Enantioselektive Katalyse, 4. Synthese N‐substituierter (R,R)‐3,4‐Bis(diphenylphosphino)‐pyrrolidine und Anwendung ihrer Rhodiumkomplexe zur asymmetrischen Hydrierung von α‐(Acylamino)acrylsäure‐Derivaten

Nagel, Ulrich; Kinzel, E.; Andrade, Juan G.; Prescher, G.

doi:10.1002/cber.19861191112

Cited by 156 publications

(53 citation statements)

References 18 publications

(1 reference statement)

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“…The reaction of (3R,4R)3,4-bis(diphenylphosphino)-pyrrolidine (Pyrphos, R,R-1) [12] with commercially available 1-pyrenebutyric acid in the presence of 1,3-dicyclohexylcarbodiimine (DCC) and 4-(dimethyl-A C H T U N G T R E N N U N G amino)pyridine (DMAP) afforded ligand (R,R)-2 in high yield (94%). [13] When evaluating the performance of ligand (R,R)-2 in the Rh(I)-catalyzed asymmetric hydrogenation of a-dehydroamino esters 3, we found that the introduction of a pyrenyl group into the Pyrphos ligand did not affect its enantioselectivity (Table 1).…”

Section: Communicationsmentioning

confidence: 99%

Simply Modified Chiral Diphosphine: Catalyst Recycling via Non‐covalent Absorption on Carbon Nanotubes

et al. 2008

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A new type of recyclable chiral catalyst system was developed by absorption of pyrenemodified Pyrphos rhodium catalyst onto carbon nanotubes via p-p stacking interaction. This modified catalyst was successfully applied in the asymmetric hydrogenation of a-dehydroamino esters for nine cycles without obvious deterioration of activity and enantioselectivity.Keywords: absorption; asymmetric catalysis; carbon nanotube; catalyst recycling; pyrene Asymmetric catalysis is a powerful, economically feasible tool for the synthesis of optically active molecules that serve as precursors for pharmaceuticals, agrochemicals, and flavorings, as well as functional materials. Many efficient, homogeneous chiral catalysts that exhibit high activities and enantioselectivities have been developed in the past few decades. [1] However, the considerable difficulty involved in separating these expensive chiral catalysts from products for reuse has restricted their applications in industrial processes.The immobilization of chiral catalysts on various insoluble solid supports such as inorganic materials, organic polymers, or membranes can solve the problems arising from homogeneous catalysis.[2] However, these "heterogenized" catalysts usually suffer from decreased catalytic activities and enantioselectivities due to restriction by the solid matrix, which limits mobility and accessibility of the active sites. Thus, chiral catalysts that combine the advantages of homogeneous catalysts (high catalytic activity and enantioselectivity) and heterogeneous catalysts (easy separation and convenient recycling of the catalyst from the reaction mixture) have become a focus of intense research in recent years. For example, Chan and co-workers reported the synthesis of a soluble polyester-supported BINAP ligand based on the concept of "one-phase catalysis and two-phase separation". This supported chiral ligand showed a higher activity than the corresponding "free" ligand in the Ru(II)-catalyzed asymmetric hydrogenation of a-(6-methoxyl-2-naphthyl)-A C H T U N G T R E N N U N G acrylic acid. [3] Recent advances such as thermomorphic catalyst systems, [4] dendritic catalysts, [5] magnetically recoverable catalysts, [6] and self-assembled supported catalysts [7] have provided interesting alternatives for recovering and reusing chiral catalysts. However, the sophisticated designs generally result in increased cost of the chiral catalyst and/or catalyst system. In this communication, we describe a very simple and efficient approach to recycle and reuse a chiral Rh(I)/diphosphine catalyst for asymmetric hydrogenation via non-covalent absorption on carbon nanotubes (CNTs).Since their discovery in 1991, CNTs have attracted considerable attention because of their unique mechanical, electronic, and chemical stability properties.[8] These properties have made CNTs very promising nanomaterials for many applications in chemistry.[9] However, only a few applications of CNTs in catalytic asymmetric reactions have been reported. García and co-workers [10] util...

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Section: Communicationsmentioning

confidence: 99%

Simply Modified Chiral Diphosphine: Catalyst Recycling via Non‐covalent Absorption on Carbon Nanotubes

et al. 2008

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“…Contrary to the previous experience in the synthesis of pyrrolidine diphosphines with non-aromatic amines [18], the synthesis of (R,R)-N-phenyl-3,4-bis(diphenylphosphino)pyrrolidine (2) using an aromatic amine posed quite a few problems, requiring the use of specific reduction conditions, use of the trifliloxy leaving group instead of the mesyloxy and use of the more reactive potassium diphenylphosphide instead of the in situ prepared sodium diphenylphosphide. The newly established synthetic sequence is outlined in Scheme 1.…”

Section: Ligand Synthesismentioning

confidence: 88%

“…However, looking at the structure of 2 determined by X-ray crystallography and comparing it with the structures of analogous pyrrolidine diphosphines [18,[24][25][26][27], of which 1 is an example, we observed significant explanatory differences.…”

Section: Enantioselective Catalysis Experimentsmentioning

confidence: 91%

“…The phenyl group directly bonded to the nitrogen in 2 confers upon this atom significant sp 2 character as can be confirmed by bond angles C1A-N1-C5, 122.5(3); C1A-N1-C2, 124.2(3); and C5-N1-C2, 112.5(3) as well as the N1-C1A bond length, 137.0(5) pm. Unlike other known pyrrolidine ligands [18,[24][25][26][27] this new chiral ligand NPPP has a quasi coplanar arrangement of the two rings which imposes an extended rigidity upon the ligand. However, what was expected to be a favourable characteristic proved not to contribute to the efficient induction of chirality, as shown by the transfer hydrogenation results presented.…”

Section: Enantioselective Catalysis Experimentsmentioning

confidence: 95%

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(R,R)-N-phenyl-3,4-bis(diphenylphosphino)pyrrolidine: an N-aryl pyrrolidine ligand for enantioselective transfer hydrogenation

Gonsalves

Serra

Silva

et al. 2001

Journal of Molecular Catalysis A: Chemical

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The N-aryl pyrrolidine diphosphine (R,R)-N-phenyl-3,4-bis(diphenylphosphino)pyrrolidine was obtained from natural tartaric acid. Contrary to our preliminary expectations, this new chiral ligand proved to be less selective than the corresponding N-benzyl pyrrolidine diphosphine. An attempted explanation of the observed behaviour based on the stereochemistry of the ligand as shown by X-ray crystallography is presented.

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“…The reactions were run at 50 bar hydrogen pressure for 24 h. After identification of the most promising catalysts by HPLC analysis of the reaction products the results were confirmed by upscaling and performance of the hydro- genation in individual trials. Among 48 ligands tested Prophos [18] and DeguPHOS [19] were superior and induced enantioselectivities of 40 ± 60% ee in the product. The most efficient reaction was achieved by application of a catalyst which was obtained from [Rh(COD) 2 ]OTf and (R)-NORPHOS.…”

Section: Mechanistic Investigationsmentioning

confidence: 99%

Asymmetric Cleavage of Racemic 1,3‐Oxazolidines – A New Dynamic Process in Homogeneous Rh(I)‐Catalyzed Hydrogenation

Tararov

Kadyrov²,

Monsees³

et al. 2003

Adv Synth Catal

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The mechanism of the homogeneously catalyzed hydrogenation of 1,3-oxazolidines with a Rh(I) diphosphane catalyst affording tertiary hydroxyethyl-substituted amines was investigated with the help of D 2 labelling experiments. It was found that the reaction proceeds via prochiral intermediates with, preferentially, an iminium cation being in equilibrium with the 1,3-oxazolidine. This observation opened up the opportunity to run the reaction stereoselectively by employment of a racemic 1,3-oxazolidine and a chiral catalyst. By means of high-throughput screening considering 144 catalysts a cationic Rh(NOR-PHOS)-complex was identified as the most efficient catalyst, which afforded after optimization of solvent, temperature and H 2 pressure the corresponding chiral hydroxyethylamine in 95% yield and 80% ee.

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Enantioselektive Katalyse, 4. Synthese N‐substituierter (R,R)‐3,4‐Bis(diphenylphosphino)‐pyrrolidine und Anwendung ihrer Rhodiumkomplexe zur asymmetrischen Hydrierung von α‐(Acylamino)acrylsäure‐Derivaten

Cited by 156 publications

References 18 publications

Simply Modified Chiral Diphosphine: Catalyst Recycling via Non‐covalent Absorption on Carbon Nanotubes

Simply Modified Chiral Diphosphine: Catalyst Recycling via Non‐covalent Absorption on Carbon Nanotubes

(R,R)-N-phenyl-3,4-bis(diphenylphosphino)pyrrolidine: an N-aryl pyrrolidine ligand for enantioselective transfer hydrogenation

Asymmetric Cleavage of Racemic 1,3‐Oxazolidines – A New Dynamic Process in Homogeneous Rh(I)‐Catalyzed Hydrogenation

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