- Inducing Axial Chirality in a Supramolecular Catalyst
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A new type of ligand, which is able to form axially chiral, supramolecular complexes was designed using DFT calculations. Two chiral monomers, each featuring a covalently bound chiral auxiliary, form a bidentate phosphine ligand with a twisted, hydrogen-bonded backbone upon coordination to a transition metal center which results in two diastereomeric, tropos complexes. The ratio of the diastereomers in solution is very temperature- and solvent-dependent. Rhodium and platinum complexes were analyzed through a combination of NMR studies, ESI-MS measurements, as well as UV-VIS and circular dichroism spectroscopy. The chiral self-organized ligands were evaluated in the rhodium-catalyzed asymmetric hydrogenation of α-dehydrogenated amino acids and resulted in good conversion and high enantioselectivity. This research opens the way for new ligand designs based on stereocontrol of supramolecular assemblies through stereodirecting chiral centers.
- Wenz, Katharina Marie,Leonhardt-Lutterbeck, Günter,Breit, Bernhard
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- Topology-Based Functionalization of Robust Chiral Zr-Based Metal-Organic Frameworks for Catalytic Enantioselective Hydrogenation
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The design and development of robust and porous supported catalysts with high activity and selectivity is extremely significant but very challenging for eco-friendly synthesis of fine chemicals and pharmaceuticals. We report here the design and synthesis of highly stable chiral Zr(IV)-based MOFs with different topologies to support Ir complexes and demonstrate their network structures-dependent asymmetric catalytic performance. Guided by the modulated synthesis and isoreticular expansion strategy, five chiral Zr-MOFs with a flu or ith topology are constructed from enantiopure 1,1′-biphenol-derived tetracarboxylate linkers and Zr6, Zr9, or Zr12 clusters. The obtained MOFs all show high chemical stability in boiling water, strongly acidic, and weakly basic aqueous solutions. The two flu MOFs featuring the dihydroxyl groups of biphenol in open and large cages, after sequential postsynthetic modification with P(NMe2)3 and [Ir(COD)Cl]2, can be highly efficient and recyclable heterogeneous catalysts for hydrogenation of α-dehydroamino acid esters with up to 98% ee, whereas the three ith MOFs featuring the dihydroxyl groups in small cages cannot be installed with P(NMe2)3 to support the Ir complex. Incorporation of Ir-phosphorus catalysts into Zr-MOFs leads to great enhancement of their chemical stability, durability, and even stereoselectivity. This work therefore not only advances Zr-MOFs as stable supports for labile metal catalysts for heterogeneous asymmetric catalysis but also provides a new insight into how highly active chiral centers can result due to the framework topology.
- Jiang, Hong,Zhang, Wenqiang,Kang, Xing,Cao, Ziping,Chen, Xu,Liu, Yan,Cui, Yong
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supporting information
p. 9642 - 9652
(2020/07/02)
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- Enantiodivergent asymmetric catalysis with the tropos BIPHEP ligand and a proline derivative as chiral selector
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A catalytic system based on the tropos ligand BIPHEP and (S)-proline methyl ester as chiral selector was studied for Rh-catalysed asymmetric catalysis. By careful control of the catalyst preformation conditions, the enantioselectivity could be completely reversed in asymmetric hydrogenation of prochiral olefins maintaining the same absolute level in favorable cases. The enantiodivergent asymmetric catalysis could be rationalised by the interplay of the dynamic chirality (tropos) of the phosphine ligand and the coordination of the proline selector. Treating a suitable Rh-BIPHEP precursor with the (Sc)-proline-based ionic liquid led to an equimolar mixture of (RaSc)- and (SaSc)-diastereomers that is kinetically stable at 0 °C. At higher temperature, an irreversible diastereomerisation process was observed resulting in the diastereomerically pure (RaSc)-complex [Rh{(Ra)-BIPHEP}{(Sc)-ProlOMe}]. Whereas the use of the pure (RaSc)-complex led to 51% ee (R) in the hydrogenation of methyl 2-acetamidoacrylate, the S-product was formed with almost identical enantioselectivity when the (RaSc)/(SaSc)-mixture was applied under identical conditions. This inversion was associated with the relative stability of the diastereomers in the equilibria forming the catalytically active substrate complex. The possibility to use this different reactivity to control the direction of enantioselectivity was demonstrated for the hydrogenation of different substrates whereby ee's of up to 80% could be achieved. Moreover, the (RaSc)-complex led to high enantioselectivities of up 86% ee in the asymmetric hydroboration of styrene, approaching the performance of the atropos BINAP ligand for this reaction.
- Oczipka,Müller,Leitner,Franciò
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p. 678 - 683
(2015/12/30)
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- Stitching phospholanes together piece by piece: New modular di- and tridentate stereodirecting ligands
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The modular one-pot synthesis of a large family of bi- and tridentate 2,5-dimethyl- and 2,5-diphenyl-substituted phospholanes employs air-stable chiral phospholanium chloride salts and primary amines or NH4Cl as starting materials. These were t
- Lloret Fillol, Julio,Kruckenberg, Achim,Scherl, Peter,Wadepohl, Hubert,Gade, Lutz H.
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supporting information; experimental part
p. 14047 - 14062
(2012/01/13)
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- Novel and efficient chiral bisphosphorus ligands for rhodium-catalyzed asymmetric hydrogenation
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(Figure Presented) A series of structurally novel, operationally convenient, and efficient chiral 2-phosphino-2,3-dihydrobenzo[d][1,3] oxaphosphole ligands was developed. Applications of ligands 3a and 3b in rhodium-catalyzed asymmetric hydrogenation of α-(acylamlno)acrylates andβ-(acylamino)acrylates provided excellent enantioselectivities (up to >99% ee) and reactivities (up to 10 000 TON).
- Tang, Wenjun,Capacci, Andrew G.,White, Andre,Ma, Shengli,Rodriguez, Sonia,Qu, Bo,Savoie, Jolaine,Patel, Nitinchandra D.,Wei, Xudong,Haddad, Nizar,Grinberg, Nelu,Yee, Nathan K.,Krishnamurthy, Dhileepkumar,Senanayake, Chris H.
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supporting information; experimental part
p. 1104 - 1107
(2010/06/13)
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- Modular monodentate phosphoramidite ligands for rhodium-catalyzed enantioselective hydrogenation
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A new class of monodentate phosphoramidite ligands (DpenPhos) has been developed on the basis of the modular concept for Rh(I)-catalyzed asymmetric hydrogenations of a variety of olefin derivatives, affording the corresponding optically active compounds in excellent yields and enantioselectivities. The ligands have the advantages of facile preparation, tunable structure, and broad scope of substrates in their Rh(I) complex-catalyzed asymmetric hydrogenations. Copyright
- Liu, Yan,Ding, Kuiling
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p. 10488 - 10489
(2007/10/03)
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- 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
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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.
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p. 9603 - 9611
(2007/10/03)
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- Rhodium-catalyzed asymmetric hydrogenation of functionalized olefins using monodentate spiro phosphoramidite ligands
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Novel chiral monodentate phosphorus ligands, SIPHOS, were conveniently synthesized from 1,1′-spirobiindane-7,7′-diol. The Rh complexes of SIPHOS can catalyze the hydrogenation of α-dehydroamino esters in mild conditions, providing α-amino acid derivatives
- Fu, Yu,Guo, Xun-Xiang,Zhu, Shou-Fei,Hu, Ai-Guo,Xie, Jian-Hua,Zhou, Qi-Lin
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p. 4648 - 4655
(2007/10/03)
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- New perfluoroalkylated BINAP usable as a ligand in homogeneous and supercritical carbon dioxide asymmetric hydrogenation
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New (R)- or (S)-4,4′- and 5,5′- perfluoroalkylated BINAP have been synthesized in four steps from enantiomerically pure BINAP. These new ligands were used in the homogeneous asymmetric hydrogenation of ethyl acetoacetate in ethanol and in the asymmetric hydrogenation of methyl-2-acetamidoacrylate in supercritical carbon dioxide. In the supercritical media, the addition and nature of a co-solvent have been discussed. Very good conversion and selectivity were obtained in each case.
- Berthod, Mikael,Mignani, Gerard,Lemaire, Marc
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p. 1121 - 1126
(2007/10/03)
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- Self-supported heterogeneous catalysts for enantioselective hydrogenation
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"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
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p. 10524 - 10525
(2007/10/03)
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- Application of chiral mixed phosphorus/sulfur ligands to enantioselective rhodium-catalyzed dehydroamino acid hydrogenation and ketone hydrosilylation processes
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Chiral mixed phosphorus/sulfur ligands 1-3 have been shown to be effective in enantioselective Rh-catalyzed dehydroamino acid hydrogenation and ketone hydrosilylation reactions (eqs 1, 2). After assaying the influence of the substituents at sulfur, the substituents on the ligand backbone, the relative stereochemistry within the ligand backbone, and the substituents at phosphorus, ligands 2c (R = 3,5-dimethylphenyl) and 3 were found to be optimal in the Rh-catalyzed hydrogenation of a variety of α-acylaminoacrylates in high enantioselectivity (89-97% ee). A similar optimization of the catalyst for the Rh-catalyzed hydrosilylation of ketones showed that ligand 3 afforded the highest enantioselectivities for a wide variety of aryl alkyl and dialkyl ketones (up to 99% ee). A model for asymmetric induction in the hydrogenation reaction is discussed in the context of existing models, based on the absolute stereochemistry of the products and the X-ray crystal structures of catalyst precursors and intermediates.
- Evans, David A.,Michael, Forrest E.,Tedrow, Jason S.,Campos, Kevin R.
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p. 3534 - 3543
(2007/10/03)
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- Novel monodentate spiro phosphorus ligands for rhodium-catalyzed hydrogenation reactions
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Novel monodentate phosphorus ligands containing the 1,1′-spirobiindane backbone have been synthesized and applied in the asymmetric rhodium-catalyzed hydrogenation of functionalized olefins, providing excellent enantioselectivities (up to 99.3% ee).
- Fu, Yu,Xie, Jian-Hua,Hu, Ai-Guo,Zhou, Hai,Wang, Li-Xin,Zhou, Qi-Lin
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p. 480 - 481
(2007/10/03)
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- Catalytic asymmetric hydrogenation of α-(acetamido)acrylates using TRAP trans-chelating chiral bisphosphine ligands: Remarkable effects of ligand P-substituent and hydrogen pressure on enantioselectivity
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The catalytic asymmetric hydrogenation of α-(acetamido)acrylates was carded out with the rhodium complexes prepared from [Rh(cod)2]BF4 and trans-chelating chiral bisphosphine ligands, (S,S)-2,2'-bis[(R)-1-(dialkylphosphino)ethyl]-1,1
- Kuwano,Sawamura,Ito
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p. 2571 - 2578
(2007/10/03)
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