Synthesis, X-ray Structures, NMR Studies and Density Functional Calculations of (η2-Fumarodinitrile)palladium(0) Complexes Containing Dihydro(phosphanylphenyl)oxazole Ligands

Zehnder, Margareta; Neuburger, Markus; Schaffner, Silvia; Jufer, Martin; Plattner, Dietmar A.

doi:10.1002/1099-0682(200206)2002:6<1511::aid-ejic1511>3.0.co;2-c

Cited by 12 publications

(2 citation statements)

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“…In order to relate the conformation of the ligand to the results of the catalytic reactions, the transition-state structures need to be considered. The stereochemistry-determining step is usually considered to have a late transition state, and the η 2 -olefin complexes resulting from nucleophilic attack on the allyl complexes should therefore be closer in structure to the transition state than the starting allyl complexes …”

Section: Resultsmentioning

confidence: 99%

Self-Adaptable Catalysts: Substrate-Dependent Ligand Configuration

et al. 2008

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Pd(II) allyl and Pd(0) olefin complexes containing the configurationally labile ligand 1,2-bis-[4,5-dihydro-3H-dibenzo[c-e]azepino]ethane were studied as models for intermediates in Pd-catalyzed allylic alkylations. According to NMR and DFT studies, the ligand prefers C(s) conformation in both eta3-1,3-diphenylpropenyl and eta3-cyclohexenyl Pd(II) complexes, whereas in Pd(0) olefin complexes it adopts different conformations in complexes derived from the two types of allyl systems in both solution and, as verified by X-ray crystallography, in the solid state. These results demonstrate that the Pd complex is capable of adapting its structure to the reacting substrate. The different structural preferences also provide an explanation for the behavior of 1,3-diphenyl-2-propenyl acetate and 2-cyclohexenyl acetate in Pd-catalyzed allylic alkylations using pseudo-C2 and pseudo-C(s) symmetric ligands.

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Section: Resultsmentioning

confidence: 99%

Self-Adaptable Catalysts: Substrate-Dependent Ligand Configuration

et al. 2008

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“…While a few isolable complexes of phosphinooxazoline (PHOX) type ligands to Pd(0) have been reported in the literature, 45,[49][50][51][52][53][54][55] accessing any isolable Pd complexes of the chiral diamide bisphosphine ligand platform -the eponymous Trost ligands -has proven particularly challenging (Figure 1B). Early work from Trost, Breit, and Organ established that mixing (S,S)-1,2-diaminocyclohexane-N,N'-bis (2diphenylphosphinobenzoyl) [(S,S)-Ph DACH, L1] with Pd2(dba)3 generates a species consistent with [L1]Pd(dba), exhibiting a κ 2 -(P,P) coordination mode; however, this species was not isolated.…”

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confidence: 99%

Active, selective, and stable single-component precatalysts for asymmetric allylic alkylation

Huang

Keenan

Richard

et al. 2023

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The stereoselective construction of new carbon-element bonds is a crucial aspect of organic synthesis. Among the many strategies developed to date, palladium-catalysed asymmetric allylic alkylation is commonly used to access chiral molecules in natural product and active pharmaceutical ingredient synthesis. The use of modular Trost-type ligands and phosphinooxazoline (PHOX) ligands results in generally high stereoselectivity for a wide range of transformations. However, these reactions nearly always require relatively high catalyst loadings (5-10 mol%), reaction-specific catalyst preactivation protocols, and excess chiral ligand to ensure high yield and selectivity. Here we report the isolation and catalytic evaluation of a series of chiral palladium(0) single-component precatalysts that are active for a variety of asymmetric allylic alkylation reactions. The four Trost-type precatalysts in this work are the first characterized examples of stable, isolable Pd complexes with the diphosphines coordinated in the desired κ2-P,P fashion. All of the palladium(0) complexes are stable for >12 months when stored under nitrogen, and can be handled as solids and even in solution under air for hours without decomposition. A catalytic evaluation of these single-component precatalysts across 9 distinct asymmetric allylic alkylation reactions reveals excellent performance in terms of reactivity, selectivity, practicality, and minimizing palladium and chiral ligand loading. This enables both small-scale multivariate screening studies and preparative scale synthesis of key chiral building blocks, exemplified with the unprecedented enantioselective allylation of hydantoins. The optimized reaction achieves high yield and enantioselectivity with only 0.2 mol% of catalyst (turnover number of 465). These precatalysts will enable development of more efficient and robust asymmetric allylic alkylation reactions toward complex target molecules.

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Kinetic Studies of the Oxidative Addition and Transmetallation Steps Involved in the Cross‐Coupling of Alkynyl Stannanes with Aryl Iodides Catalysed by η²‐(Dimethyl fumarate)(iminophosphane)palladium(0) Complexes

et al. 2004

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The complexes [Pd(η2‐dmfu)(P−N)] {dmfu = dimethyl fumarate; P−N = 2‐(PPh2)C6H4−1‐CH=NR, R = C6H4OMe‐4 (1a), CHMe2 (2a), C6H3Me2‐2,6 (3a), C6H3(CHMe2)2‐2,6 (4a)} undergo dynamic processes in solution which consist of a P−N ligand site exchange through initial rupture of the Pd−N bond at lower energy and an olefin dissociation‐association at higher energy. According to equilibrium constant values for olefin replacement, the complex [Pd(η2‐fn)(P−N)] (fn = fumaronitrile, 1b) has a greater thermodynamic stability than its dmfu analogue 1a. The kinetics of the oxidative addition of ArI (Ar = C6H4CF3‐4) to 1a and 2a lead to the products [PdI(Ar)(P−N)] (1c, 2c) and obey the rate law, kobs = k1A + k2A[ArI]. The k1A step involves oxidative addition to a reactive species [Pd(solvent)(P−N)] formed from dmfu dissociation. The k2A step is better interpreted in terms of oxidative addition to a species [Pd(η2‐dmfu)(solvent)(κ1‐P−N)] formed in a pre‐equilibrium step from Pd−N bond breaking. The complexes 1c and 2c react with PhC≡CSnBu3 in the presence of an activated olefin (ol = dmfu, fn) to yield the palladium(0) derivatives [Pd(η2‐ol)(P−N)] along with ISnBu3 and PhC≡CAr. The kinetics of the transmetallation step, which is rate‐determining for the overall reaction, obey the rate law: kobs = k2T[PhC≡CSnBu3]. The k2T values are markedly enhanced in more polar solvents such as CH3CN and DMF. The solvent effect and the activation parameters suggest an associative SE2 mechanism with substantial charge separation in the transition state. The kinetic data of the above reactions in various solvents indicate that, for the cross‐coupling of PhC≡CSnBu3 with ArI catalysed by 1a or 2a, the rate‐determining step is represented by the oxidative addition and that CH3CN is the solvent in which the highest rates are observed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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Synthesis, X-ray Structures, NMR Studies and Density Functional Calculations of (η2-Fumarodinitrile)palladium(0) Complexes Containing Dihydro(phosphanylphenyl)oxazole Ligands

Cited by 12 publications

References 47 publications

Self-Adaptable Catalysts: Substrate-Dependent Ligand Configuration

Self-Adaptable Catalysts: Substrate-Dependent Ligand Configuration

Active, selective, and stable single-component precatalysts for asymmetric allylic alkylation

Kinetic Studies of the Oxidative Addition and Transmetallation Steps Involved in the Cross‐Coupling of Alkynyl Stannanes with Aryl Iodides Catalysed by η²‐(Dimethyl fumarate)(iminophosphane)palladium(0) Complexes

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Synthesis, X-ray Structures, NMR Studies and Density Functional Calculations of (η2-Fumarodinitrile)palladium(0) Complexes Containing Dihydro(phosphanylphenyl)oxazole Ligands

Cited by 12 publications

References 47 publications

Self-Adaptable Catalysts: Substrate-Dependent Ligand Configuration

Self-Adaptable Catalysts: Substrate-Dependent Ligand Configuration

Active, selective, and stable single-component precatalysts for asymmetric allylic alkylation

Kinetic Studies of the Oxidative Addition and Transmetallation Steps Involved in the Cross‐Coupling of Alkynyl Stannanes with Aryl Iodides Catalysed by η2‐(Dimethyl fumarate)(iminophosphane)palladium(0) Complexes

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Kinetic Studies of the Oxidative Addition and Transmetallation Steps Involved in the Cross‐Coupling of Alkynyl Stannanes with Aryl Iodides Catalysed by η²‐(Dimethyl fumarate)(iminophosphane)palladium(0) Complexes