Modular Phospholane Ligands in Asymmetric Catalysis

Burk, Mark J.

doi:10.1021/ar990085c

Cited by 411 publications

(223 citation statements)

References 48 publications

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“…Contrary to the corresponding N-acyl enamide 19 however, reports of the successful hydrogenation of 22 are scarce. High ee's have been obtained using DuPhos 29 or TangPhos 30 as a ligand whereas monodentate phosphites have also been successful. 31 We decided to introduce enol carbamates as a new class of substrates to obtain enantiomerically enriched alcohols by asymmetric hydrogenation.…”

Section: Resultsmentioning

confidence: 99%

The Application of Monodentate Secondary Phosphine Oxide Ligands in Rhodium‐ and Iridium‐Catalyzed Asymmetric Hydrogenation.

et al. 2004

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The application of monodentate secondary phosphine oxide ligands in rhodium-and iridiumcatalyzed asymmetric hydrogenation Jiang, Xiao-bin; van den Berg, Michel; Minnaard, Adriaan; de Vries, Johannes G.; Feringa, B.L. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Abstract-Enantiopure secondary phosphine oxides have been tested as ligands in the rhodium-and iridium-catalyzed asymmetric hydrogenation of functionalized olefins. tert-Butylphosphinoyl benzene turned out to be a versatile ligand in the iridium-catalyzed hydrogenation of b-branched dehydroamino esters and in the rhodium-catalyzed hydrogenation of an enol carbamate.

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Section: Resultsmentioning

confidence: 99%

The Application of Monodentate Secondary Phosphine Oxide Ligands in Rhodium‐ and Iridium‐Catalyzed Asymmetric Hydrogenation.

et al. 2004

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“…, etc., were screened as ligands (56)(57)(58)(59)(60)(61)(62)(63)(64)(65). The detailed data are listed in Table 1.…”

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“…The results of using Ru-BINAP (56, 57), Bu-PQ-Phos (35,36), and Rh-Monophos (24) complexes as catalysts were rather disappointing, showing poor reactivities and enantioselectivities (Table 1, entries 1-9). Good improvement occurred by employing Rh-(Me-Duphos) (58) or Rh-Tangphos (59) complex in this reaction. Product 1a was isolated in almost quantitative yield with excellent enantioselectivity.…”

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Enantioselective hydrogenation of α-aminomethylacrylates containing a free NH group for the synthesis of β-amino acid derivatives

Qiu

Prashad

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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We describe highly enantioselective synthesis of ␤-amino acid derivatives (1a-c) using asymmetric hydrogenation of ␣-aminomethylacrylates (2a-c), which contain a free basic NOH group, as the key step. The ␣-aminomethylacrylates (2a-c) were prepared using the BaylisHillman reaction of an appropriate aldehyde with methyl acrylate followed by acetylation of the resulting allylic alcohols (4a-b) and S N2 -type amination of the allylic acetates (3a-b).asymmetric catalysis ͉ Baylis-Hillman reaction I n recent years, ␤-amino acids have received increasing attention as constituents of molecules with interesting biological and pharmacological activities (1-5) such as hypoglycemic and ketogenic activities. They are key moieties of a number of bioactive molecules, such as in taxol and in peptidic natural products with various enzyme inhibiting activities. Nonpeptidic ␤-amino acids are found in well known ␤-lactams. Considering their importance, asymmetric synthesis of enantiomerically pure ␤-amino acids has become an important challenge for organic chemists. The synthesis of enantiopure ␤-amino acids has been extensively studied (6-9). However, the known methods are mostly for the synthesis of ␤-substituted ␤-amino acids, and their preparation still suffers from a long synthetic sequence, low product yields, and laborious execution (10-14). For example, a recently reported synthesis of 1a involved nine steps from 3-phenylpropanoic acid (15-18). Peptide deformylase (PDF, EC 3.5.1.31), a metallopeptidase found in prokaryotic organisms, is essentially required for bacterial growth (19)(20)(21). Certain N-formyl hydroxylamine compounds were recently revealed to have good antibacterial function by means of their PDF-inhibiting capabilities. Chiral compounds 1, ␣-substituted ␤-amino acid derivatives, are key intermediates in the synthesis of this kind of compounds (15)(16)(17)(18)22). Their prochiral dehydroprecursors 2 could be prepared in high yields via a synthetic process shown in Scheme 1. Asymmetric hydrogenation of these substrates 2 is the simplest and most direct route to synthesize 1 because of its inherent efficiency and atom economy. In contrast to the great progress in the synthesis of ␤-substituted ␤-amino acids and derivatives via enantioselective hydrogenations (23-38), reports on the synthesis of ␣-substituted ␤-amino acids with this protocol are very limited. To the best of our knowledge, only one exceptional example has been given, very recently by Zheng and coworkers (38), using Rh-monophosphorus catalyst system for the hydrogenation of ␤-phthalimide acrylates. However, the activity of the catalyst was not high, and only E-isomers of substituted ␤-phthalimide acrylates were investigated. In fact, compounds 2 were a mixture of E-and Z-isomers formed in the synthesis, and they were not always easy to separate into single isomers. Generally, it is also difficult to achieve high activity and enantioselectivity for the system containing both isomers (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33). In light of the suc...

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“…Hence, intense research has been focused on the preparation of enantiomerically enriched unnatural ␣-amino acids, and, so far, several approaches, such as bioresolution routes (8)(9)(10)) and the rhodium-or rutheniumcatalyzed asymmetric hydrogenation of dehydroamino acids derivatives (11)(12)(13), have shown much promise. Nevertheless, there is still a great demand for more efficient and, especially, technically feasible methods for convenient construction of various types of rational designed unnatural amino acid derivatives.…”

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confidence: 99%

Catalytic asymmetric alkynylation of α-imino ester: A versatile approach to optically active unnatural α-amino acid derivatives

Chan

2005

Proc. Natl. Acad. Sci. U.S.A.

105

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The catalytic asymmetric introduction of alkynyl functionality to ␣-amino acid derivatives was realized by the direct addition of terminal alkynes to ␣-imino ester in the presence of chiral Cu(I) complex under mild reaction conditions. Owing to the rich chemistry to which alkyne can be subjected, the present system provides a remarkably versatile tool for the construction of optically active ␣-amino acid derivatives. Good yields and enantiomeric excess values were achieved with an array of terminal alkynes and challenging, biologically active, unnatural ␣-amino acid derivatives could be conveniently obtained. asymmetric catalysis Optically active nonproteinogenic ␣-amino acids are of exceptional and rapidly increasing popularity as important tools in protein engineering and peptide-based drug discovery due mainly to their implementation into nonscissile peptide mimics and peptide isosteres (1-7). Hence, intense research has been focused on the preparation of enantiomerically enriched unnatural ␣-amino acids, and, so far, several approaches, such as bioresolution routes (8-10) and the rhodium-or rutheniumcatalyzed asymmetric hydrogenation of dehydroamino acids derivatives (11-13), have shown much promise. Nevertheless, there is still a great demand for more efficient and, especially, technically feasible methods for convenient construction of various types of rational designed unnatural amino acid derivatives. In this regard, enantioselective nucleophilic addition to ␣-imino esters represents one of the most direct strategies (14), because a new chiral center and a new COC bond can be built in a single operation and an appropriately designed side chain can be introduced in the meantime. Previous work in this field mainly focused on the catalytic asymmetric alkylation of ␣-imino esters, in which enol silane (15-18), allyl-metal compounds (19,20), trimethylsilyl nitronate (21), ketone (22), and nitroalkane (23) have been used as nucleophiles.Recently, we reported the successful alkynylation of ␣-imino ester by demonstrating the feasibility of direct addition of terminal alkynes to ␣-imino ester 1 in the presence of Ag(I) salts under mild reaction conditions (Scheme 1) (24). In this process, a new bond between an sp 3 carbon and an sp carbon is formed.Capitalizing on this method, we envisioned an attractive route to optically active ␣-amino acid derivatives via the direct asymmetric alkynylation of ␣-imino ester. The following considerations are particularly noteworthy:1. The HC'C moiety is an excellent two-carbon medium for the delivery of biologically interesting units into the ␥-position of ␣-amino acids, because it could be easily hydrogenated to saturated status after completing the nucleophile role. In contrast, owing to the rich chemistry to which alkyne can be subjected, the presence of a C'C bond in the desired targets offers a unique and highly valuable opportunity for further synthetic elaboration on the ␤,␥-positions of ␣-amino acids. For example, semireduction of the products could directly afford vinyl...

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Modular Phospholane Ligands in Asymmetric Catalysis

Cited by 411 publications

References 48 publications

The Application of Monodentate Secondary Phosphine Oxide Ligands in Rhodium‐ and Iridium‐Catalyzed Asymmetric Hydrogenation.

The Application of Monodentate Secondary Phosphine Oxide Ligands in Rhodium‐ and Iridium‐Catalyzed Asymmetric Hydrogenation.

Enantioselective hydrogenation of α-aminomethylacrylates containing a free NH group for the synthesis of β-amino acid derivatives

Catalytic asymmetric alkynylation of α-imino ester: A versatile approach to optically active unnatural α-amino acid derivatives

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