, Michael A.,O'Neil, Gregory W.,Stockdale, Trevor F.
p. 1544 - 1560
(2020/05/19)

Asymmetric Hydroformylation Using a Rhodium Catalyst Encapsulated in a Chiral Capsule
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.
Jongkind, Lukas J.,Reek, Joost N. H.
p. 867 - 875
(2020/03/03)

Rhodium-Catalyzed Remote C(sp3)?H Borylation of Silyl Enol Ethers
A rhodium-catalyzed remote C(sp3)?H borylation of silyl enol ethers (SEEs, E/Z mixtures) by alkene isomerization and hydroboration is reported. The reaction exhibits mild reaction conditions and excellent functional-group tolerance. This method is compatible with an array of SEEs, including linear and branched SEEs derived from aldehydes and ketones, and provides direct access to a broad range of structurally diverse 1,n-borylethers in excellent regioselectivities and good yields. These compounds are precursors to various valuable chemicals, such as 1,n-diols and aminoalcohols.
Li, Jie,Qu, Shuanglin,Zhao, Wanxiang
supporting information
p. 2360 - 2364
(2020/01/02)

Synthesis and characterization of tetracarbonylmolybdenum(0) and pentacarbonyltungsten(0) complexes of TADDOL-derived, monodentate P-donor ligands
TADDOL-derived P-donor ligands are of interest as ligands in transition metal catalyzed transformations; however, few studies have been conducted on the steric and electronic properties of P-donor ligands derived from TADDOL. To gain more insight into these properties four tetracarbonylmolybdenum(0) and two pentacarbonyltungsten(0) complexes of monodentate P-donor ligands derived from TADDOL have been studied. These studies show that exchanging the chloro substituent on the phosphorus for OMe increases the donor ability of the ligand and that the cis-tetracarbonylmolybdenum(0) complex of the ligand having the OMe substituent spontaneously isomerizes in solution. X-ray crystallographic analyses indicate that the orientations of the 1,3,2-dioxaphosphepane ring and the aryl substituents are not always conserved, even within the same complex.
Cagle, Ethan C.,Gray, Gary M.
p. 130 - 138
(2019/01/03)

3-BocNH-ABNO-catalyzed aerobic oxidation of alcohol at room temperature and atmospheric pressure
A transition-metal-free catalytic system has been developed for selective transformation of alcohol to aldehydes or ketones. The reactions were performed with 3-(tert-butoxycarbonylamino)-9-azabicyclo[3.3.1]nonane N-oxyl (3-BocNH-ABNO) as the catalyst, NaNO2 as the co-catalyst, molecular oxygen as the terminal oxidant, and AcOH as the solvent under room temperature. This catalytic system exhibited broad functional group tolerance. A series of alcohol substrates, including primary and secondary benzylic alcohols, heteroaromatic analogues, primary and secondary aliphatic alcohols, could be converted into their corresponding aldehydes and ketones in good conversions and selectivities.
Zhao, Yajing,Li, Yutong,Shen, Zhenlu,Hu, Xinquan,Hu, Baoxiang,Jin,Sun, Nan,Li, Meichao
supporting information

(2019/08/06)

Effector enhanced enantioselective hydroformylation
In this communication, we report rhodium DIMPhos complexes with an integrated DIM-receptor that can bind carboxylate containing effectors and their application in the rhodium catalyzed hydroformylation reaction. The binding of chiral effectors in non-chiral [Rh(DIMPhos)] catalysts does not lead to enantioselective hydroformylation, but the binding of either achiral or chiral effectors can significantly enhance the enantioselectivity induced by the chiral Rh-metal complexes. For example, the supramolecular complex [Rh]/[1S?L3] displays high regio- and enantioselectivity in the hydroformylation of vinyl acetate (72% ee, and b/l >99), whereas in absence of this effector the ee is around 17%.
Bai, Shao-Tao,Kluwer, Alexander M.,Reek, Joost N. H.
supporting information
p. 14151 - 14154
(2019/12/02)

Mild Iridium-Catalysed Isomerization of Epoxides. Computational Insights and Application to the Synthesis of β-Alkyl Amines
The isomerization of epoxides to aldehydes using the readily available Crabtree's reagent is described. The aldehydes were transformed into synthetically useful amines by a one-pot reductive amination using pyrrolidine as imine-formation catalyst. The reactions worked with low catalyst loadings in very mild conditions. The procedure is operationally simple and tolerates a wide range of functional groups. A DFT study of its mechanism is presented showing that the isomerization takes place via an iridium hydride mechanism with a low energy barrier, in agreement with the mild reaction conditions. (Figure presented.).
Cabré, Albert,Cabezas-Giménez, Juanjo,Sciortino, Giuseppe,Ujaque, Gregori,Verdaguer, Xavier,Lledós, Agustí,Riera, Antoni
p. 3624 - 3631
(2019/07/10)

Novel MOP-type H8-binaphthyl monodentate phosphite ligands and their applications in transition metal-catalyzed asymmetric 1,4-conjugate additions and hydroformylations
A new series of monodentate phosphites based on the rigid, axially chiral monoesterified H8-BINOL, which are easy to prepare from the readily accessible phosphorylating reagents (Sa)- or (Ra)-1,1′-binaphthyl-2,2′-diylchlorophosphite and (Sa)- or (Ra)-1,1′-H8-binaphthyl-2,2′-diylchlorophosphite, have been synthesized. All ligands were purified on a silica gel column under a nitrogen atmosphere with moderate yields, and were white solids and air-stable at room temperature. These ligands afforded good to excellent enantioselectivities in the Cu-catalyzed 1,4-conjugate addition of 2-cyclohexenone with nucleophiles Et2Zn (96% ee) and with Ph2Zn (65% ee), 2-cyclopentenone with Et2Zn (95% ee), 2-cycloheptenone with Et2Zn (76% ee), and 5,6-dihydro-2H-pyran-2-one with Et2Zn (90% ee). In the Rh-catalyzed asymmetric hydroformylation of styrene, these ligands showed a chemoselectivity of >99% in aldehydes, and a satisfactory branched over linear ratio (96/4). Moreover, the sense of the enantiodiscrimination of the products was mainly determined by the configuration of the BINOL-based or H8-BINOL-based phosphocycle.
Tian, Mi,Pang, Zeng-bo,Li, Hai-feng,Wang, Lai-lai
supporting information
p. 330 - 337
(2017/02/18)

Porous Rh/BINAP polymers as efficient heterogeneous catalysts for asymmetric hydroformylation of styrene: Enhanced enantioselectivity realized by flexible chiral nanopockets
A new chiral monomer, (S)-5,5′-divinyl-BINAP, was successfully synthesized and embedded into two different porous organic polymers (Poly-1 and Poly-2). After loading a Rh species, the catalysts were applied for the heterogeneous asymmetric hydroformylation of styrene. Compared with the homogeneous BINAP analogue, the enantioselectivity of Rh/Poly-1 catalyst was drastically increased by approximately 70%. The improved enantioselectivity of the porous Rh/BINAP polymers was attributed to the presence of flexible chiral nanopockets resulting from the increased bulk of the R groups near the catalytic center.
Wang, Tao,Wang, Wenlong,Lyu, Yuan,Xiong, Kai,Li, Cunyao,Zhang, Hao,Zhan, Zhuangping,Jiang, Zheng,Ding, Yunjie
p. 691 - 698
(2017/04/24)

Rhodium-catalyzed hydroformylation in γ-valerolactone as a biomass-derived solvent
Rhodium-catalyzed hydroformylation of styrene, α-methylstyrene, dimethyl itaconate, and (R)-limonene was performed in gamma-valerolactone (GVL) as a proposed biomass-based environmentally benign solvent for hydroformylation referring to toluene as a generally used conventional solvent. Both achiral (triphenylphosphine, 1,3-bis(diphenylphoshino)propane) and enantiopure bidentate phosphine ligands ((S,S)-BDPP, (R)-BINAP, (R)-QUINAP, (R,R)-DIOP, (Rc),(Sp)-JOSIPHOS, (S)-SEGPHOS, (S)-(DM)-SEGPHOS) were investigated in in situ generated Rh-diphosphine catalyst systems. In general, the catalysts' activity in GVL was lower than in toluene; however, remarkable chemo- (>99%) and regioselectivities (>95%) were achieved in GVL under identical conditions. The BDPP-modified Rh-catalyst was recycled for three consecutive cycles; however a decrease in its activity was detected.
Pongrácz, Péter,Bartal, Brigitta,Kollár, László,Mika, László T.
p. 140 - 145
(2017/09/12)

Ligand effects in rhodium-catalyzed hydroformylation with bisphosphines: Steric or electronic?
Twelve commercially available bisphosphine ligands have been evaluated in rhodium-catalyzed hydroformylation reactions. All ligands exhibited high chemoselectivities for aldehyde formation. The highest enantioselectivity (53% ee) of styrene hydroformylation was achieved with (S)-BTFM-Garphos (L7) substituted with electron withdrawing substituents. High pressure NMR (HP-NMR) spectroscopy and in situ high pressure IR spectroscopy (HP-IR) were used to study the resting states of the catalyst species in the reactions. The ligand effect on the structures of the observable species was examined. Both electronic and steric factors were considered to contribute to the performance of the various ligands. The results showed that decreasing the phosphine basicity increased the enantioselectivity, while in the systems studied here the steric character plays a less important role than the electronic features in achieving good regioselectivities.
Jiao, Yunzhe,Torne, Marta Serrano,Gracia, Jose,Niemantsverdriet,Van Leeuwen, Piet W. N. M.
p. 1404 - 1414
(2017/05/05)

Rhodium-Catalyzed Asymmetric Synthesis of β-Branched Amides
A general asymmetric route for the one-step synthesis of chiral β-branched amides is reported through the highly enantioselective isomerization of allylamines, followed by enamine exchange, and subsequent oxidation. The enamine exchange allows for a rapid and modular synthesis of various amides, including challenging β-diaryl and β-cyclic.
Wu, Zhao,Laffoon, Joshua D.,Nguyen, Trang T.,McAlpin, Jacob D.,Hull, Kami L.
supporting information
p. 1371 - 1375
(2017/01/24)

Catalytic asymmetric [4+2]-cycloaddition of dienes with aldehydes
Despite its significant potential, a general catalytic asymmetric [4+2]-cycloaddition of simple and electronically unbiased dienes with any type of aldehyde has long been unknown. Previously developed methodologies invariably require activated, electronically engineered substrates. We now provide a general solution to this problem. We show that highly acidic and confined imidodiphosphorimidates (IDPis) are extremely effective Br?nsted acid catalysts of the hetero-Diels-Alder reaction of a wide variety of aldehydes and dienes to give enantiomerically enriched dihydropyrans. Excellent stereoselectivity is generally observed and a variety of scents and natural products can be easily accessed.
Liu, Luping,Kim, Hyejin,Xie, Youwei,Fares, Christophe,Kaib, Philip S.J.,Goddard, Richard,List, Benjamin
supporting information
p. 13656 - 13659
(2017/11/06)

Highly Efficient Oxidation of Amines to Aldehydes with Flow-based Biocatalysis
A new mild and efficient process for the aqueous preparation of aldehydes, which are employed as flavour and fragrance components in food, beverage, cosmetics, as well as in pharmaceuticals, was developed using a continuous-flow approach based on an immobilised pure transaminase-packed bed reactor. HEWT, an ω-transaminase from the haloadapted bacterium Halomonas elongata, has been selected for its excellent stability and substrate scope. Sixteen different amines were rapidly (3–15 min) oxidised to the corresponding aldehydes (90 to 99 %) with only 1 to 5 equivalents of sodium pyruvate. The process was fully automated, allowing for the in-line recovery of the pure aldehydes (chemical purity >99 % and isolated yields above 80 %), without any further work-up procedure.
Contente, Martina L.,Dall'Oglio, Federica,Tamborini, Lucia,Molinari, Francesco,Paradisi, Francesca
p. 3843 - 3848
(2017/09/25)

Anti-Markovnikov alkene oxidation by metal-oxo–mediated enzyme catalysis
Catalytic anti-Markovnikov oxidation of alkene feedstocks could simplify synthetic routes to many important molecules and solve a long-standing challenge in chemistry. Here we report the engineering of a cytochrome P450 enzyme by directed evolution to catalyze metal-oxo–mediated anti-Markovnikov oxidation of styrenes with high efficiency. The enzyme uses dioxygen as the terminal oxidant and achieves selectivity for anti-Markovnikov oxidation over the kinetically favored alkene epoxidation by trapping high-energy intermediates and catalyzing an oxo transfer, including an enantioselective 1,2-hydride migration. The anti-Markovnikov oxygenase can be combined with other catalysts in synthetic metabolic pathways to access a variety of challenging anti-Markovnikov functionalization reactions.
Hammer, Stephan C.,Kubik, Grzegorz,Watkins, Ella,Huang, Shan,Minges, Hannah,Arnold, Frances H.
p. 215 - 218
(2017/10/19)

Biocatalytic Formal Anti-Markovnikov Hydroamination and Hydration of Aryl Alkenes
Biocatalytic anti-Markovnikov alkene hydroamination and hydration were achieved based on two concepts involving enzyme cascades: epoxidation-isomerization-amination for hydroamination and epoxidation-isomerization-reduction for hydration. An Escherichia coli strain coexpressing styrene monooxygenase (SMO), styrene oxide isomerase (SOI), ω-transaminase (CvTA), and alanine dehydrogenase (AlaDH) catalyzed the hydroamination of 12 aryl alkenes to give the corresponding valuable terminal amines in high conversion (many ≥86%) and exclusive anti-Markovnikov selectivity (>99:1). Another E. coli strain coexpressing SMO, SOI, and phenylacetaldehyde reductase (PAR) catalyzed the hydration of 12 aryl alkenes to the corresponding useful terminal alcohols in high conversion (many ≥80%) and very high anti-Markovnikov selectivity (>99:1). Importantly, SOI was discovered for stereoselective isomerization of a chiral epoxide to a chiral aldehyde, providing some insights on enzymatic epoxide rearrangement. Harnessing this stereoselective rearrangement, highly enantioselective anti-Markovnikov hydroamination and hydration were demonstrated to convert α-methylstyrene to the corresponding (S)-amine and (S)-alcohol in 84-81% conversion with 97-92% ee, respectively. The biocatalytic anti-Markovnikov hydroamination and hydration of alkenes, utilizing cheap and nontoxic chemicals (O2, NH3, and glucose) and cells, provide an environmentally friendly, highly selective, and high-yielding synthesis of terminal amines and alcohols.
Wu, Shuke,Liu, Ji,Li, Zhi
p. 5225 - 5233
(2017/08/17)

Catalyst-Controlled Multicomponent Aziridination of Chiral Aldehydes
A highly diastereoselective and enantioselective method for the multicomponent aziridination of chiral aldehydes has been developed with BOROX catalysts of the VANOL (3,3′-diphenyl-2,2′-bi-1-naphthol) and VAPOL (2,2′-diphenyl-(4-biphenanthrol)) ligands. Very high to perfect catalyst control is observed with most all substrates examined including aldehydes with chiral centers in the α- and β-positions. High catalyst control was also observed for a number of chiral heterocyclic aldehydes allowing for the preparation of epoxy aziridines, bis(aziridines) and ethylene diaziridines. Application of this reaction in the synthesis of β3-homo-d-alloisoleucine and β3-homo-l-isoleucine is reported.
Mukherjee, Munmun,Zhou, Yubai,Dai, Yijing,Gupta, AniL K.,Pulgam, V. Reddy,Staples, Richard J.,Wulff, William D.
supporting information
p. 2552 - 2556
(2017/03/06)

A step towards hydroformylation under sustainable conditions: Platinum-catalysed enantioselective hydroformylation of styrene in gamma-valerolactone
Platinum-catalysed enantioselective hydroformylation of styrene was performed in γ-valerolactone (GVL) as a proposed environmentally benign reaction medium. Optically active bidentate ligands, possessing various types of chirality elements e.g. central (B
Pongrácz, Péter,Kollár, László,Mika, László T.
p. 842 - 847
(2016/02/12)

Continuous Liquid Vapor Reactions Part 1: Design and Characterization of a Reactor for Asymmetric Hydroformylation
A research scale continuous reactor system was designed and developed for high pressure asymmetric hydroformylation (AHF) reactions with an 8 h reaction time. The continuous reactor achieved high kLa, low axial dispersion, and an 8 mL liquid holdup volume. The reactor consisted of 20 vertical bubble flow pipes-in-series, connected by small diameter tubing jumpers. This type of continuous reactor is proven to be scalable up to 360 L in our GMP pharmaceutical manufacturing plant for high pressure hydrogenation. The continuous reactor was used for the AHF of styrene and 2-vinyl-6-methoxynaphthalene catalyzed by rhodium(bisdiazaphospholane) (BDP) complexes. The CSTRs-in-series numerical model fit the experimental data better than the plug flow with dispersion model. Samples were taken along the length of the continuous reactor and used for kinetic data modeling. Vapor liquid mass transfer rate constants were about 3 orders of magnitude higher than reaction rate constants.
Johnson, Martin D.,May, Scott A.,Calvin, Joel R.,Lambertus, Gordon R.,Kokitkar, Prashant B.,Landis, Clark R.,Jones, Bradley R.,Abrams, M. Leigh,Stout, James R.
p. 888 - 900
(2016/06/13)

A comparison of MOP-phosphonite ligands and their applications in Rh(i)- and Pd(II)-catalysed asymmetric transformations
Six chiral MOP-phosphonites have been synthesised and compared via experimental and computational methods in an effort to quantify their differing structural and electronic profiles. They were found to be electron-poor ligands in comparison to their arylphosphine analogues and have a larger trans influence in square planar Pt(ii) complexes. Four [Rh(LP)(η2:η2-cod)Cl] complexes were synthesised and characterised by NMR, HRMS and X-ray crystallography. Two [Rh(LP)2]BF4 complexes were prepared where one ligand acts as a chelating P,C-π-donor; detailed NMR studies demonstrated a hemilabile η6-coordination mode, which in one case was confirmed by X-ray crystallography. Rh(i) complexes were used as catalysts in asymmetric hydrogenation and hydroformylation reactions and in the addition of phenyl boronic acid to an isatin. Pd(ii) complexes were successfully employed in asymmetric Suzuki-Miyaura cross-coupling reactions yielding binaphthyl products. Two [Pd(LP)2Cl2] complexes were synthesised and characterised by X-ray crystallography, both adopting cis orientations, with one of the complexes crystallising as two pseudo-polymorphs.
Fleming, James T.,Wills, Corinne,Waddell, Paul G.,Harrington, Ross W.,Higham, Lee J.
supporting information
p. 15660 - 15670
(2016/10/13)

KetoABNO/NOx Cocatalytic Aerobic Oxidation of Aldehydes to Carboxylic Acids and Access to α-Chiral Carboxylic Acids via Sequential Asymmetric Hydroformylation/Oxidation
A method for aerobic oxidation of aldehydes to carboxylic acids has been developed using organic nitroxyl and NOx cocatalysts. KetoABNO (9-azabicyclo[3.3.1]nonan-3-one N-oxyl) and NaNO2 were identified as the optimal nitroxyl and NOx sources, respectively. The mildness of the reaction conditions enables sequential asymmetric hydroformylation of alkenes/aerobic aldehyde oxidation to access α-chiral carboxylic acids without racemization. The scope, utility, and limitations of the oxidation method are further evaluated with a series of achiral aldehydes bearing diverse functional groups.
Miles, Kelsey C.,Abrams, M. Leigh,Landis, Clark R.,Stahl, Shannon S.
supporting information
p. 3590 - 3593
(2016/08/16)

Synthesis, Characterization, and Application of Platinum(II) Complexes Incorporating Racemic and Optically Active 4-Chloro-5-Methyl-1-Phenyl-1,2,3,6-Tetrahydrophosphinine Ligand
An efficient resolution method was elaborated for the preparation of (+)-4-chloro-5-methyl-1-phenyl-1,2,3,6-tetrahydrophosphinine oxide using the acidic Ca2+ salt of (-)-O,O-di-p-toluoyl-(2R,3R)-tartaric acid. Crystal structure of the diastereo
Bagi, Péter,Karaghiosoff, Konstantin,Czugler, Mátyás,Hessz, Dóra,Kállay, Mihály,Kubinyi, Miklós,Szilvási, Tibor,Pongrácz, Péter,Kollár, László,Timári, István,K?vér, Katalin E.,Drahos, László,Fogassy, Elemér,Keglevich, Gy?rgy
p. 91 - 101
(2016/04/04)

Enantioselective hydroformylation of 2- and 4-substituted styrenes with PtCl2[(R)-BINAP] + SnCl2‘in situ’ catalyst
Two sets of styrenes possessing various substituents either in ortho or para position were hydroformylated in the presence of ‘in situ’ catalyst formed from PtCl2[(R)-BINAP] and tin(II) chloride. The reversal of the absolute configuration of the preferred enantiomers was observed using both sets of substrates by the variation of the reaction temperature in the range of 40–100 °C. In case of the 4-substituted styrenes, the reversal temperature of the enantioselectivity shows correlation with the Hammett substituent constants, i.e., with the electron donor or electron acceptor properties of the para-substituents. This phenomenon was explained by the reversible formation of the Pt-branched alkyl intermediates, leading to the corresponding (R)- and (S)-enantiomers of 2-arylpropanals. Strong substituent effect on the regioselectivity was observed in the hydroformylation of 2-substituted styrenes: the presence of substituents characterised by larger steric parameter resulted in the highly favoured formation of the linear aldehyde. For instance, regioselectivities of 45%, 22% and 7% towards branched aldehyde were obtained with styrene, 2-fluoro- and 2-bromostyrene, respectively, at 80 °C reaction temperature. In addition to the characteristic change of regioselectivity, the reversal of absolute configuration as a function of reaction temperature was also observed.
Pongrácz, Péter,Kollár, László
p. 118 - 123
(2016/10/25)

Enantioselective hydroformylation by a Rh-catalyst entrapped in a supramolecular metallocage
Regio- and enantioselective hydroformylation of styrenes is attained upon embedding a chiral Rh complex in a nonchiral supramolecular cage formed from coordination-driven self-assembly of macrocyclic dipalladium complexes and tetracarboxylate zinc porphyrins. The resulting supramolecular catalyst converts styrene derivatives into aldehyde products with much higher chiral induction in comparison to the nonencapsulated Rh catalyst. Spectroscopic analysis shows that encapsulation does not change the electronic properties of the catalyst nor its first coordination sphere. Instead, enhanced enantioselectivity is rationalized by the modification of the second coordination sphere occurring upon catalyst inclusion inside the cage, being one of the few examples in achieving an enantioselective outcome via indirect through-space control of the chirality around the catalyst center. This effect resembles those taking place in enzymatic sites, where structural constraints imposed by the enzyme cavity can impart stereoselectivities that cannot be attained in bulk. These results are a showcase for the future development of asymmetric catalysis by using size-tunable supramolecular capsules.
Garca-Simn, Cristina,Gramage-Doria, Rafael,Raoufmoghaddam, Saeed,Parella, Teodor,Costas, Miquel,Ribas, Xavi,Reek, Joost N. H.
p. 2680 - 2687
(2015/03/04)

Supramolecularly Regulated Ligands for Asymmetric Hydroformylations and Hydrogenations
Herein we report the use of polyether binders as regulation agents (RAs) to enhance the enantioselectivity of rhodium-catalyzed transformations. For reactions of diverse substrates mediated by rhodium complexes of the α,ω-bisphosphite-polyether ligands 1-5,a-d, the enantiomeric excess (ee) of hydroformylations was increased by up to 82 (substrate: vinyl benzoate, 96ee), and the ee value of hydrogenations was increased by up to 5 (substrate: N-(1-(naphthalene-1-yl)vinyl)acetamide, 78ee). The ligand design enabled the regulation of enantioselectivity by generation of an array of catalysts that simultaneously preserve the advantages of a privileged structure in asymmetric catalysis and offer geometrically close catalytic sites. The highest enantioselectivities in the hydroformylation of vinyl acetate with ligand 4b were achieved by using the Rb[B(3,5-(CF3)2C6H3)4] (RbBArF) as the RA. The enantioselective hydrogenation of the substrates 10 required the rhodium catalysts derived from bisphosphites 3a or 4a, either alone or in combination with different RAs (sodium, cesium, or (R,R)-bis(1-phenylethyl)ammonium salts). This design approach was supported by results from computational studies.
Vidal-Ferran, Anton,Mon, Ignasi,Bauzá, Antonio,Frontera, Antonio,Rovira, Laura
supporting information
p. 11417 - 11426
(2015/08/03)

Metal Complexes Containing Enantiopure Bis(diamidophosphite) Ligands in Asymmetric Allylic Substitution and Hydroformylation Reactions
Enantiopure bis(diamidophosphite) ligands with a heterocyclic terminal fragment derived from (R)- and (S)-N,N′-dimethyl-1,1′-binaphthyldiamine and bridging fragments derived from (S,S)-2,3-butanediol (a), (4R,5R)-4,5-di(hydroxymethyl)-2,2-dimethyl-1,3-dioxolane (b), and (R)- and (S)-1,1′-bi-2-naphthol (c) were used to prepare the palladium complexes with general formula [Pd(η3-2-CH3-C3H4)(P-P)][X] (X = PF6, 1a-(S;Sal,Sal;S), 1b-(R;Ral,Ral;R), 1b-(S;Ral,Ral;S), 1c-(R;Ral;R), 1c-(R;Sal;R); X = BPh4, 2a-(R;Sal,Sal;R), 2c-(R;Ral;R)), which have been fully characterized. The solid-state structure for complexes 1a-(S;Sal,Sal;S) and 1b-(R;Ral,Ral;R) has been determined by X-ray diffraction. The catalytic performance of the palladium complexes has been evaluated in asymmetric allylic alkylation and amination reactions with the benchmark substrate. The influence of the nature and absolute configuration of both the terminal and bridging fragments of the bis(diamidophosphite) ligands on the asymmetric induction is discussed. The best results in terms of enantioselectivity were obtained with 1c-(R;Ral;R), affording enantiomeric excesses up to 85% in both alkylation and amination reactions. A large match-mismatch effect between the absolute configurations of stereocenters of ligand c has been observed in the allylic amination process. Preliminary results in the rhodium-catalyzed asymmetric hydroformylation of styrene by using bis(diamidophosphite) ligands a, b, and c disclosed in all cases low enantiomeric discrimination for the branched aldehyde. Both for the allylic alkylation and for the hydroformylation reaction, a related monodentate diamidophosphite d, derived from (R)-N,N′-dimethyl-1,1′-binaphthyldiamine and (S)-borneol, was also tested. Palladium complexes of this monodentate ligand showed fairly good enantioselectivity in allylic alkylation, but with very low rate, while the rhodium complex of d rendered better enantioselectivity (37% ee) than the bidentate ligands a-c in the hydroformylation of styrene. (Figure Presented).
Bravo, Maritza J.,Ceder, Rosa M.,Grabulosa, Arnald,Muller, Guillermo,Rocamora, Merc,Bayn, J. Carles,Peral, Daniel
p. 3799 - 3808
(2015/08/24)

Asymmetric Hydroformylation of Heterocyclic Olefins Mediated by Supramolecularly Regulated Rhodium-Bisphosphite Complexes
Rhodium complexes derived from conformationally transformable α,ω-bisphosphite ligands combined with a suitable alkali metal BArF salt as a regulation agent (RA) provide high regio- and enantioselectivities in the asymmetric hydroformylation (AHF) of three heterocyclic olefins. The outcome of the AHF could be exquisitely regulated by choosing the appropriate RA with an increase in the ee, the reversal of the regioselectivity, or the complete suppression of one byproduct.
Rovira, Laura,Vaquero, Mónica,Vidal-Ferran, Anton
supporting information
p. 10397 - 10403
(2015/11/03)

Accessible protocol for asymmetric hydroformylation of vinylarenes using formaldehyde
We report herein on an accessible protocol for the asymmetric hydroformylation of vinylarenes using formaldehyde as a substitute for syngas. The regioselectivity (branched/linear = up to 96/4) and enantioselectivity (up to 95% ee) can be attributed to the use of chiral Ph-bpe as a ligand. This journal is
Morimoto, Tsumoru,Fujii, Tetsuji,Miyoshi, Kota,Makado, Gouki,Tanimoto, Hiroki,Nishiyama, Yasuhiro,Kakiuchi, Kiyomi
supporting information
p. 4632 - 4636
(2015/04/27)

Easily accessible TADDOL-derived bisphosphonite ligands: Synthesis and application in the asymmetric hydroformylation of vinylarenes
The synthesis of chiral bidentate bisphosphonite ligands based on the TADDOL motif from readily available starting materials has been developed. Taking advantage of the modular nature of the building blocks, a diverse ligand library has been prepared. Their catalytic potential has been evaluated in the asymmetric hydroformylation of styrene and derivatives. These catalysts showed high activity and provided the aldehydes in high enantiomeric purity.
Allmendinger, Simon,Kinuta, Hirotaka,Breit, Bernhard
supporting information
p. 41 - 45
(2015/03/03)

A study on the optical resolution of 1-isopropyl-3-methyl-3-phospholene 1-oxide and its use in the synthesis of borane and platinum complexes
A 1-isopropyl-3-phospholene 1-oxide was prepared and the two enantiomers were isolated from the racemate by resolution using optically active TADDOL derivatives or the acidic Ca2+ salts of (-)-O,O-diaroyl-(2R,3R)-tartaric acids. The single crystal X-ray structure of the 1-isopropyl-3-phospholene oxide - spiro-TADDOL 1:2 associate revealed the mode of binding between the host and guest molecules. The role of the interactions between the three molecules was supported not only by the contact data, but also force field and semiempirical calculations. Beside X-ray analysis, the absolute configuration of the P-stereogenic center was also determined on the basis of CD spectroscopy and high level quantum chemical calculations. The racemic and optically active 1-isopropyl-3-phospholenes obtained after deoxygenation were converted to the corresponding borane complexes and Pt(II) complexes. Stereostructure of the latter species was evaluated by high level quantum chemical calculations and the Pt complexes were tested as catalysts in the hydroformylation of styrene.
Bagi, Péter,Juhász, Kinga,Timári, István,K?vér, Katalin E.,Mester, Dávid,Kállay, Mihály,Kubinyi, Miklós,Szilvási, Tibor,Pongrácz, Péter,Kollár, László,Karaghiosoff, Konstantin,Czugler, Mátyás,Drahos, László,Fogassy, Elemér,Keglevich, Gy?rgy
p. 140 - 152
(2015/09/15)

Exploring the synthetic applicability of a new carboxylic acid reductase from Segniliparus rotundus DSM 44985
A new carboxylic acid reductase (CAR) gene from Segniliparus rotundus DSM 44985 was overexpressed in Escherichia coli. The recombinant enzyme exhibited high activity toward a variety of aromatic and aliphatic carboxylic acids. Especially, it effectively reduced 4-hydroxybenzoic acid (8a) and 4-nitrobenzoic acid (19a), toward which the known Nocardia CAR exhibited no or little activity. The recombinant E. coli cells co-expressing the Segniliparus CAR and Nocardia PPTase genes catalyzed the reductions of vanillic acid (20a) and 3,4-dihydroxyphenylacetic acid (25a) to give vanillyl alcohol (20c) and 3-hydroxytyrosol (25c) with high yield, respectively. The endogenous aldehyde reductases of E. coli should be responsible for the further reduction of the produced aldehydes. These results demonstrated that Segniliparus CAR was a useful addition to the biocatalyst tool-box for the reduction of carboxylic acids and might find applications in the synthesis of valuable bio-based chemicals from renewable resources.
Duan, Yitao,Yao, Peiyuan,Chen, Xi,Liu, Xiangtao,Zhang, Rui,Feng, Jinhui,Wu, Qiaqing,Zhu, Dunming
p. 1 - 7
(2015/02/19)

Rhodium/phospholane-phosphite catalysts give unusually high regioselectivity in the enantioselective hydroformylation of vinyl arenes
Using the phospholane-phosphite ligand, BOBPHOS, almost perfect regioselectivities and high enantioselectivities (up to 92% ee) are observed in Rh catalysed enantioselective hydroformylation of vinyl arenes. This can be achieved under solvent-free conditions. The Royal Society of Chemistry.
Noonan, Gary M.,Cobley, Christopher J.,Mahoney, Thomas,Clarke, Matthew L.
supporting information
p. 1475 - 1477
(2014/02/14)

Synthesis and Reactivity of Chiral, Wide-Bite-Angle, Hybrid Diphosphorus Ligands
Effective and modular synthetic approaches toward phosphine-phosphite ligands and phosphine-phosphonite ligands featuring a diphenyl ether backbone have been developed. The phosphine-phosphite ligands are obtained by a two-step protocol from 2-bromo-2′-methoxydiphenyl ether. The phosphine-phosphonite ligands are prepared in a four-step synthetic protocol that involves a novel, unsymmetrical diphenyl ether derived phosphine-phosphorusdiamide as key building block. Structural studies on PtII complexes with either phosphine-phosphite or phosphine-phosphonite ligands indicate strict cis coordination for these ligand systems. High-pressure NMR spectroscopy studies of Rh complexes under syngas indicate the presence of two ea isomers for Rh(H)(CO)2(PP). The existence of this mixture is further supported by high-pressure IR spectroscopy studies. In order to benchmark the activity and selectivity of these novel, wide-bite-angle, mixed-donor ligands, they were screened in Pd-catalyzed asymmetric allylic alkylation as well as Rh-catalyzed hydrogenation and hydroformylation reactions. The ligands give 100-% conversion and low-to-moderate enantioselectivity in the allylic alkylation of 1,3-diphenyl-2-propenyl acetate and cyclohexyl-2-enyl acetate with dimethyl malonate. In the hydroformylation of styrene, good conversion and regioselectivities are achieved but only moderate enantioselectivity. The ligands give good conversions in asymmetric hydrogenation of typical substrates, with good-to-excellent enantioselectivities of up to 97-% depending on the substrate. Copyright
Czauderna, Christine Fee,Cordes, David B.,Slawin, Alexandra M. Z.,Müller, Christian,Van Der Vlugt, Jarl Ivar,Vogt, Dieter,Kamer, Paul C. J.
p. 1797 - 1810
(2014/04/17)

Easily accessible and highly tunable bisphosphine ligands for asymmetric hydroformylation of terminal and internal alkenes
An efficient methodology for synthesizing a small library of easily tunable and sterically bulky ligands for asymmetric hydroformylation (AHF) has been reported. Five groups of alkene substrates have been tested with excellent conversions, moderate-to-excellent regio- and enantioselectivities. Among the best result of the reported literature, application of ligand 1 c in the highly selective AHF of the challenging substrate 2,5-dihydrofuran yielded almost one isomer in up to 99 % conversion along with enantiomeric excesses (ee) of up to 92 %. Highly enantioselective AHF of dihydropyrrole substrates is achieved using the same ligand, with up to 95 % ee and up to >1:50 β-isomer/α- isomer ratio. The simpler the better! An efficient method for the easy and tunable synthesis of a series of asymmetric hydroformylation (AHF) ligands from low-cost, commercially available starting materials has been reported. These ligands can give excellent conversions and moderate to excellent regio- and enantioselectivities for a broad range of mono- and disubstituted alkenes with a low catalyst loading (substrate-to-catalyst ratios (S/C) of 1000:1 to 3000:1).
Xu, Kun,Zheng, Xin,Wang, Zhiyong,Zhang, Xumu
p. 4357 - 4362
(2014/05/06)

Immobilized bisdiazaphospholane catalysts for asymmetric hydroformylation
Condensation reactions of enantiopure bis-3,4-diazaphospholanes (BDPs) that are functionalized with carboxylic acids enable covalent attachment to bead and silica supports. Exposure of tethered BDPs to the hydroformylation catalyst precursor, Rh(acac)(CO)2, yields catalysts for immobilized asymmetric hydroformylation (iAHF) of prochiral alkenes. Compared with homogeneous catalysts, catalysts immobilized on Tentagel resins exhibit similarly high regioselectivity and enantioselectivity. When corrected for apparent catalyst loading, the activity of the immobilized catalysts approaches that of the homogeneous analogues. Excellent recyclability with trace levels of rhodium leaching are observed in batch and flow reactor conditions. Silica-bound catalysts exhibit poorer enantioselectivities.
Adint, Tyler T.,Landis, Clark R.
p. 7943 - 7953
(2014/06/23)

Confining phosphanes derived from cyclodextrins for efficient regio- and enantioselective hydroformylation
Two confining phosphane ligands derived from either α- or β-cyclodextrin produce singly PIII-ligated metal complexes with unusual coordination spheres. High-pressure NMR studies have revealed that rhodium hydride complexes of the same type are also formed under hydroformylation conditions. This unique feature strongly favors the formation of the branched aldehyde at the expense of the linear one with high enantioselectivity in the rhodium-catalyzed hydroformylation of styrene. Rhodium in confinement: α- and β-cyclodextrin derivatives bearing introverted PIII donor atoms readily form monophosphane complexes in which the cyclodextrin cavity tightly wraps around the metal center. When used as ligands in the rhodium-catalyzed hydroformylation of styrene, they lead to both high isoselectivity and enantioselectivity.
Jouffroy, Matthieu,Gramage-Doria, Rafael,Armspach, Dominique,Semeril, David,Oberhauser, Werner,Matt, Dominique,Toupet, Loic
supporting information
p. 3937 - 3940
(2014/05/06)

Phosphinocyclodextrins as confining units for catalytic metal centres. applications to carbon-carbon bond forming reactions
The capacity of two cavity-shaped ligands, HUGPHOS-1 and HUGPHOS-2, to generate exclusively singly phosphorus-ligated complexes, in which the cyclodextrin cavity tightly wraps around the metal centre, was explored with a number of late transition metal cations. Both cyclodextrin-derived ligands were assessed in palladium-catalysed Mizoroki-Heck coupling reactions between aryl bromides and styrene on one hand, and the rhodium-catalysed asymmetric hydroformylation of styrene on the other hand. The inability of both chiral ligands to form standard bis(phosphine) complexes under catalytic conditions was established by high-pressure NMR studies and shown to have a deep impact on the two carbon-carbon bond forming reactions both in terms of activity and selectivity. For example, when used as ligands in the rhodium-catalysed hydroformylation of styrene, they lead to both high isoselectivity and high enantioselectivity. In the study dealing with the Mizoroki-Heck reactions, comparative tests were carried out with WIDEPHOS, a diphosphine analogue of HUGPHOS-2.
Jouffroy, Matthieu,Gramage-Doria, Rafael,Smeril, David,Armspach, Dominique,Matt, Dominique,Oberhauser, Werner,Toupet, Loc
p. 2388 - 2405
(2015/01/08)

1,1-P-OP ligands with P-stereogenic phosphino groups in asymmetric hydrogenations and hydroformylations
A new series of narrow-bite-angle phosphine-phosphite (1,1-P-OP) ligands (3a-d) has been efficiently prepared from the enantiopure (SP)-tert- butyl(hydroxymethyl)methylphosphino borane complex 1, a crucial intermediate. The catalytic performance of the ligands in Rh-mediated asymmetric hydrogenations and hydroformylations is described. The corresponding rhodium complexes provided excellent efficiencies (full conversion in all cases) and high enantioselectivities (up to 98% ee) for the asymmetric hydrogenation of structurally diverse functionalized alkenes. Furthermore, rhodium catalysts derived from these 1,1-P-OP ligands were highly active and gave excellent regioselectivities (branched/linear product ratios of up to 97/3) and moderate enantioselectivities in the hydroformylation of different terminal olefins.
Lao, Joan R.,Benet-Buchholz,Vidal-Ferran, Anton
p. 2960 - 2963
(2014/07/08)

Enantiopure narrow bite-angle P-OP ligands: Synthesis and catalytic performance in asymmetric hydroformylations and hydrogenations
Herein is reported the preparation of a set of narrow bite-angle P-OP ligands the backbone of which contains a stereogenic carbon atom. The synthesis was based on a Corey-Bakshi-Shibata (CBS)-catalyzed asymmetric reduction of phosphomides. The structure of the resulting 1,1-P-OP ligands, which was selectively tuned through adequate combination of the configuration of the stereogenic carbon atom, its substituent, and the phosphite fragment, proved crucial for providing a rigid environment around the metal center, as evidenced by X-ray crystallography. These new ligands enabled very good catalytic properties in the Rh-mediated enantioselective hydrogenation and hydroformylation of challenging and model substrates (up to 99 % ee). Whereas for asymmetric hydrogenation the optimal P-OP ligand depended on the substrate, for hydroformylation, a single ligand was the highest-performing one for almost all studied substrates: it contains an R-configured stereogenic carbon atom between the two phosphorus ligating groups, and an S-configured 3,3′-diphenyl-substituted biaryl unit. Ligand design: Narrow-bite-angle P-OP ligands incorporating a stereogenic carbon atom in their backbone have been synthesized by Corey-Bakshi-Shibata (CBS)-catalyzed asymmetric reduction of the corresponding intermediates followed by O-phosphorylation. Rhodium complexes of these ligands provided very good catalytic performance in hydroformylations and hydrogenations (see scheme).
Fernández-Pérez, Héctor,Benet-Buchholz, Jordi,Vidal-Ferran, Anton
p. 15375 - 15384
(2016/02/18)

Synthesis and reactivity of chiral, wide-bite-angle, hybrid diphosphorus ligands
Effective and modular synthetic approaches toward phosphine-phosphite ligands and phosphine-phosphonite ligands featuring a diphenyl ether backbone have been developed. The phosphine-phosphite ligands are obtained by a two-step protocol from 2-bromo-2′-methoxydiphenyl ether. The phosphine-phosphonite ligands are prepared in a four-step synthetic protocol that involves a novel, unsymmetrical diphenyl ether derived phosphine-phosphorusdiamide as key building block. Structural studies on PtII complexes with either phosphine-phosphite or phosphine-phosphonite ligands indicate strict cis coordination for these ligand systems. High-pressure NMR spectroscopy studies of Rh complexes under syngas indicate the presence of two ea isomers for Rh(H)(CO)2(PP). The existence of this mixture is further supported by high-pressure IR spectroscopy studies. In order to benchmark the activity and selectivity of these novel, wide-bite-angle, mixed-donor ligands, they were screened in Pd-catalyzed asymmetric allylic alkylation as well as Rh-catalyzed hydrogenation and hydroformylation reactions. The ligands give 100-% conversion and low-to-moderate enantioselectivity in the allylic alkylation of 1,3-diphenyl-2-propenyl acetate and cyclohexyl-2-enyl acetate with dimethyl malonate. In the hydroformylation of styrene, good conversion and regioselectivities are achieved but only moderate enantioselectivity. The ligands give good conversions in asymmetric hydrogenation of typical substrates, with good-to-excellent enantioselectivities of up to 97-% depending on the substrate. The design of two subclasses of chiral, mixed-donor diphosphorus ligands with a diphenylether backbone is described. Both phosphine-phosphonite and phosphine-phosphite derivatives are accessible. Coordination to PtII and RhI is described, and high-pressure spectroscopy under syngas provides information on coordination geometry. The chiral ligand systems are benchmarked in Pd-catalyzed allylic alkylation and Rh-catalyzed hydrogenation and hydroformylation.
Czauderna, Christine Fee,Cordes, David B.,Slawin, Alexandra M. Z.,Müller, Christian,Van Der Vlugt, Jarl Ivar,Vogt, Dieter,Kamer, Paul C. J.
p. 1797 - 1810
(2015/04/27)

Platinum(II) complexes incorporating racemic and optically active 1-alkyl-3-phospholene P-ligands: Synthesis, stereostructure, NMR properties and catalytic activity
Three 1-alkyl-3-phospholene 1-oxides, such as the P-ethyl, P-isobutyl and P-isopentyl derivative were prepared in racemic and enantiopure forms. After deoxygenation, the cyclic phosphines were converted to the corresponding phosphineeboranes and phosphine
Bagi, Péter,Kovács, Tamara,Szilvási, Tibor,Pongrácz, Péter,Kollár, László,Drahos, László,Fogassy, Elemér,Keglevich, Gy?rgy
p. 306 - 313
(2014/03/21)

Influence of the 4-substituents on the reversal of enantioselectivity in the asymmetric hydroformylation of 4-substituted styrenes with PtCl(SnCl 3)[(2 S, 4 S)-BDPP]
The enantioselectivity of the asymmetric hydroformylation of 4-substituted styrenes in the presence of an in situ catalyst, formed from PtCl(SnCl 3)[(2S,4S)-BDPP] and tin(II) chloride, was influenced by the reaction temperature. The preferred formation of the S and the R enantiomers of the branched aldehyde regioisomers (2a-g) was observed at low and high temperatures, respectively. The electron-donor or electron-acceptor properties of the para substituents of styrene show correlation with the changes in enantioselectivity, especially with the reversal temperature of the enantioselectivity. The reversibility of the formation of the Pt-branched alkyl intermediates, leading to the corresponding R and S enantiomers of 2-arylpropanals, depends on the Hammett constants. The electronic effect of para substituents was investigated by quantum chemical methods employing the simple olefin adducts [HPt(PH 3)2(olefin)(SnCl3)]. Excellent linear correlation was found between the para substituent constants and the electrostatic potential at nuclei of the platinum atom. Equally good correlation has been established for the other atoms as well in the coordination sphere of Pt.
Pongracz, Peter,Papp, Tamara,Kollar, Laszlo,Kegl, Tamas
supporting information
p. 1389 - 1396
(2014/04/17)

Bis(phosphite) ligands with distal regulation: Application in rhodium-mediated asymmetric hydroformylations
Small amounts of achiral polyether binders are employed to enhance the enantioselectivity of the hydroformylation of an array of diversely substituted substrates (increase of up to 62 % ee for vinyl acetate) mediated by chiral rhodium complexes derived from the α,ω-bis(phosphite)-polyether ligands 1. To the best of our knowledge, this study represents an unprecedented successful example of the positive regulation of enantioselectivity in hydroformylations.
Mon, Ignasi,Jose, D. Amilan,Vidal-Ferran, Anton
supporting information
p. 2720 - 2725
(2013/04/10)

Libraries of bisdiazaphospholanes and optimization of rhodium-catalyzed enantioselective hydroformylation
Twelve chiral bis-3,4-diazaphospholane ligands and six alkene substrates (styrene, vinyl acetate, allyloxy-tert-butyldimethylsilane, (E)-1-phenyl-1,3- butadiene, 2,3-dihydrofuran, and 2,5-dihydrofuran) probe the influence of steric bulk on the activity and selectivity of asymmetric hydroformylation (AHF) catalysts. Reaction of an enantiopure bisdiazaphospholane tetraacyl fluoride with primary or secondary amines yields a small library of tetracarboxamides. For all six substrates, manipulation of reaction conditions and bisdiazaphospholane ligands enables state-of-the-art performance (90% or higher ee, good regioselectivity, and high turnover rates). For the nondihydrofuran substrates, the previously reported ligand, (S,S)-2, is generally most effective. However, optimal regio- and enantioselective hydroformylation of 2,3-dihydrofuran (up to 3.8:1 α-isomer/β-isomer ratio and 90% ee for the α-isomer) and 2,5-dihydrofuran (up to 1:30 α-isomer/β- isomer ratio and 95% ee for the β-isomer) arises from bisdiazaphospholanes containing tertiary carboxamides. Hydroformylation of either 2,3- or 2,5-dihydrofuran yields some of the β-formyl product. However, the absolute sense of stereochemistry is inverted. A stereoelectronic map rationalizes the opposing enantiopreferences
Adint, Tyler T.,Wong, Gene W.,Landis, Clark R.
p. 4231 - 4238
(2013/06/05)

Small bite-angle P-OP ligands for asymmetric hydroformylation and hydrogenation
A series of small bite-angle phosphine-phosphite (P-OP) ligands have been synthesized by a two-step method. The key intermediate was prepared by an unprecedented asymmetric carbonyl reduction of a phosphamide using the CBS (Corey-Bakshi-Shibata) catalyst. The topology of these ligands (a configurationally stable stereogenic carbon with two heteroatom substituents) and their small bite-angle (created by the close proximity of the two ligating groups to the metal center) together provide a rigid asymmetric environment around this center, enabling high stereoselectivity in hydroformylations and hydrogenations of standard substrates.
Fernandez-Perez, Hector,Benet-Buchholz,Vidal-Ferran, Anton
supporting information
p. 3634 - 3637
(2013/08/23)