Reversible Formation of a Cationic Palladium(II) Hydride [HPd(PPh
 3
 )
 2
 ]
 +
 in the Oxidative Addition of Acetic or Formic Acid to Palladium(0) in DMF

Amatore, Christian; Jutand, Anny; Meyer, Gilbert; Carelli, Italo; Chiarotto, Isabella

doi:10.1002/1099-0682(200008)2000:8<1855::aid-ejic1855>3.0.co;2-#

Cited by 49 publications

(21 citation statements)

References 35 publications

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“…Pd-hydride 22 can be formed by Pd(0) participating as a formal base to deprotonate acid 21 . 26 Importantly, the conjugate base of 21 then becomes the counterion associated with Pd-complex 22 . Hydropalladation of allene 4 likely occurs at the less hindered unsubstituted olefin of the allene from either the top or bottom face of the allene π-system.…”

Section: Resultsmentioning

confidence: 99%

The Palladium Catalyzed Asymmetric Addition of Oxindoles and Allenes: An Atom-Economical Versatile Method for the Construction of Chiral Indole Alkaloids

2011

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The Pd-catalyzed asymmetric allylic alkylation (AAA) is one of the most useful and versatile methods for asymmetric synthesis known in organometallic chemistry. Development of this reaction over the past 30 years has typically relied on the use of an allylic electrophile bearing an appropriate leaving group to access the reactive Pd(π-allyl) intermediate that goes on to the desired coupling product after attack by the nucleophile present in the reaction. Our group has been interested in developing alternative approaches to access the reactive Pd(π-allyl) intermediate that does not require the use of an activated electrophile, which ultimately generates a stoichiometric byproduct in the reaction that is derived from the leftover leaving group. Along these lines, we have demonstrated that allenes can be used to generate the reactive Pd(π-allyl) intermediate in the presence of an acid cocatalyst, and this system is compatible with nucleophiles to allow for formation of formal AAA products by Pd-catalyzed additions to allenes. This article describes our work regarding the use of oxindoles as carbon-based nucleophiles in a Pd-catalyzed asymmetric addition of oxindoles to allenes (Pd-catalyzed hydrocarbonation of allenes). By using the chiral standard Trost ligand (L1) and 3-aryloxindoles as nucleophiles, this hydrocarbonation reaction provides products with two vicinal stereocenters, with one being quaternary, in excellent chemo-, regio-, diastereo-, and enantioselectivities in high chemical yields.

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Section: Resultsmentioning

confidence: 99%

The Palladium Catalyzed Asymmetric Addition of Oxindoles and Allenes: An Atom-Economical Versatile Method for the Construction of Chiral Indole Alkaloids

2011

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“…Protonation with two equivalents of acetic acid regenerates the Pd(OAc) 2 –NHC complex F and completes the catalytic cycle. While the precise role(s) of added acetic acid is not defined, added acetic acid could affect the turnover of the Pd 0 –NHC peroxo intermediate E , reprotonation of Pd–alkoxide B , or an equilibrium between Pd–hydride C and Pd 0 species D 13…”

Section: Methodsmentioning

confidence: 99%

A Well‐Defined Complex for Palladium‐Catalyzed Aerobic Oxidation of Alcohols: Design, Synthesis, and Mechanistic Considerations

Jensen¹,

Schultz²,

Mueller³

et al. 2003

Angew Chem Int Ed

299

106

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“…The hydride [Pd II H(PPh 3 ) 2 (DMF)] + with acetate or formate counterions is in equilibrium with Pd(PPh 3 ) 3 and acetic acid (pK a DMF 12.6) 15 in DMF with an equilibrium constant of about 125, and with formic acid (pK a DMF 11.6) 15 with K 250. 303 The pK a LAC of [PdH(PPh 3 ) 3 ] + is predicted to be 9 (not listed the Table). The deprotonation of [PtH(PPh 3 ) 3 ] + by ethanolic KOH to produce Pt(PPh 3 ) 3 was reported in 1966.…”

Section: Other Complexesmentioning

confidence: 99%

Brønsted–Lowry Acid Strength of Metal Hydride and Dihydrogen Complexes

2016

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Transition metal hydride complexes are usually amphoteric, not only acting as hydride donors, but also as Brønsted-Lowry acids. A simple additive ligand acidity constant equation (LAC for short) allows the estimation of the acid dissociation constant Ka(LAC) of diamagnetic transition metal hydride and dihydrogen complexes. It is remarkably successful in systematizing diverse reports of over 450 reactions of acids with metal complexes and bases with metal hydrides and dihydrogen complexes, including catalytic cycles where these reactions are proposed or observed. There are links between pKa(LAC) and pKa(THF), pKa(DCM), pKa(MeCN) for neutral and cationic acids. For the groups from chromium to nickel, tables are provided that order the acidity of metal hydride and dihydrogen complexes from most acidic (pKa(LAC) -18) to least acidic (pKa(LAC) 50). Figures are constructed showing metal acids above the solvent pKa scales and organic acids below to summarize a large amount of information. Acid-base features are analyzed for catalysts from chromium to gold for ionic hydrogenations, bifunctional catalysts for hydrogen oxidation and evolution electrocatalysis, H/D exchange, olefin hydrogenation and isomerization, hydrogenation of ketones, aldehydes, imines, and carbon dioxide, hydrogenases and their model complexes, and palladium catalysts with hydride intermediates.

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Reversible Formation of a Cationic Palladium(II) Hydride [HPd(PPh ₃ ) ₂ ] ⁺ in the Oxidative Addition of Acetic or Formic Acid to Palladium(0) in DMF

Cited by 49 publications

References 35 publications

The Palladium Catalyzed Asymmetric Addition of Oxindoles and Allenes: An Atom-Economical Versatile Method for the Construction of Chiral Indole Alkaloids

The Palladium Catalyzed Asymmetric Addition of Oxindoles and Allenes: An Atom-Economical Versatile Method for the Construction of Chiral Indole Alkaloids

A Well‐Defined Complex for Palladium‐Catalyzed Aerobic Oxidation of Alcohols: Design, Synthesis, and Mechanistic Considerations

Brønsted–Lowry Acid Strength of Metal Hydride and Dihydrogen Complexes

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Reversible Formation of a Cationic Palladium(II) Hydride [HPd(PPh 3 ) 2 ] + in the Oxidative Addition of Acetic or Formic Acid to Palladium(0) in DMF

Cited by 49 publications

References 35 publications

The Palladium Catalyzed Asymmetric Addition of Oxindoles and Allenes: An Atom-Economical Versatile Method for the Construction of Chiral Indole Alkaloids

The Palladium Catalyzed Asymmetric Addition of Oxindoles and Allenes: An Atom-Economical Versatile Method for the Construction of Chiral Indole Alkaloids

A Well‐Defined Complex for Palladium‐Catalyzed Aerobic Oxidation of Alcohols: Design, Synthesis, and Mechanistic Considerations

Brønsted–Lowry Acid Strength of Metal Hydride and Dihydrogen Complexes

Contact Info

Product

Resources

About

Reversible Formation of a Cationic Palladium(II) Hydride [HPd(PPh ₃ ) ₂ ] ⁺ in the Oxidative Addition of Acetic or Formic Acid to Palladium(0) in DMF