A New Method for High-Yield Cyclopalladation of Primary and Secondary Amines. Atom-Efficient Open-to-Air Inexpensive Synthesis of Buchwald-Type Precatalysts

Vicente, José; Saura‐Llamas, Isabel; Oliva-Madrid, María-José; Garcı́a-López, José-Antonio; Bautista, Delia

doi:10.1021/om200464s

Cited by 29 publications

(27 citation statements)

References 46 publications

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“…The model used for the DFT calculations so far in nonpolar solvents,22e, 33 [Pd(κ 2 ‐OAc)(κ 1 ‐OAc)(κ 1 ‐ N ‐aminoester)], does not correspond to the isolated neutral noncyclometalated dimers [Pd(μ‐OAc)(OAc)(NH 2 CH 2 Ar)] 2 , which have been found to be relevant intermediates in the orthopalladation of benzylamines and related species 12b. c If the use of such a model produces calculated data that fully agree with the experimental results, then species such as [Pd(κ 2 ‐OAc)(Cl)(κ 1 ‐ N ‐NH 2 CH 2 Ar)]20a can be considered as part of a valid model for the formation of the isolated compounds of type 3 indicated in Scheme . Similar compounds with mixtures of acetate/chloride ligands have also been found to be relevant for related metalation reactions 36.…”

Section: Resultsmentioning

confidence: 99%

Cyclopalladation and Reactivity of Amino Esters through CH Bond Activation: Experimental, Kinetic, and Density Functional Theory Mechanistic Studies

Laga

García‐Montero

Sayago

et al. 2013

Chemistry A European J

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The orthopalladation, through CH bond activation, of a large number of amino esters and amino phosphonates derived from phenylglycine, and having different substituents at the aryl ring and the C‐α atom, as well as on the N‐amine atom, has been studied. The experimental observations indicated an improvement in the yields of the orthopalladated compounds when the N‐amine and/or the C‐α atom are substituted, when compared with the unsubstituted methyl phenylglycinate derivatives. In contrast, substitutions at the aryl ring do not promote significant changes in the orthometalation results. Furthermore, the use of hydrochloride salts of the amino esters has also been shown to have a remarkably favorable effect on the process. All these observations have been fully quantified at different temperatures and pressures by a detailed kinetic study in solution in different solvents and in the presence and absence of added Brønsted acids and chloride anions. The data collected indicate relevant changes in the process depending on these conditions, as expected from the general background known for cyclopalladation reactions. An electronic mechanism of the orthopalladation has been proposed based on DFT calculations at the B3LYP level, and a very good agreement between the trends kinetically measured and the theoretically calculated activation barriers has been obtained. The reactivity of the new orthopalladated amino phosphonate derivatives has been tested and it was found that their halogenation, alkoxylation and carbonylation resulted in formation of the corresponding functionalized ortho‐haloaminophosphonates, ortho‐alkoxyaminophosphonates and oxoisoindolinylphosphonates.

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Section: Resultsmentioning

confidence: 99%

Cyclopalladation and Reactivity of Amino Esters through CH Bond Activation: Experimental, Kinetic, and Density Functional Theory Mechanistic Studies

Laga

García‐Montero

Sayago

et al. 2013

Chemistry A European J

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“…We should also highlight a recent report that describes the reaction of ammonium triflate derivatives from L-phenyalanine with palladium acetate, generating the corresponding cyclometalated complexes. 120 Even in this situation, where a proton blocks the directing group of the organic molecule, the existence of a species such as that indicated in Scheme 7 has been proposed, a clear indication of the determinant acceleration occurring on protonation of the abstracting ligand.…”

Section: Palladium(ii) Complexesmentioning

confidence: 99%

Kinetico-mechanistic studies of cyclometalating C–H bond activation reactions on Pd(ii) and Rh(ii) centres: The importance of non-innocent acidic solvents in the process

Granell

Martínez

2012

Dalton Trans.

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The activation of C-H bonds in homogeneous systems has been the subject of study for many years due to its involvement in important industrial catalytic processes. A large number of reviews on the different areas involved have appeared, but those dealing with kinetic studies, including activation parameters, are rather scarce due to the severe difficulties in interpreting experimental data. In this perspective, the information available from kinetico-mechanistic studies of cyclometalation reactions on Pd(II) and Rh(II) centres via C-H bond activation is considered. Experimental results from studies performed on complexes of these metal centres indicate that the historically accepted electrophilic substitution classification is not a satisfactory mechanistic term for the process occurring during the reaction. A definite acid-assisted phenomenon is evident for all the processes studied, which contradicts the expected need for a proton abstractor in the reaction. This is even more surprising when considering the expected hydrolysis of M-C bonds in such acidic media, indicating that metalation prevails under these conditions. Only the presence of coordinated acid molecules in solvolytic carboxylic acid media can explain the observations. The fine tuning between the proton abstraction capacity of a coordinated RCO(2)H molecule and its Lewis basicity results in a unique reactivity trend. DFT calculations carried out for these acid-assisted processes fully agree with the experimental trends observed.

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“…55 Despite the fact that cyclopalladation of tertiary amines is a long known reaction, 56 and a kinetico-mechanistic study has even been published, 57 cyclometallation of primary amines has received much less attention, even though a general method for their ortho-palladation has been described. 58 Besides this, the elegant isolation of a variety of dinuclear [Pd(AcO)(μ-AcO)L] 2 complexes (L being a primary amine), potential starting materials for the cyclometallated compounds, [59][60][61][62][63] is especially relevant.…”

Section: Introductionmentioning

confidence: 99%

A kinetico-mechanistic study on the C–H bond activation of primary benzylamines; cooperative and solid-state cyclopalladation on dimeric complexes

et al. 2014

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The cyclometallation reactions of dinuclear μ-acetato complexes of the type [Pd(AcO)(μ-AcO)L]2 (L = 4-RC6H4CH2NH2, R = H, Cl, F, CF3), a process found to occur readily even in the solid state, have been studied from a kinetico-mechanistic perspective. Data indicate that the dinuclear acetato bridged derivatives are excellent starting materials to activate carbon-hydrogen bonds in a facile way. In all cases the established concerted ambiphilic proton abstraction by a coordinated acetato ligand has been proved. The metallation has also been found to occur in a cooperative manner, with the metallation of the first palladium unit of the dimeric complex being rate determining; no intermediate mono-metallated compounds are observed in any of the processes. The kinetically favoured bis-cyclopalladated compound obtained after complete C-H bond activation does not correspond to the final isolated XRD-characterized complexes. This species, bearing the classical open-book dimeric form, has a much more complex structure than the final isolated compound, with different types of acetato ligands.

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A New Method for High-Yield Cyclopalladation of Primary and Secondary Amines. Atom-Efficient Open-to-Air Inexpensive Synthesis of Buchwald-Type Precatalysts

Cited by 29 publications

References 46 publications

Cyclopalladation and Reactivity of Amino Esters through CH Bond Activation: Experimental, Kinetic, and Density Functional Theory Mechanistic Studies

Cyclopalladation and Reactivity of Amino Esters through CH Bond Activation: Experimental, Kinetic, and Density Functional Theory Mechanistic Studies

Kinetico-mechanistic studies of cyclometalating C–H bond activation reactions on Pd(ii) and Rh(ii) centres: The importance of non-innocent acidic solvents in the process

A kinetico-mechanistic study on the C–H bond activation of primary benzylamines; cooperative and solid-state cyclopalladation on dimeric complexes

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