Palladium-catalyzed arylation of unsymmetrical olefins. Bidentate phosphine ligand controlled regioselectivity

Cabri, Walter; Candiani, Ilaria; Bedeschi, Angelo; Santi, R.

doi:10.1021/jo00039a011

Cited by 175 publications

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“…This result is in agreement with later calculations by Green et al [137] on the oxidative addition of chlorobenzene: the tricoordinated, T-shaped [(ItBu)Pd(Cl)Ph] (169, Figure 7) complex was found to be more stable by 39 kJ mol À1 with NHC and Cl in a trans position. With the exception of X = triflate, [238] Pd À X bonds are stronger than Pd-phosphine bonds. Therefore, in the course of the reaction one phosphane ligand (L) is expected to dissociate to free a site for coordination of the alkene.…”

Section: Carbopalladations Of Alkenes and The Heck-mizoroki Reactionmentioning

confidence: 96%

Palladium Complexes of N‐Heterocyclic Carbenes as Catalysts for Cross‐Coupling Reactions—A Synthetic Chemist's Perspective

2007

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Palladium-catalyzed C-C and C-N bond-forming reactions are among the most versatile and powerful synthetic methods. For the last 15 years, N-heterocyclic carbenes (NHCs) have enjoyed increasing popularity as ligands in Pd-mediated cross-coupling and related transformations because of their superior performance compared to the more traditional tertiary phosphanes. The strong sigma-electron-donating ability of NHCs renders oxidative insertion even in challenging substrates facile, while their steric bulk and particular topology is responsible for fast reductive elimination. The strong Pd-NHC bonds contribute to the high stability of the active species, even at low ligand/Pd ratios and high temperatures. With a number of commercially available, stable, user-friendly, and powerful NHC-Pd precatalysts, the goal of a universal cross-coupling catalyst is within reach. This Review discusses the basics of Pd-NHC chemistry to understand the peculiarities of these catalysts and then gives a critical discussion on their application in C-C and C-N cross-coupling as well as carbopalladation reactions.

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Section: Carbopalladations Of Alkenes and The Heck-mizoroki Reactionmentioning

confidence: 96%

Palladium Complexes of N‐Heterocyclic Carbenes as Catalysts for Cross‐Coupling Reactions—A Synthetic Chemist's Perspective

2007

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“…Das Ergebnis wurde später durch Rechnungen von Green et al [137] für die oxidative Addition von Chlorbenzol bestätigt: Der dreifach koordinierte, T-förmige Komplex [(ItBu)Pd(Cl)Ph] (169, Abbildung 7) war mit NHC und Cl in trans-Stellung um 39 kJ mol À1 stabiler. Pd-X-Bindungen sind, mit Ausnahme von X = Triflat [238] , stärker als Palladium-Phosphan-Bindungen. ).…”

Section: G Organ Et Alunclassified

Aus der Sicht des Synthetikers: Palladiumkomplexe N‐heterocyclischer Carbene als Katalysatoren für Kreuzkupplungen

2007

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Palladiumkatalysierte C‐C‐ und C‐N‐Kupplungen zählen zu den vielseitigsten und leistungsfähigsten Syntheseverfahren. Seit 15 Jahren erfreuen sich die N‐heterocyclischen Carbene (NHCs) wachsender Beliebtheit als Liganden für palladiumvermittelte Kreuzkupplungen und ähnliche Methoden. Sie sind in vielerlei Hinsicht den üblichen tertiären Phosphanen überlegen. Weil NHCs stark σ‐elektronenschiebend sind, können sie auch anspruchsvolle Substrate zu oxidativen Insertionen bewegen. Andererseits führen ihre Sperrigkeit und ihre besondere Topologie zu einer raschen reduktiven Eliminierung. Schließlich tragen die starken Pd‐NHC‐Bindungen zur hohen Stabilität der aktiven Spezies bei – auch bei niedrigen Ligand/Pd‐Verhältnissen und hohen Temperaturen. Wenn erst stabile, anwenderfreundliche und leistungsstarke NHC‐Pd‐Präkatalysatoren kommerziell verfügbar sind, liegt das Ziel eines universellen Kreuzkupplungskatalysators in greifbarer Nähe. Dieser Aufsatz beschreibt zunächst die chemischen Grundlagen zu den NHC‐Pd‐Komplexen, um ihre Besonderheiten kennenzulernen. Anschließend folgt eine umfassende Diskussion zur Anwendung dieser Katalysatoren in C‐C‐ und C‐N‐Kreuzkupplungen sowie in der Carbopalladierung.

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“…[21] For Heck reactions with electron-rich alkenes it has been proposed that the b-arylation occurred through an ionic pathway and the g-arylation takes place via a neutral mechanism, although steric effects can also be responsible. [21][22][23][24] The ionic pathway is mainly observed when the halide anion is not bonded to Pd(II). This is the case when silver or thallium salts are added, when employing triflates as arylating reagents, when using halide-free ionic liquids as solvents, or when adding diphosphines, such as 1,3-bis(diphenylphosphino)propane or 1,1'-bis(diphenylphosphino)ferrocene.…”

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confidence: 99%

“…This is the case when silver or thallium salts are added, when employing triflates as arylating reagents, when using halide-free ionic liquids as solvents, or when adding diphosphines, such as 1,3-bis(diphenylphosphino)propane or 1,1'-bis(diphenylphosphino)ferrocene. [24] On the other hand, the isomerization process can be avoided by working in halide-free ionic liquids to give g-arylated allyl alcohols, such as 5 and 10. [21] In our laboratory we have been working on the use of oxime-derived palladacycles as a source of highly active zero-valent palladium nanoparticles for phosphine-free C À C bond forming reactions, Heck, Suzuki, Stille, Ullmann, Cassar-Heck-Sonogashira, Scheme 1.…”

mentioning

confidence: 99%

Arylation of Allyl Alcohols in Organic and Aqueous Media Catalyzed by Oxime‐Derived Palladacycles: Synthesis of β‐Arylated Carbonyl Compounds

Alacid

Nájera

2007

Adv Synth Catal

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A 4-hydroxyacetophenone oxime-derived palladacycle catalyzes the Mizoroki-Heck reaction of allyl alcohols with aryl iodides, bromides, and chlorides in aqueous and organic solvents. The reaction takes place in the presence of dicyclohexylmethylamine or cesium carbonate as bases, the addition of tetrabutylammonium bromide (TBAB) as additive for aryl bromides and chlorides being necessary. Under these reaction conditions, b-arylated aldehydes and ketones are mainly obtained using a rather low loading of palladium (0.1-1 mol %). Similar catalytic activity is shown by a Kaiser oxime resin-derived palladacycle, which allows one to perform recycling and reusing experiments with low Pd leaching. The high regio-and chemoselectivity observed supported that these palladacycles, working as a source of Pd(0) species, operates mainly through a neutral mechanism. This methodology has been applied to the synthesis of important b-arylated carbonyl compounds, such as 4-phenylbutan-2-one, 4-(4-hydroxyphenyl)butan-2-one, dihydrochalcones, the anti-inflamatory nabumetone, and the fragance blilial . g-Arylation is observed in the reactions of allyl alcohol and but-3-en-2-ol with 2-iodoaniline giving mainly the corresponding quinolines. The same tendency is observed in the case of 1,1-dimethylallyl alcohol affording either g-arylated alcohols or (E)-1-arylisoprenes.

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Palladium-catalyzed arylation of unsymmetrical olefins. Bidentate phosphine ligand controlled regioselectivity

Cited by 175 publications

References 0 publications

Palladium Complexes of N‐Heterocyclic Carbenes as Catalysts for Cross‐Coupling Reactions—A Synthetic Chemist's Perspective

Palladium Complexes of N‐Heterocyclic Carbenes as Catalysts for Cross‐Coupling Reactions—A Synthetic Chemist's Perspective

Aus der Sicht des Synthetikers: Palladiumkomplexe N‐heterocyclischer Carbene als Katalysatoren für Kreuzkupplungen

Arylation of Allyl Alcohols in Organic and Aqueous Media Catalyzed by Oxime‐Derived Palladacycles: Synthesis of β‐Arylated Carbonyl Compounds

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