Development of Practical Rhodium Phosphine Catalysts for the Hydrogenation of β-Dehydroamino Acid Derivatives

Enthaler, Stephan; Erre, Giulia; Holz, Jens; Börner, Armin; Alberico, Elisabetta; Nieddu, Ilenia; Gladiali, Serafino; Beller, Matthias

doi:10.1021/op0602270

Cited by 41 publications

(13 citation statements)

References 68 publications

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“…A linear correlation was found, which is indicative of the monoligated nature of the Pd complex involved in the enantiodetermining C−H activation step. 30,31 This would also be consistent with the experiment performed with precatalyst 7, which showed results similar to the corresponding in situ Pd/ligand mixture (Table 3, entry 10).…”

Section: ■ Mechanistic Considerationssupporting

confidence: 89%

Efficient Pd⁰-Catalyzed Asymmetric Activation of Primary and Secondary C–H Bonds Enabled by Modular Binepine Ligands and Carbonate Bases

et al. 2015

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International audienceNew binepine ligands have been synthesized, and characterized and have been shown to induce high diastereo- and enantioselectivity in the intramolecular arylation of primary and secondary C(sp3)–H bonds, giving rise to fused cyclopentanes. The ligands were obtained as bench-stable phosphonium tetrafluoroborate salts that can be directly employed in catalysis. It was shown that a ferrocenyl P-substituent on the ligand allows achievement of high stereoselectivities in combination with potassium carbonate for the arylation of primary C–H bonds under unprecedentedly low temperature (90 °C) and catalyst loading (1–2 mol % Pd/2–3 mol % ligand). Using a base-free precatalyst, carbonate was shown to be the active base and to provide higher stereoselectivities than acetate and pivalate. The more difficult arylation of secondary C–H bonds could also be achieved and required fine-tuning of the ligand structure and the carbonate countercation. This method allowed generation of fused tricyclic products containing three adjacent stereocenters as single diastereoisomers and with moderate to high enantioselectivity. Experimental data indicated that the enantiodetermining C–H activation step involves a monoligated species. DFT (PBE0-D3) calculations were performed with a prototypical binepine ligand to understand the origin of the enantioselectivity. The preference for the major enantiomer was traced to the establishment of a more efficient network of weak attractive interactions between the phosphine ligand and the substrate

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Section: ■ Mechanistic Considerationssupporting

confidence: 89%

Efficient Pd⁰-Catalyzed Asymmetric Activation of Primary and Secondary C–H Bonds Enabled by Modular Binepine Ligands and Carbonate Bases

et al. 2015

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“…The least-substituted substrate methyl 2-(hydroxymethyl)acrylate (A; its product is also known as the Roche ester) [17] is used as a building block in the synthesis of the antitumor agents tedanolide and discodermolide. [18] The trisubstituted (unnatural) b-amino acid precursors (Z)methyl 3-acetamidobut-2-enoate (B) [19] and (E)-methyl 2-(acetamidomethyl)-3-phenylacrylate (C) [7j] are interesting building blocks for the synthesis of biologically active b-peptide chains, which are stable to proteolytic degradation. [20] Currently no efficient catalyst is reported to obtain C with high enantioselectivity.…”

Section: Resultsmentioning

confidence: 99%

Application of a Supramolecular‐Ligand Library for the Automated Search for Catalysts for the Asymmetric Hydrogenation of Industrially Relevant Substrates

Meeuwissen¹,

Kuil²,

Burg³

et al. 2009

Chemistry A European J

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A procedure is described for the automated screening and lead optimization of a supramolecular-ligand library for the rhodium-catalyzed asymmetric hydrogenation of five challenging substrates relevant to industry. Each catalyst is (self-) assembled from two urea-functionalized ligands and a transition-metal center through hydrogen-bonding interactions. The modular ligand structure consists of three distinctive fragments: the urea binding motif, the spacer, and the ligand backbone, which carries the phosphorus donor atom. The building blocks for the ligand synthesis are widely available on a commercial basis, thus enabling access to a large number of ligands of high structural diversity. The simple synthetic steps enabled the scale-up of the ligand synthesis to multigram quantities. For the catalyst screening, a library of twelve new chiral ligands was prepared that comprised substantial variation in electronic and steric properties. The automated procedures employed ensured the fast catalyst assembly, screening, and direct acquisition of samples for analysis. It appeared that the most selective catalyst was different for every substrate investigated and that small variations in the building blocks had a major impact on the catalyst performance. For two substrates, a catalyst was found that provided the product with outstanding enantioselectivity. The subsequent automated optimization of these two leads showed that an increase of catalyst loading, dihydrogen pressure, and temperature had a positive effect on the catalyst activity without affecting the catalyst selectivity.

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“…As already mentioned before, we were not able to identify a suited asymmetric catalyst for our previous [4+1]‐annulation of o ‐QMs 2 . However, given the fact that p ‐QM 3 a performed very well in the racemic reaction and also allowed for a catalytic approach, we were confident that the well‐described bulky chiral phosphines A or B may allow for a truly catalytic enantioselective protocol (Table ). We first used the binaphthyl‐based phosphines A1 – 3 , but unfortunately neither of them allowed for any product formation (entries 1–3).…”

Section: Resultsmentioning

confidence: 99%

Enantioselective Catalytic [4+1]‐Cyclization of ortho‐Hydroxy‐para‐Quinone Methides with Allenoates

Zielke

Kováč

Winter

et al. 2019

Chemistry A European J

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The first highly asymmetric catalytic synthesis of densely functionalized dihydrobenzofurans is reported, which starts from ortho ‐hydroxy‐containing para ‐quinone methides. The reaction relies on an unprecedented formal [4+1]‐annulation of these quinone methides with allenoates in the presence of a commercially available chiral phosphine catalyst. The chiral dihydrobenzofurans were obtained as single diastereomers in yields up to 90 % and with enantiomeric ratios up to 95:5.

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Development of Practical Rhodium Phosphine Catalysts for the Hydrogenation of β-Dehydroamino Acid Derivatives

Cited by 41 publications

References 68 publications

Efficient Pd⁰-Catalyzed Asymmetric Activation of Primary and Secondary C–H Bonds Enabled by Modular Binepine Ligands and Carbonate Bases

Efficient Pd⁰-Catalyzed Asymmetric Activation of Primary and Secondary C–H Bonds Enabled by Modular Binepine Ligands and Carbonate Bases

Application of a Supramolecular‐Ligand Library for the Automated Search for Catalysts for the Asymmetric Hydrogenation of Industrially Relevant Substrates

Enantioselective Catalytic [4+1]‐Cyclization of ortho‐Hydroxy‐para‐Quinone Methides with Allenoates

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Development of Practical Rhodium Phosphine Catalysts for the Hydrogenation of β-Dehydroamino Acid Derivatives

Cited by 41 publications

References 68 publications

Efficient Pd0-Catalyzed Asymmetric Activation of Primary and Secondary C–H Bonds Enabled by Modular Binepine Ligands and Carbonate Bases

Efficient Pd0-Catalyzed Asymmetric Activation of Primary and Secondary C–H Bonds Enabled by Modular Binepine Ligands and Carbonate Bases

Application of a Supramolecular‐Ligand Library for the Automated Search for Catalysts for the Asymmetric Hydrogenation of Industrially Relevant Substrates

Enantioselective Catalytic [4+1]‐Cyclization of ortho‐Hydroxy‐para‐Quinone Methides with Allenoates

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Efficient Pd⁰-Catalyzed Asymmetric Activation of Primary and Secondary C–H Bonds Enabled by Modular Binepine Ligands and Carbonate Bases

Efficient Pd⁰-Catalyzed Asymmetric Activation of Primary and Secondary C–H Bonds Enabled by Modular Binepine Ligands and Carbonate Bases