- Microwave-assisted cleavage of cysteine perfluoroaryl thioethers
-
The cysteine- perfluoroarene SNAr reaction allows for the sequence-specific attachment of dyes and affinity tags to peptides and proteins. However, while many methods exist for the desulfuration of native and functionalized cysteine residues, there are no reports of their application to perfluoroarylated cysteines. Herein we report both the hydrogenolysis of a perfluoroarylated cysteine to alanine and elimination to dehydroalanine, reactions that are both accelerated by microwave irradiation.
- Bednar, Taylor N.,Resnikoff, Alissa R.,Gavenonis, Jason
-
-
Read Online
- Mechanistically Guided One Pot Synthesis of Phosphine-Phosphite and Its Implication in Asymmetric Hydrogenation
-
Although hybrid bidentate ligands are known to yield highly enantioselective products in asymmetric hydrogenation (AH), synthesis of these ligands is an arduous process. Herein, a one pot, atom-economic synthesis of a hybrid phosphine-phosphite (L1) is reported. After understanding the reactivity difference between an O-nucleophile versus C-nucleophile, one pot synthesis of Senphos (L1) was achieved (72 %). When L1 was treated with [Rh], 31P NMR revealed bidentate coordination to Rh. Senphos, in the presence of rhodium, catalyzes the AH of Methyl-2-acetamido-3-phenylacrylate and discloses an unprecedented turn over frequency of 2289, along with excellent enantio-selectivity (92 %). The generality is demonstrated by hydrogenating an array of alkenes. The AH operates under mild conditions of 1–2 bar H2 pressure, at room temperature. The practical relevance of L1 is demonstrated by scaling-up the reaction to 1 g and by synthesizing DOPA, a drug widely employed for the treatment of Parkinson's disease. Computational insights indicate that the R isomer is preferred by 3.8 kcal/mol over the S isomer.
- Sen, Anirban,Kumar, Rohit,Pandey, Swechchha,Vipin Raj,Kumar, Pawan,Vanka, Kumar,Chikkali, Samir H.
-
supporting information
(2022/01/11)
-
- 2-(1S)-Camphanoyloxy-2′-phosphanylbiphenyl Ligands – Synthesis, Structure, and Preliminary Tests in Transition-Metal Catalysis
-
Diastereoisomer separation of the (1S)-camphanic acid 2-isopropylphenylphosphanyl-phenyl ester 1 exemplifies the potential of (1S)-camphanoyl chloride for enantiomer separation of hydroxyl-functional asymmetric phosphanes. Esterification of lithium 2′-phosphanylbiphenyl-2-olates, generated from the respective 2-OH or 2-OSiMe3 precursors 2aOH and 2b–fSi, furnished the 2-(1S)-camphanoyloxy-biphenylphosphanes 3a–c as 1:1 mixtures of diastereomers with low barriers for interconversion by rotation around the C–C axis (ΔG# = 70–73 kJ mol–1 for 3a and 3c by 31P VT NMR spectroscopy). The P-asymmetric compounds 3d–f form 1:1 mixtures of stereoisomers. There is a tendency to cocrystallization of two preferred diastereoisomers, as shown by the crystal structure analyses of 3dD and 3fD, and in solution, there is a tendency toward partial isomerization to the sterically less-favored atropisomers. The [RhCl(cod)(3dD)] complex 4dD, however, seems stable in solution. Excess 2dLi reacted with (1S)-camphanoyl chloride preferentially to form the (SP,Rax,1S) isomer, which was separated by crystallization as enantiopure 3dE, characterized by single-crystal XRD. Preliminary screening tests of this ligand in Rh-catalyzed asymmetric hydrogenations of N-(1-phenylvinyl)acetamide allowed high conversion and up to 59 % ee. Hydrosilylation of acetophenone proceeded with 78 % conversion and 48 % ee; Suzuki–Miyaura couplings of 1-bromo-2-naphthol with PhB(OH)2, in the presence of 3b/[Pd(OAc)2], gave yields up to 98 %.
- Wawrzyniak, Piotr,Kindermann, Markus K.,Thede, Gabriele,Thede, Richard,Jones, Peter G.,Enthaler, Stephan,Junge, Kathrin,Beller, Matthias,Heinicke, Joachim W.
-
supporting information
p. 2762 - 2773
(2017/06/06)
-
- Dual-pathway chain-end modification of RAFT polymers using visible light and metal-free conditions
-
We report a metal-free strategy for the chain-end modification of RAFT polymers utilizing visible light. By turning the light source on or off, the reaction pathway in one pot can be switched between either complete desulfurization (hydrogen chain-end) or simple cleavage (thiol chain-end), respectively. The versatility of this process is exemplified by application to a wide range of polymer backbones under mild, quantitative conditions using commercial reagents.
- Discekici, Emre H.,Shankel, Shelby L.,Anastasaki, Athina,Oschmann, Bernd,Lee, In-Hwan,Niu, Jia,McGrath, Alaina J.,Clark, Paul G.,Laitar, David S.,De Alaniz, Javier Read,Hawker, Craig J.,Lunn, David J.
-
supporting information
p. 1888 - 1891
(2017/02/10)
-
- Assisted Tandem Catalysis: Metathesis Followed by Asymmetric Hydrogenation from a Single Ruthenium Source
-
Here we report the first example of a tandem metathesis-asymmetric hydrogenation protocol where the prochiral olefin generated by metathesis is hydrogenated with high enantioselectivity by an in situ formed chiral ruthenium catalyst. We show that either the ruthenium metathesis catalysts or the ruthenium species formed during the metathesis reaction can be converted into an efficient asymmetric hydrogenation catalyst upon addition of a chiral ligand and an alcohol. The performance in asymmetric hydrogenation appears to be very dependent on the solvent, the chiral ligand, and the prochiral substrate.
- Renom-Carrasco, Marc,Gajewski, Piotr,Pignataro, Luca,Devries, Johannes G.,Piarulli, Umberto,Gennari, Cesare,Lefort, Laurent
-
supporting information
p. 2223 - 2228
(2015/07/27)
-
- P-CHIROGENIC ORGANOPHOSPHORUS COMPOUNDS
-
The present invention relates to novel P-chirogenic organophosphorus compounds of general formula (I). The present invention also provides a process for the synthesis of said compounds of formula (I). The present invention also relates to intermediate products of general formulae (II), (III) and (IV), as shown below, which are involved in the synthesis of compounds (I). Further, the invention relates to metal complexes comprising compounds (I) as ligands. The novel compounds and complexes of the present invention are useful in asymmetric catalysis by transition metal complexes or organocatalysis, especially for asymmetric hydrogenation or allylation. Compounds of general formula (I) may useful as agrochemical and therapeutic substances, or as reagents or intermediates for fine chemistry.
- -
-
Page/Page column 88; 89; 90
(2013/03/26)
-
- Highly enantioselective Rh-catalyzed hydrogenations with heterocombinations of pentafluorobenzyl- and methoxybenzyl-derived binaphthyl phosphites
-
The Rh-catalyzed hydrogenations of dimethyl itaconate and methyl acetamido acrylate using selected heterocombinations of pentafluorobenzyl- and methoxybenzyl-derived binaphthyl phosphites proved to be highly enantioselective (ee 93-99%). In these selected
- Lynikaite, Benita,Cvengro?, Ján,Piarulli, Umberto,Gennari, Cesare
-
p. 755 - 759
(2008/03/30)
-
- DIPHOSPHINES AND METAL COMPLEXES
-
Compounds of the formulae (I) and (II), or a mixture of these enantiomers, where R'1 is C1-C4-alkyl and n is 0, 1 or 2; R1 is C1-C8-alkyl, C2-C8-alken-1-yl, -CH2-OR or - CH2-NR5R6; the two radicals R2 are identical or different and are each hydrogen or a monovalent radical of an electrophilic organic compound, or one R2 has this meaning and the other R2 is hydrogen; sec-phos is a secondary phosphino group; R is C1-C8- alkyl and R5 and R6 are each C1-C6-alkyl or R5 and R6 together form tetramethylene, pentamethylene or 3-oxa-1,5-pentylene, are ligands for metal complexes which can be used as valuable homogeneous catalysts for asymmetric syntheses. The compounds are obtained by a novel process in which 3,3'-metallated 1,1'-di-R1-2,2'- dibromoferrocenes are firstly reacted with sec-phos halide, the bromine atoms are then replaced by lithium and the substituent R2 is subsequently introduced by reaction with an electrophilic organic compound or with water.
- -
-
Page/Page column 41; 43
(2008/06/13)
-
- UREAphos: Supramolecular bidentate ligands for asymmetric hydrogenation
-
Supramolecular bidentate phosphite ligands are presented as a new class of ligands for rhodium catalysed asymmetric hydrogenation. The Royal Society of Chemistry.
- Sandee, Albertus J.,Van Der Burg, Alida M.,Reek, Joost N. H.
-
p. 864 - 866
(2007/10/03)
-
- Directed evolution of enantioselective hybrid catalysts: a novel concept in asymmetric catalysis
-
The concept of directed evolution of enantioselective hybrid catalysts was proposed in 2001/2002 and implemented experimentally for the first time in a proof-of-concept study in 2006. The idea is based on directed evolution, which comprises repeating cycl
- Reetz, Manfred T.,Rentzsch, Martin,Pletsch, Andreas,Maywald, Matthias,Maiwald, Peter,Peyralans, Jér?me J.-P.,Maichele, Andrea,Fu, Yu,Jiao, Ning,Hollmann, Frank,Mondière, Régis,Taglieber, Andreas
-
p. 6404 - 6414
(2008/02/04)
-
- Inverted supercritical carbon dioxide/aqueous biphasic media for rhodium-catalyzed hydrogenation reactions
-
An inverted supercritical carbon dioxide (scCO2)/aqueous biphasic system has been used as reaction media for Rh-catalysed hydrogenation of polar substrates. Chiral and achiral CO2-philic catalysts were efficiently immobilised in scCO2 as the stationary phase, while the polar substrates and products were contained in water as the mobile phase. Notably, product separation and catalyst recycling were conducted without depressurisation of the autoclave, The catalyst phase was reused several times with high conversion and product recovery of more than 85%. Loss of rhodium and phosphorus by leaching were found to be below the detection limit after the first two cycles in the majority of repetitive experiments. The reaction conditions were optimised with a minimum of experiments by using a simplex algorithm in a sequential optimisation. Total turnover numbers (TTNs) of up to 1600, turnover frequencies (TOFs) of up to 340 h-1 and ee's up to 99% were obtained in repetitive batch operations. The scope of the devised catalytic system has been investigated and a semicontinuous reaction setup has been implemented. The chiral ligand (R,S)-3-H2F6-BINAPHOS allowed highly enantioselective hydrogenation of itaconic acid and methyl-2-acetamidoacrylate combined with a considerable catalyst stability in these reaction media.
- Burgemeister, Katja,Francio, Giancarlo,Gego, Volker H.,Greiner, Lasse,Hugl, Herbert,Leitner, Walter
-
p. 2798 - 2804
(2008/02/04)
-
- Repetitive application of a fluorous chiral BINAP-Ru complex in the asymmetric hydrogenation of olefins
-
A trisperfluoroalkylsilyl-modified (S)-BINAP ligand has been prepared and its pertinent Ru complex applied to the asymmetric hydrogenation of olefins. Efficient separation of the Ru catalyst by filtration and its reuse was achieved. Relative to the untagg
- Horn, Joachim,Bannwarth, Willi
-
p. 2058 - 2063
(2008/02/04)
-
- Chiral ionic phosphites and diamidophosphites: A novel group of efficient ligands for asymmetric catalysis
-
Seven members of a new class of chiral P-monodentate cationic phosphites and diamidophosphites have been synthesized for the first time and tested as ligands in asymmetric transition metal catalysis. Up to 96% ee was achieved in the rhodium-catalyzed asym
- Gavrilov, Konstantin N.,Lyubimov, Sergey E.,Bondarev, Oleg G.,Maksimova, Marina G.,Zheglov, Sergey V.,Petrovskii, Pavel V.,Davankov, Vadim A.,Reetz, Manfred T.
-
p. 609 - 616
(2008/02/09)
-
- Enantioselective hydrogenation with self-assembling rhodium phosphene catalysts: Influence of ligand structure and solvent
-
Three sets of new and related chiral phospholane and phosphepine ligands have been prepared for Rh-catalyzed enantioselective hydrogenation. The size and substitution pattern of the cyclic monophosphanes were varied. More importantly, the ligands differ in the nature of the heterocyclic group linked to the trivalent phosphorus atom: 2-pyridone or 2-alkoxypyridine. In the corresponding Rh complexes, the pyridone units of two monodentate P ligands can assemble by hydrogen bonding and form chelates. In contrast, synthetic precursors bearing alkoxypyridine appendages are not able to aggregate via intramolecular hydrogen bonds. The nature of self-assembly is dependent on the nature of the P ligand and the solvent used for the hydrogenation (CH 2Cl2 vs. MeOH). These features affect the rate of the reaction as well as the enantioselectivity, which varied in the range of 0-99 % ee Complexation studies and DFT calculations were performed to explain these differences.
- Birkholz, Mandy-Nicole,Dubrovina, Natalia V.,Jiao, Haijun,Michalik, Dirk,Holz, Jens,Paciello, Rocco,Breit, Bernhard,Boerner, Armin
-
p. 5896 - 5907
(2008/02/13)
-
- INDOLPhos: novel hybrid phosphine-phosphoramidite ligands for asymmetric hydrogenation and hydroformylation
-
Hybrid bidentate phosphine-phosphoramidite ligands are prepared in a modular 2-step sequence and their rhodium complexes display high selectivity in rhodium catalysed hydrogenation and hydroformylation reactions. The Royal Society of Chemistry.
- Wassenaar, Jeroen,Reek, Joost N. H.
-
p. 3750 - 3753
(2008/03/13)
-
- Chiral calix[4]arene-based diphosphites as ligands in the asymmetric hydrogenation of prochiral olefins
-
Chiral calixarene-based diphosphite ligands 3a-d have been obtained via lower-rim functionalisation of the p-tert-butylcalix[4]arene core. High enantiomeric excesses (up to 94%) and good activities were obtained in the rhodium-catalyzed asymmetric hydroge
- Marson, Angelica,Freixa, Zoraida,Kamer, Paul C. J.,Van Leeuwen, Piet W. N. M.
-
p. 4587 - 4591
(2008/03/18)
-
- Enantioselective catalysis with tropos ligands in chiral ionic liquids
-
Enantioselective homogeneous rhodium-catalysed hydrogenation using tropoisomeric biphenylphosphine ligands was accomplished in readily available chiral ionic liquids and the catalytic system could be reused after extraction with scCO2. The Royal Society of Chemistry.
- Schmitkamp, Mike,Chen, Dianjun,Leitner, Walter,Klankermayer, Juergen,Francio, Giancarlo
-
p. 4012 - 4014
(2008/03/27)
-
- Chiral bisphospholane ligands (Me-ketalphos): Synthesis of their Rh(I) complexes and applications in asymmetric hydrogenation
-
Rhodium complexes of functionalized bisphospholane ligands (S,S,S,S-Me-ketalphos) 1 and (R,S,S,R-Me-ketalphos) 2 have been used as catalyst precursors for the asymmetric hydrogenation of several different types of functionalized olefins and have achieved
- Dai, Qian,Wang, Chun-Jiang,Zhang, Xumu
-
p. 868 - 871
(2007/10/03)
-
- Synthesis of a novel spiro bisphosphinite ligand and its application in Rh-catalyzed asymmetric hydrogenation
-
A novel, chiral bisphosphinite ligand (R)-SpiroBIP has been synthesized. The rhodium complex of the ligand was found to be highly enantioselective in the asymmetric hydrogenation of α-dehydroamino acid derivatives.
- Guo, Zhenqiu,Guan, Xiaoyu,Chen, Zhiyong
-
p. 468 - 473
(2007/10/03)
-
- Chiral diphosphites and diphosphoramidites as cheap and efficient ligands in Rh-catalyzed asymmetric olefin hydrogenation
-
Chiral diphosphites and diphosphoramidites derived from BINOL or diphenylprolinol are efficient ligands in asymmetric Rh-catalyzed olefin hydrogenation, provided the proper achiral backbone is chosen. The Royal Society of Chemistry 2006.
- Reetz, Manfred T.,Mehler, Gerlinde,Bondarev, Oleg
-
p. 2292 - 2294
(2007/10/03)
-
- New chiral monodentate phospholane ligands by highly stereoselective hydrophosphination
-
New chiral phospholanes 6 were prepared in both enantiomeric forms starting from l- and d-tartaric acid. The key step in the synthetic sequence is the double hydrophosphination of unsaturated chiral bis(lactone) 9 by NaPhPH(BH3). This method wa
- Bilenko, Vitaliy,Spannenberg, Anke,Baumann, Wolfgang,Komarov, Igor,Boerner, Armin
-
p. 2082 - 2087
(2007/10/03)
-
- Nonlinear effects in Rh-catalyzed asymmetric olefin hydrogenation using mixtures of chiral monodentate P ligands
-
(Chemical Equation Presented) Well mixed: A 1:1 mixture of two different binaphthol-derived monophosphonite ligands (L) is employed in the Rh-catalyzed hydrogenation of prochiral olefins (see scheme; cod = cyclooctadiene). Variation of the enantiopurity o
- Reetz, Manfred T.,Fu, Yu,Meiswinkel, Andreas
-
p. 1412 - 1415
(2007/10/03)
-
- Directed evolution of hybrid enzymes: Evolving enantioselectivity of an achiral Rh-complex anchored to a protein
-
The concept of utilizing the methods of directed evolution for tuning the enantioselectivity of synthetic achiral metal-ligand centers anchored to proteins has been implemented experimentally for the first time. The Royal Society of Chemistry 2006.
- Reetz, Manfred T.,Peyralans, Jerome J.-P.,Maichele, Andrea,Fu, Yu,Maywald, Matthias
-
p. 4318 - 4320
(2007/10/03)
-
- New modular P-chiral ligands for Rh-catalyzed asymmetric hydrogenation
-
New modular P-chiral ligands have been prepared from commercially available (S)-α,α-diphenylprolinol. With these new types of ligands, up to 95% ee was achieved in the Rh-catalyzed asymmetric hydrogenation of functionalized olefins.
- Bondarev, Oleg G.,Goddard, Richard
-
p. 9013 - 9015
(2007/10/03)
-
- Engineering a polymeric chiral catalyst by using hydrogen bonding and coordination interactions
-
(Chemical Equation Presented) Noncovalent interactions are used to generate a polymeric supramolecular chiral catalyst (see picture). This heterogeneous catalyst, which is based on Feringa's MonoPhos/RhI system, is formed by orthogonal self-ass
- Shi, Lei,Wang, Xingwang,Sandoval, Christian A.,Li, Mingxing,Qi, Qiaoyan,Li, Zhanting,Ding, Kuiling
-
p. 4108 - 4112
(2007/10/03)
-
- Chiral phosphabarrelene ligands: Synthesis and evaluation in rhodium-catalyzed asymmetric hydrogenation
-
The first chiral and enantiomerically pure monodentate and bidentate phosphabarrelene ligands have been prepared and their potential in rhodium-catalyzed asymmetric hydrogenation has been evaluated. Georg Thieme Verlag Stuttgart.
- Breit, Bernhard,Fuchs, Evelyn
-
p. 2121 - 2128
(2008/02/03)
-
- Chiral diphosphinoditerpenes and their transition metals complexes
-
Chiral diphosphinoterpene compounds (I) are new. Chiral diphosphinoterpene compounds of formula (I) are new. *2, *3 : stereogenically marked carbon in R- or S- configuration where the substitutents are arranged in cis form related to the connecting carbon
- -
-
Page/Page column 18
(2008/06/13)
-
- Avoiding the classical resolution during the synthesis of MeO-BIPHEP and 3,3′-disubstituted derivatives
-
The Ullmann coupling of 1 (R = H) gives a 2:1 mixture of diastereomers 2 (R = H) in 81% yield that are easily separated by silica gel chromatography. This procedure avoids the generally cumbersome and sometimes difficult resolution step with DBTA. Similar Ullmann couplings and separation of the corresponding diastereomers are employed with other derivatives of 1 (R = OtBu, iPr, Ph, and mesityl) ultimately affording a new series of 3,3′-disubsituted-MeO-BIPHEP derivatives. The use of these new derivatives in palladium-catalyzed asymmetric Heck reaction, Pd-catalyzed polyene cyclizations and rhodium-catalyzed hydrogenations is also reported.
- Gorobets, Evgueni,Wheatley, Bronwen M. M.,Hopkins, J. Matthew,McDonald, Robert,Keay, Brian A.
-
p. 3843 - 3846
(2007/10/03)
-
- The role of additional solvents in transition metal complex catalyzed asymmetric reductions in ionic liquid containing systems
-
When ionic liquids (ILs) are employed as solvents for transition metal complex (TMC) catalyzed reductions, a second solvent can be added to increase the efficiency of the catalytic cycle and the solubility of the reactant in the IL phase. Two industrially relevant asymmetric hydrogenations, the enantioselective reductions of methyl 2-acetamidoacrylate with Rh-EtDuPHOS and methyl acetoacetate with Ru-BINAP, were performed in different catalytic systems including 1-butyl-3-methylimidazolium hexafluorophosphate/ tetrafluoroborate as ILs. Product separation and TMC recycling was performed by extracting the product from the reaction mixture. This can be accomplished by cooling the system, by adding an excess of the second solvent or by adding a third solvent. A high solubility of the second solvent in the IL catalytic phase favors the reaction activity, but can induce leaching of the IL and TMC.
- Wolfson, Adi,Vankelecom, Ivo F.J.,Jacobs, Pierre A.
-
p. 3558 - 3566
(2007/10/03)
-
- Asymmetric hydrogenation of prochiral olefins catalysed by furanoside thioether-phosphinite Rh(I) and Ir(I) complexes
-
Thioether-phosphinite ligands (P-SR, R = Ph, Pri and Me) bearing substituents with different steric demands on the sulfur centre were tested in the rhodium- and iridium-catalysed asymmetric hydrogenation of prochiral olefins. High enantiomeric excesses (up to 96%) and good activities (TOF up to 860 mol product × (mol catalyst precursor × h)-1) were obtained for α-acylaminoacrylates derivatives. Our results show that enantiomeric excesses depended strongly on the steric properties of the substituent in the thioether moiety, the metal source and the substrate structure. A bulky group in the thioether moiety along with the metal Rh had a positive effect on enantioselectivity. Reaction of these chiral ligands with [M(cod)2]BF4 (M = Ir, Rh; cod = 1,5-cyclooctadiene) yielded complexes [M(cod)(P-SR)]BF4, which were present in only one diastereomeric form having the sulfur substituent in a pseudoaxial disposition. The addition of H2 to iridium complexes gave the cis- dihydridoiridium(III) complexes [IrH2(cod)(P-SR)]BF4. For complexes [IrH2(cod)(P-SPh)]BF4 and [IrH 2(cod)(P-SMe)] only one isomer was present in solution. However, for the complex [IrH2(cod)(P-Si-Pr)]BF4, which contained the more hindered substituent on sulfur, two isomers were detected. In all cases there was a pseudoaxial disposition of the sulfur substituents. The Royal Society of Chemistry 2005.
- Guimet, Eugeni,Dieguez, Montserrat,Ruiz, Aurora,Claver, Carmen
-
p. 2557 - 2562
(2007/10/03)
-
- Asymmetric hydrogenation of enamides with a new chiral phosphine- phosphinite ligand
-
A new mixed chiral phosphine-phosphinite 4 obtained from enantiomerically pure (S)-(+)-3-boronatodiphenyl-phosphanyl butanoic acid 1 was synthesized in four steps. This new chiral ligand was used in the asymmetric hydrogenation of dehydroamino acids with
- Boyer, Nicolas,Leautey, Matthieu,Jubault, Philippe,Pannecoucke, Xavier,Quirion, Jean-Charles
-
p. 2455 - 2458
(2007/10/03)
-
- Ferrocenyl bis-phosphine ligands bearing sulfinyl, sulfonyl or sulfenyl groups: Applications in asymmetric hydrogenation and allylic alkylation reactions
-
A new series of chiral ferrocenyl bis-phosphine ligands have been synthesized. Elements of planar and central chirality have been incorporated into a ferrocene backbone through sulfinyl, sulfonyl and sulfenyl groups at the ortho-position to the phosphines
- Raghunath, Malati,Gao, Wenzhong,Zhang, Xumu
-
p. 3676 - 3681
(2007/10/03)
-
- Chiral rodlike platinum complexes, double helical chains, and potential asymmetric hydrogenation ligand based on "linear" building blocks: 1,8,9,16-Tetrahydroxytetraphenylene and 1,8,9,16-tetrakis(diphenylphosphino) tetraphenylene
-
This paper is concerned with the synthesis of 1,8,9,16- tetrahydroxytetraphenylene (3a) via copper-(II)-mediated oxidative coupling, its resolution to optical antipodes, and its conversion to 1,8,9,16- tetrakis(diphenylphosphino)tetraphenylene (3b). On th
- Peng, Hai-Yan,Lam, Chi-Keung,Mak, Thomas C. W.,Cai, Zongwei,Ma, Wai-Tang,Li, Yu-Xue,Wong, Henry N. C.
-
p. 9603 - 9611
(2007/10/03)
-
- Rh-catalyzed asymmetric hydrogenation of prochiral olefins with a dynamic library of chiral TROPOS phosphorus ligands
-
A library of 19 chiral tropos phosphorus ligands, based on a flexible (tropos) biphenol unit and a chiral P-bound alcohol (11 phosphites) or secondary amine (8 phosphoramidites), was synthesized. These ligands were screened, individually and as a combination of two, in the rhodium-catalyzed asymmetric hydrogenation of dehydro-α-amino acids, dehydro-β-amino acids, enamides and dimethyl itaconate. ee values up to 98% were obtained for the dehydro-α-amino acids, by using the best combination of ligands, a phosphite [4-P(O)2O] and a phosphora midite [13-P(O)2N]. Kinetic studies of the reactions with the single ligands and with the combination of phosphite [4-P(O)2O] and phosphoramidite [13-P(O) 2N] have shown that the phosphite, despite being less enantioselective, promotes the hydrogenation of methyl 2-acetamidoacrylate and methyl 2-acetamidocinnamate faster than the mixture of the same phosphite with the phosphoramidite, while the phosphoramidite alone is much less active. In this way, the reaction was optimized by lowering the phosphite/phosphoramidite ratio (the best ratio is 0.25 equiv phosphite/1.75 equiv phosphoramidite) with a resulting improvement of the product enantiomeric excess. A simple mathematical model for a better understanding of the variation of the enantiomeric excess with the phosphite/ phosphoramidite ratio is also presented.
- Monti, Chiara,Gennari, Cesare,Piarulli, Umberto,De Vries, Johannes G.,De Vries, Andre H. M.,Lefort, Laurent
-
p. 6701 - 6717
(2007/10/03)
-
- Asymmetric hydrogenation using chiral Rh complexes immobilised with a new ion-exchange strategy
-
Rh diphosphine complexes using DuPhos and JosiPhos as chiral ligands have been immobilised by ion exchange into the mesoporous material MCM-4]. When used as catalysts for the enantioselective hydrogenation of dimethyl itaconate and methyl-2-acetamidoacrylate. these heterogeneous catalysts give catalytic performance in terms of yield and enantioselection that arc comparable to the corresponding homogeneous catalysts. Furthermore, the heterogeneous catalysts can be readily recovered and reused without loss of catalyst performance. A second immobilisation strategy is described in which [Rh(COD)2] +BF44- is initially immobilised by ion exchange and subsequently modified by the chiral diphosphine and this give comparable catalyst performance. This immobilisation strategy opens up the possibility of easy ligand-screening for parallel synthesis and libraries. The Royal Society of Chemistry 2005.
- Hems, William P.,McMorn, Paul,Riddel, Stewart,Watson, Simon,Hancock, Frederich E.,Hutchings, Graham J.
-
p. 1547 - 1550
(2007/10/03)
-
- ASYMMETRIC SYNTHESIS CATALYZED BY TRANSITION METAL COMPLEXES WITH CYCLIC CHIRAL PHOSPHINE LIGANDS
-
The present invention relates to rigid chiral ligands usefull in making catalysts for asymmetric synthesis. More particularly, the present invention relates to new monodentate and bidentate cyclic chiral phosphine ligands which are formed into catalysts to provide high selectivity of the enantiomeric structure of the end-product.
- -
-
-
- Catechol-based phosphoramidites: A new class of chiral ligands for rhodium-catalyzed asymmetric hydrogenations
-
The synthesis and application of a new class of catechol-based phosphoramidites is described. Ees up to 99% were obtained in the rhodium-catalyzed asymmetric hydrogenation of dehydroamino acids and enamides.
- Hoen, Rob,Van Den Berg, Michel,Bernsmann, Heiko,Minnaard, Adriaan J.,De Vries, Johannes G.,Feringa, Ben L.
-
p. 1433 - 1436
(2007/10/03)
-
- Application of P-chirogenic bisphospholane ligands to rhodium catalyzed asymmetric hydrogenation of α- and β-acetamido dehydroamino acid derivatives
-
Two previously reported P-chirogenic bisphospholane rhodium catalysts have been applied to the asymmetric hydrogenation of α- and β-acetamido dehydroamino acid derivatives. For α-acetamido dehydroamino acid derivatives, catalyst 4 produced very high enantiomeric excesses. These are contrasted with the previously reported enantiomeric excesses using catalyst 2. Both catalysts provide excellent enantioselectivity (96%) for the β-acetamido dehydroamino acid derivative, (E)-methyl 3-acetamido-2- butenoate. However, catalyst 2 produces higher enantioselectivity (89%) for the (Z)-isomer when compared to catalyst 4 (83%).
- Hoge, Garrett,Samas, Brian
-
p. 2155 - 2157
(2007/10/03)
-
- The synthesis of new chiral phosphine-phosphinites, phosphine- phosphoramidite, and phosphine-phosphite ligands and their applications in asymmetric hydrogenation
-
New chiral phosphine-phosphinite, phosphine-phosphoramidite ligands and phosphine-phosphite 1a, 1b, 2 and 3 have been synthesized and examined in the enantioselective hydrogenation of dehydroamino acid derivatives and α-aryl enamides. The results demonstr
- Jia, Xian,Li, Xingshu,Lam, Wing Sze,Kok, Stanton H.L.,Xu, Lijin,Lu, Gui,Yeung, Chi-Hung,Chan, Albert S.C.
-
p. 2273 - 2278
(2007/10/03)
-
- Carbohydrate-derived monophosphite ligands for Rh-catalyzed enantioselective hydrogenation of α- and β-dehydroamino acid esters
-
A series of monophosphite ligands derived from D-fructose and D-glucose have been synthesized and employed in Rh-catalyzed asymmetric hydrogenation of α- and β-dehydroamino acid esters. A variety of chiral α- and β-amino acid esters have been obtained in
- Huang, Hanmin,Liu, Xiongcai,Chen, Song,Chen, Huilin,Zheng, Zhuo
-
p. 2011 - 2019
(2007/10/03)
-
- Self-supported heterogeneous catalysts for enantioselective hydrogenation
-
"Self-supported" catalysts were prepared by the reaction of bis-MonoPhos ligand with rhodium(I) metallic ion on the basis of molecular assembling through coordination. These polymeric metal-organic assemblies are insoluble in common organic solvents and,
- Wang, Xingwang,Ding, Kuiling
-
p. 10524 - 10525
(2007/10/03)
-
- Furanoside diphosphinites as suitable ligands for the asymmetric catalytic hydrogenation of prochiral olefins
-
Diphosphinite ligands, derived from inexpensive D-(+)-xylose, were tested in the rhodium- and iridium-catalyzed asymmetric hydrogenation of prochiral olefins. Our results show that the enantiomeric excesses are strongly dependent on the absolute configura
- Guimet, Eugeni,Dieguez, Montserrat,Ruiz, Aurora,Claver, Carmen
-
p. 2247 - 2251
(2007/10/03)
-
- Novel chiral diphosphine ligands with a pinene core obtained via an allylphosphinite-allylphosphine oxide rearrangement
-
A number of new chiral diphosphine ligands with a pinene framework were synthesized and tested in some transition metal-catalyzed asymmetric reactions (enantioselectivities up to 84% ee were achieved). The [2,3]-sigmatropic allylphosphinite-allyl phosphin
- Gavryushin, Andrei,Polborn, Kurt,Knochel, Paul
-
p. 2279 - 2288
(2007/10/03)
-
- Versatile synthesis of chiral aminophosphine phosphinites (AMPPs) as ligands for enantioselective hydrogenation
-
New chiral aminophosphine phosphinite (AMPP) ligands with different P-aryl substituents were prepared from (1R,3S,4S)-2-azabicyclo[2.2.1]hept-3-ylmethanol by a new and chemoselective synthetic approach. The ligands showed good enantioselectivity (up to 91
- Dubrovina, Natalia V.,Tararov, Vitali I.,Kadyrova, Zenfira,Monsees, Axel,Boerner, Armin
-
p. 2047 - 2051
(2007/10/03)
-
- C2-symmetric diphosphinite ligands derived from carbohydrates. The strong influence of remote stereocenters on asymmetric rhodium-catalyzed hydrogenation.
-
Modular ligands of C(2) symmetry (13a-e, 14a,b,d, and ent-9), systematically modified at positions 2 and 5, were easily prepared from d-glucosamine, D-glucitol, and tartaric acid, respectively. The application of these ligands in the rhodium-catalyzed hyd
- Aghmiz, Mohamed,Aghmiz, Ali,Diaz, Yolanda,Masdeu-Bulto, Anna,Claver, Carmen,Castillon, Sergio
-
p. 7502 - 7510
(2007/10/03)
-
- Synthesis of chiral monodentate binaphthophosphepine ligands and their application in asymmetric hydrogenations
-
A general synthesis of chiral monodentate 4,5-dihydro-3H- dinaphthophosphepines 4 and a detailed study of the catalytic performance of the resulting ligands 4a-n in benchmark hydrogenation reactions is presented. Hydrogenation of methyl α-acetamidocinnamate 11 and methyl α-acetamidoacrylate 13 proceeded with enantioselectivities up to 95% and 94%, respectively. The best enantioselectivity for the rhodium-catalyzed hydrogenation of dimethyl itaconate 15 was 88%.
- Junge, Kathrin,Hagemann, Bernhard,Enthaler, Stephan,Spannenberg, Anke,Michalik, Manfred,Oehme, Guenther,Monsees, Axel,Riermeier, Thomas,Beller, Matthias
-
p. 2621 - 2631
(2007/10/03)
-
- Noncovalent anchoring of asymmetric hydrogenation catalysts on a new mesoporous aluminosilicate: Application and solvent effects
-
A new Bronsted acidic aluminosilicate, AlTUD-1, with ideal characteristics for catalyst immobilisation (mesoporous structure, high surface area, and high Altetrahedral/Si ratio), was used successfully for the noncovalent anchoring of two well-established asymmetric hydrogenation catalysts: [RhI(cod){(R,R)-MeDuPHOS}]BF4 (1) and [Rh I(cod){(S,S)-DiPAMP}]BF4 (2). The new heterogeneous catalysts, 1-AlTUD-1 and 2-AlTUD-1, prepared by a straightforward ion-exchange procedure, were highly active and selective in the asymmetric reduction of dimethyl itaconate (3) and methyl 2-acetamidoacrylate (4), giving enantiomeric excesses of up to >98%. The catalysts showed similar behaviour to their homogeneous counterparts. Catalyst 2-AlTUD-1 could be re-used multiple times without loss of enantioselectivity or activity. Leaching of Rh showed a significant dependence on the polarity of the solvent in which the catalysis was performed. By applying tert-butylmethyl ether (MTBE) as solvent, the loss of Rh could be reduced to 0.1%. The solvent also had a noteworthy effect on the enantioselectivity in the hydrogenation of 4 (an effect not seen with 3 as substrate), that is, in MeOH the ee was 92%, in MTBE it dropped to 26% when using 2-AlTUD-1 as catalyst.
- Simons, Chretien,Hanefeld, Ulf,Arends, Isabel W. C. E.,Sheldon, Roger A.,Maschmeyer, Thomas
-
p. 5829 - 5835
(2007/10/03)
-
- Rh-catalysed asymmetric hydrogenations with a dynamic library of chiral tropos phosphorus-ligands
-
A number of homo- (16) and heterocombinations (115) of chiral tropos phosphorus-ligands were screened for the rhodium catalysed asymmetric hydrogenation of methyl N-acetamido acrylate, resulting in the identification of an extremely effective and enantioselective (100% yield, 94% ee) phosphite/phosphoramidite heterocombination. A library of 16 chiral tropos phosphorus-ligands, based on a chiral P-bound alcohol or secondary amine and a flexible (tropos) P-bound biphenol unit, was synthesised. This ligand library allowed the screening of 16 homocombinations and 115 heterocombinations for the rhodium catalysed asymmetric hydrogenation of methyl N-acetamido acrylate. The screening resulted in the identification of a phosphite/phosphoramidite heterocombination, which proved to be extremely effective and enantioselective (100% yield, 94% ee).
- Monti, Chiara,Gennari, Cesare,Piarulli, Umberto
-
p. 6859 - 6862
(2007/10/03)
-
- Synthesis of a novel spiro bisphosphinamidite ligand for highly enantioselective hydrogenation
-
A novel chiral bisphosphinamidite ligand SpiroNP has been synthesized. The rhodium complex of this ligand has been found to be highly active and enantioselective in the asymmetric hydrogenation of (Z)-2-acetamidoacrylic acid derivatives and α,β-unsaturated carboxylic acid derivatives.
- Lin, Ching Wen,Lin, Chi-Ching,Lam, Louis F.-L.,Au-Yeung, Terry T.-L.,Chan, Albert S.C.
-
p. 7379 - 7381
(2007/10/03)
-
- Optically pure 1,2-bis[(o-alkylphenyl)phenylphosphino]ethanes and their use in rhodium-catalyzed asymmetric hydrogenations of α-(acylamino)acrylic derivatives
-
Optically pure (S,S)-1,2-bis[(o-alkylphenyl)-phenylphosphino]ethanes 1a-d were prepared in four steps from phenyldichlorophosphine via phosphine-boranes as the intermediates. The rhodium complexes 5a-d of these diphosphines were used for the asymmetric hydrogenations of α-(acylamino)-acrylic derivatives including β-disubstituted derivatives. Markedly high enantioselectivity (78→99%) was observed for the reduction of β-monosubstituted derivatives. β-Disubstituted derivatives were also reduced in considerably high enantioselectivity (up to 90%). The single crystal X-ray analysis of the rhodium complex 5c of (S,S)-1,2-bis[phenyl(5′,6′,7′,8′- tetrahydronaphthyl)phosphino]ethane (1c) revealed its δ-type structure with face orientation of the two tetrahydronaphthyl groups and edge orientation of the two phenyl groups. This conformation corresponds to that of the rhodium complex of 1,2-bis[(o-methoxyphenyl)phenylphosphino]ethane (DIPAMP); the rhodium complex of (R,R)-DIPAMP, whose chirality at phosphorus is opposite that of 5c, exhibits a λ-type structure with the face orientation of the two o-methoxyphenyl groups and the edge orientation of the two phenyl groups. The conformational similarity of these rhodium complexes as well as the stereochemical outcome in the asymmetric hydrogenations means that the coordinative interaction of the methoxy group of DIPAMP with rhodium metal is not the main factor that affects asymmetric induction.
- Wada, Yoshiyuki,Imamoto, Tsuneo,Tsuruta, Hideyuki,Yamaguchi, Kentaro,Gridnev, Ilya D.
-
p. 777 - 788
(2007/10/03)
-