Asymmetric Catalysis Using Self-Assembled Chiral Bidentate <i>P,P</i>-Ligands

Takacs, James M.; Reddy, D. S.; Moteki, Shin A.; Wu, Di; Palencia, Hector

doi:10.1021/ja049873+

Cited by 161 publications

(43 citation statements)

References 20 publications

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“…In a typical experiment, the high pressure NMR tube was filled with 30 lmol of [Rh(acac)(CO) 2 ], 75 lmol of phosphite zinc(II) porphyrin, 75 lmol phosphine and 1.5 ml of toluene-d 8 . The tube was purged three times with 15 bar of CO/H 2 (1:1), pressurized to approximately 20 bar, heated to 80°C and incubated for 1 h. Measurements were performed at 25°C.…”

Section: High-pressure Nmr-experimentsmentioning

confidence: 99%

“…Interestingly, the selectivities observed for the hydroformylation of alkenes by the chelating supramolecular ligand are comparable with the best traditional covalent bidentate ligands. Takcas et al [8] prepared a library of chiral diphosphite ligands based on phosphite functionalized chiral bisoxazoline ligands via the assembly of heteroleptic zinc complexes. The library of palladium catalysts was explored for allylic alkylation reaction and interestingly enantiomeric excesses between 20% and 99% were observed.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Supraphos: A supramolecular strategy to prepare bidentate ligands

Reek¹,

Röder²,

Goudriaan³

et al. 2005

Journal of Organometallic Chemistry

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Herein, we report a new strategy for the preparation of chelating bidentate ligands, which involves the mixing of two mondentate ligands functionalized with complementary binding sites. The assembly process is based on selective metal-ligand interactions employing phosphite zinc(II) porphyrins 1-6 and the nitrogen-containing phosphorus ligands b-i (Scheme 1). Only 14 monodentate ligands were utilized to generate a library of 48 palladium catalysts based on supraphos-type bidentate ligands. The characterization of rhodium complexes based on representative Supramolecular bidentate ligands and the comparison of their performance in the hydroformylation of styrene will be presented. The current library of catalysts was tested in the asymmetric palladium-catalyzed alkylation of rac-1,3-diphenyl-2-propenyl acetate, which resulted in a large variety in the observed enantioselectivity for the different catalysts. Importantly, small variations in the supraphos building blocks, lead to large differences in the enantioselectivity imposed by the catalyst, the most selective catalyst producing 97% ee.

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Section: High-pressure Nmr-experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Supraphos: A supramolecular strategy to prepare bidentate ligands

Reek¹,

Röder²,

Goudriaan³

et al. 2005

Journal of Organometallic Chemistry

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“…Ligandenkombination [b] T [35,36] Eine Bibliothek von 50 Heterodimerkombinationen aus den Untereinheiten 55-61 A und B wurde in der Palladiumkatalysierten asymmetrischen allylischen Aminierung des racemischen Carbonats 62 zum Allylsulfonamid 63 getestet (Schema 11). Unter den 50 Ligandkombinationen variierten die Enantioselektivitäten zwischen 20 und 97 % ee.…”

Section: Koordinative Bindungen Als Ligand-ligand-wechselwirkungenunclassified

Supramolekulare Ansätze zur Erzeugung von Bibliotheken zweizähniger Chelatliganden für die homogene Katalyse

Breit

2005

Angewandte Chemie

120

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Die kombinatorische Katalysatorentwicklung und ‐optimierung leidet bislang an der schlechten Zugänglichkeit strukturell diverser Ligandenbibliotheken, vor allem für die Klasse der strukturell komplexeren Chelatliganden. Ein völlig neuer Ansatz umgeht das Problem der schwierigen Ligandensynthese durch die Selbstorganisation von strukturell einfacheren einzähnigen Liganden zu zweizähnigen Liganden durch anziehende nichtkovalente Ligand‐Ligand‐Wechselwirkungen. Bei Verwendung komplementärer Ligand‐Ligand‐Bindungsmotive führt schon einfaches Mischen von jeweils zwei unterschiedlichen einzähnigen Liganden zum Aufbau von Bibliotheken definierter Chelatligand‐Katalysatoren. Dieser Kurzaufsatz fasst die ersten Ansätze und Ergebnisse in diesem vielversprechenden Forschungsgebiet der homogenen Katalyse zusammen.

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“…In both instances, the strength of the Lewis acid-base interaction, reinforced by two strong rhodium-phosphorus bonds, sufficed to keep the structure intact under catalytic conditions, but certainly stronger interactions were desirable. The use of ionic interactions is one way to achieve more stable assemblies [15][16][17][18][19][20]. Recently we introduced rigid bis-cationic Zn II (Robson macrocycles) as templates that form supramolecular bidentate Bidentate ligands templated by a convex trimetallic bis(salphen) platform ligands by assembly with both neutral and anionic Lewis basefunctionalized phosphines [21].…”

Section: Introductionmentioning

confidence: 99%

Bidentate ligands templated by a convex trimetallic bis(salphen) platform

Freixa¹,

Ponsico²,

Frischmann³

et al. 2012

Supramolecular Catalysis

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A Zn 3 -bis(salphen) compound was used as a template for the construction of bidentate phosphine ligands by self-assembly with phosphines containing a carboxyl group. The convex shape of the template, exposing the three zinc atoms, ensured the correct orientation of the assembled diphosphine, such that it can coordinate to a single metal atom. The strong zinc-carboxylate bond guaranteed the integrity of the final assembly at the low concentrations (1 mM) used in catalysis. Depending on the substitution pattern of the benzoic acid phosphines, either monometallic chelates or dimeric complexes were formed. Coordination studies were carried out for Pt and Rh. A modest chelate effect in the rhodium catalyzed hydroformylation of 1-octene (l/b=4.7) confirmed the formation of the bidentate assemblies.

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Asymmetric Catalysis Using Self-Assembled Chiral Bidentate P,P-Ligands

Cited by 161 publications

References 20 publications

Supraphos: A supramolecular strategy to prepare bidentate ligands

Supraphos: A supramolecular strategy to prepare bidentate ligands

Supramolekulare Ansätze zur Erzeugung von Bibliotheken zweizähniger Chelatliganden für die homogene Katalyse

Bidentate ligands templated by a convex trimetallic bis(salphen) platform

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