SPANphos: A C2‐Symmetric trans‐Coordinating Diphosphane Ligand

Freixa, Zoraida; Beentjes, Mark S.; Batema, Guido D.; Dieleman, Cedric B.; Strijdonck, Gino P. F. van; Reek, Joost N. H.; Kamer, Paul C. J.; Fraanje, Jan; Leeuwen, Piet W. N. M. van

doi:10.1002/ange.200390301

Cited by 55 publications

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References 18 publications

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“…Thus, trans-[PdCl 2 (SPANphos)] reported by van Leeuwen does not show any tendency to cis-trans isomerization [10], the complex trans-[PdCl 2 (diphos)] (diphos = 2,6-bis(2-((diphenylphosphino)methyl)phenyl)benzene) reported by Protasiewicz [11] has been successfully used as Heck and Suzuki catalyst, in spite of the rigid trans-geometry [12]. With the diphosphine Xantphos, developed by van Leeuwen [13] and used as a ligand for Suzuki reactions, palladium complexes with trans-standing alkyl and chloro ligands [14] and with trans-standing aryl and bromo ligands [15] have been isolated and characterized by X-ray crystallography.…”

Section: Introductionmentioning

confidence: 74%

“…Recently, several palladium(II) complexes containing trans-spanning diphosphine ligands, that contain a rigid ligand backbone, have been synthesized [10,11,16]. Thus, trans-[PdCl 2 (SPANphos)] reported by van Leeuwen does not show any tendency to cis-trans isomerization [10], the complex trans-[PdCl 2 (diphos)] (diphos = 2,6-bis(2-((diphenylphosphino)methyl)phenyl)benzene) reported by Protasiewicz [11] has been successfully used as Heck and Suzuki catalyst, in spite of the rigid trans-geometry [12].…”

Section: Introductionmentioning

confidence: 99%

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Square-planar dichloro palladium complexes with trans-configurated phosphine ligands avoiding ortho-metallation: Ligand design, complex synthesis, molecular structure and catalytic potential for Suzuki cross-coupling reactions

Chahen

Therrien

Süß‐Fink

2006

Journal of Organometallic Chemistry

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The square-planar palladium complexes trans-[PdCl 2 (PPh 2 -CH 2 -2,4,6-C 6 H 2 Me 3 ) 2 ] (1) and trans-[PdCl 2 (g 2 -PPh 2 -CH 2 -2,4,6-C 6 HMe 3 -CH 2 -2,4,6-C 6 HMe 3 -CH 2 -PPh 2 )] (2) have been synthesized from [PdCl 2 (cod)] (cod = 1,5-cyclooctadiene) and the corresponding new phosphine or diphosphine ligands. The single-crystal X-ray structure analysis reveals for both complexes a trans arrangement of the two chlorine and of the two phosphorus atoms. In both cases, ortho-metallation leading to palladacycles is not possible, since all ortho positions in the benzylic rings of 1 and 2 are blocked by methyl substituents. Both complexes are found to catalyze Suzuki cross-coupling reactions of deactivated and even bulky arene substrates.

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Section: Introductionmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Square-planar dichloro palladium complexes with trans-configurated phosphine ligands avoiding ortho-metallation: Ligand design, complex synthesis, molecular structure and catalytic potential for Suzuki cross-coupling reactions

Chahen

Therrien

Süß‐Fink

2006

Journal of Organometallic Chemistry

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“…Solche auf einer Spiro-2,2'-bichroman-Struktur basierende Liganden haben sich bereits in asymmetrischen Reaktionen bewährt. [11] Mit diesem Protokoll werden durchweg hervorragende Resultate erzielt (hohe Ausbeuten, hohe Enantio-und DiaSchema 1. Beispiele von Naturstoffen mit [5,6]-Spiroketaleinheiten.…”

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Einfach und dennoch herausfordernd: Neues zur asymmetrischen Synthese von Spiroketalen

Wilsdorf

Reißig

2012

Angewandte Chemie

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Spiroketale sind in Naturstoffen häufig vorkommende Strukturelemente. Nicht selten sind sie die pharmakophoren Gruppen, die die biologischen Eigenschaften der Verbindungen maßgeblich bestimmen. Die Vielfalt reicht von einfachen chiralen Verbindungen bis zu komplexen Spiroketalpolyketiden, z. B. Reveromycin B (1).[1] Spiroketale mit anellierten aromatischen Gruppen (hier verkürzt: aromatische Spiroketale) sind als Bestandteile von Naturstoffen deutlich seltener, aber es gibt sehr prominente und interessante Beispiele wie Berkelsäure (2) und g-Rubromycin (3; Schema 1). Übersichtsartikel aus den letzten Jahren [2] bieten einen Einblick in alle bis dahin erfolgreich abgeschlossenen Totalsynthesen von Naturstoffen, die aromatische [5,5] Ein erster Schritt in diese Richtung gelang nun Ding et al.[6] mit der enantioselektiven Synthese aromatischer Spiroketale. Angeregt durch Arbeiten der Gruppen von Bolm [7] und Hou [8] und aufbauend auf den eigenen Erfahrungen mit Iridium(I)-katalysierten Hydrierungen von Ketiminen [9] und a-aryl-b-substituierten Acrylsäuren [10] untersuchten sie eine asymmetrische katalytische Hydrierung von a,a'-Bis(2-hydroxyaryliden)ketonen des Typs 4, der eine diastereoselektive Cyclisierung zu aromatischen [6,6]-Spiroketalen 6 unmittelbar folgt (Schema 2).Die Reaktionssequenz beginnt mit der enantioselektiven Reduktion des prochiralen a,b-ungesättigten Ketons 4 zum chiralen 2,6-trans-disubstituierten Cyclohexanon 5. Hierfür haben sich Iridium(I)-Komplexe mit Phosphan-Oxazolin-Liganden [(P,N)-Hybridliganden] als effiziente Katalysatoren erwiesen. Besonders bewährt hat sich der (S,S)-SpinPHOXLigand (Schema 2), der exzellente Enantioselektivitäten und Ausbeuten liefert. Die sich unmittelbar anschließende Spiroketalisierung verläuft hoch diastereoselektiv und wird vermutlich durch eine Iridium(III)-Spezies katalysiert, die sich mit Wasserstoff in situ bildet. Kontrollexperimente belegen diese Vermutung. Ein interessantes Beispiel, das Ding et al. beschreiben, ist die Folgereaktion des dibromsubstituierten Derivats 7 zum neuartigen chiralen Diphosphanliganden 8 (Schema 3). Solche auf einer Spiro-2,2'-bichroman-Struktur basierende Liganden haben sich bereits in asymmetrischen Reaktionen bewährt. [11] Mit diesem Protokoll werden durchweg hervorragende Resultate erzielt (hohe Ausbeuten, hohe Enantio-und DiaSchema 1. Beispiele von Naturstoffen mit [5,6]-Spiroketaleinheiten.

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“…Still, the best results for the Suzuki cross-coupling of the deactivated and sterically hindered aryl bromide with aryl boronic acid have been obtained by Buchwald and coworkers [4] with ligands avoiding palladacycles formation. Recently, several palladium(II) complexes containing trans-spanning diphosphine ligands that contain a rigid ligand backbone have been synthesized [5,6]. Thus, trans-[PdCl 2 (SPANphos)] reported by van Leeuwen does not show any tendency to cis-trans isomerization [5], the complex trans-[PdCl 2 -(diphos)] (diphos = 2,6-bis(2-((diphenylphosphino)methyl)phenyl)benzene) reported by Protasiewicz [6] has been successfully used as Heck and Suzuki catalyst, in spite of the rigid trans-geometry [7].…”

mentioning

confidence: 99%

“…Recently, several palladium(II) complexes containing trans-spanning diphosphine ligands that contain a rigid ligand backbone have been synthesized [5,6]. Thus, trans-[PdCl 2 (SPANphos)] reported by van Leeuwen does not show any tendency to cis-trans isomerization [5], the complex trans-[PdCl 2 -(diphos)] (diphos = 2,6-bis(2-((diphenylphosphino)methyl)phenyl)benzene) reported by Protasiewicz [6] has been successfully used as Heck and Suzuki catalyst, in spite of the rigid trans-geometry [7]. With the diphosphine Xantphos, developed by van Leeuwen [8] and used as a ligand for Suzuki reaction, palladium complexes with trans-standing alkyl and chloro ligands [9] and with trans-standing aryl and bromo ligands [10] have been isolated and characterized by X-ray crystallography.…”

mentioning

confidence: 99%

Double HCl elimination and configuration change in the square-planar palladium complex trans-[{(Ph2PC6H4CONH)2C6H4}PdCl2] under Suzuki conditions: Isolation and molecular structure of cis-[{(Ph2PC6H4CON)2C6H4}Pd]

Chahen

Karmazin-Brelot

Süß‐Fink

2006

Inorganic Chemistry Communications

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The trans-configurated square-planar palladium complex trans-[{(Ph 2 PC 6 H 4 CONH) 2 C 6 H 4 }PdCl 2 ] (1), which catalyzes the Suzuki cross coupling of 4-bromotoluene with phenylboronic acid, was found to react with potassium carbonate in toluene at 90°C (Suzuki conditions) to give cis-[{(Ph 2 PC 6 H 4 CON) 2 C 6 H 4 }Pd] (2). The single-crystal X-ray structure analysis of 2 reveals the square-planar palladium center to be in a cis configuration. The trans-cis configuration change at palladium is possible because of the elimination of two HCl equivalents in the conversion of 1 into 2. Both complexes 1 and 2 show approximately the same catalytic performance for Suzuki reactions, suggesting 2 to be the catalytically active species.Keywords: Palladium complexes; Suzuki cross-coupling; Square-planar geometry; cis and trans configuration The Suzuki cross-coupling (Suzuki-Miyaura reaction), catalyzed by various palladium complexes, is among the most powerful synthetic tools for the generation of carbon-carbon bonds [1]. Although many different palladium(II) or palladium(0) complexes catalyze this coupling reaction, significant efforts have been put on the design of suitable ligands that can increase the catalytic activity of the palladium center. Some of the most active Suzuki catalysts are palladium complexes susceptible to ortho-metallation or palladacycle formation [2,3]. Still, the best results for the Suzuki cross-coupling of the deactivated and sterically hindered aryl bromide with aryl boronic acid have been obtained by Buchwald and coworkers [4] with ligands avoiding palladacycles formation. Recently, several palladium(II) complexes containing trans-spanning diphosphine ligands that contain a rigid ligand backbone have been synthesized [5,6]. Thus, trans-[PdCl 2 (SPANphos)] reported by van Leeuwen does not show any tendency to cis-trans isomerization [5], the complex trans-[PdCl 2 -(diphos)] (diphos = 2,6-bis(2-((diphenylphosphino)methyl)phenyl)benzene) reported by Protasiewicz [6] has been successfully used as Heck and Suzuki catalyst, in spite of the rigid trans-geometry [7]. With the diphosphine Xantphos, developed by van Leeuwen [8] and used as a ligand for Suzuki reaction, palladium complexes with trans-standing alkyl and chloro ligands [9] and with trans-standing aryl and bromo ligands [10] have been isolated and characterized by X-ray crystallography. Since we recently synthesized a square planar

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SPANphos: A C₂‐Symmetric trans‐Coordinating Diphosphane Ligand

Cited by 55 publications

References 18 publications

Square-planar dichloro palladium complexes with trans-configurated phosphine ligands avoiding ortho-metallation: Ligand design, complex synthesis, molecular structure and catalytic potential for Suzuki cross-coupling reactions

Square-planar dichloro palladium complexes with trans-configurated phosphine ligands avoiding ortho-metallation: Ligand design, complex synthesis, molecular structure and catalytic potential for Suzuki cross-coupling reactions

Einfach und dennoch herausfordernd: Neues zur asymmetrischen Synthese von Spiroketalen

Double HCl elimination and configuration change in the square-planar palladium complex trans-[{(Ph2PC6H4CONH)2C6H4}PdCl2] under Suzuki conditions: Isolation and molecular structure of cis-[{(Ph2PC6H4CON)2C6H4}Pd]

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