Unusual Allylpalladium Carboxylate Complexes: Identification of the Resting State of Catalytic Enantioselective Decarboxylative Allylic Alkylation Reactions of Ketones

Sherden, Nathaniel H.; Behenna, Douglas C.; Virgil, Scott C.; Stoltz, Brian M.

doi:10.1002/anie.200902575

Cited by 98 publications

(94 citation statements)

References 35 publications

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“…In previous experiments, we have found that ( S )- t -Bu-PHOX will generally prefer to incorporate the allyl group from the Re face 7 ; the predicted products are shown in Scheme 7. The high enantioselectivity observed for the minor product can be explained by considering the relative amount of each product and the competing modes of control (Figure 6).…”

Section: Resultsmentioning

confidence: 92%

“…The formation of a palladium carboxylate intermediate in our decarboxylative allylic alkylation has been supported by subsequent mechanistic studies performed by our laboratories. 7 Furthermore, the possibility that Pd(II) species formed in situ facilitate decarboxylation via Lewis acid type coordination (in a manner analogous to the Brønsted acid shown in Figure 2), can not be precluded.…”

Section: Resultsmentioning

confidence: 99%

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Palladium-catalyzed decarboxylative allylic alkylation of diastereomeric β-ketoesters

Reeves

Craig

et al. 2014

Tetrahedron

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The palladium-catalyzed decarboxylative allylic alkylation of diastereomeric β-ketoesters derived from 4-tert-butylcyclohexanone is described. These experiments were performed to elucidate our understanding of stereoablative enantioconvergent catalysis. A detailed analysis of the product distribution, including stereochemical outcome of the products, is included. These studies also reveal an interesting example of selectivity that is governed by competing modes of substrate and catalyst control.

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Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Palladium-catalyzed decarboxylative allylic alkylation of diastereomeric β-ketoesters

Reeves

Craig

et al. 2014

Tetrahedron

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“…In certain cases the chemical yields of the Pd-catalyzed allylic alkylation are somewhat modest. This is likely due to a combination of steric congestion and the opportunity for palladium-enolates to proceed through multiple catalytic pathways (inner sphere versus outer sphere alkylation chemistry), 22 some of which do not productively lead to the desired product (e.g., enolate protonation, 23 β-hydride elimination, 24 etc. ).…”

Section: Resultsmentioning

confidence: 99%

Enantioselective Construction of Acyclic Quaternary Carbon Stereocenters: Palladium-Catalyzed Decarboxylative Allylic Alkylation of Fully Substituted Amide Enolates

et al. 2017

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We report a divergent and modular protocol for the preparation of acyclic molecular frameworks containing newly created quaternary carbon stereocenters. Central to this approach is a sequence composed of a (1) regioselective and -retentive preparation of allyloxycarbonyltrapped fully-substituted stereodefined amide enolates and of a (2) enantioselective palladium-catalyzed decarboxylative allylic alkylation reaction using a novel bisphosphine ligand.

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“…4, Scheme 1). Not surprisingly, this class of reaction has also received considerable recent attention from the organic chemistry community [37][38][39][40]. However, the concept of using metal catalysts to selectively decompose esters is not new, and dates back over a century ago to Sabatier's work on the reactions of esters with metal oxide catalysts [41].…”

Section: Introductionmentioning

confidence: 99%

Gas-phase studies of metal catalyzed decarboxylative cross-coupling reactions of esters

O’Hair

2015

Pure and Applied Chemistry

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Metal-catalyzed decarboxylative coupling reactions of esters offer new opportunities for formation of C-C bonds with CO 2 as the only coproduct. Here I provide an overview of: key solution phase literature; thermochemical considerations for decarboxylation of esters and thermolysis of esters in the absence of a metal catalyst. Results from my laboratory on the use of multistage ion trap mass spectrometry experiments and DFT calculations to probe the gas-phase metal catalyzed decarboxylative cross-coupling reactions of allyl acetate and related esters are then reviewed. These studies have explored the role of the metal carboxylate complex in the gas phase decarboxylative coupling of allyl acetate proceeding via a simple twostep catalytic cycle. In Step 1, an organometallic ion, [CH 3 ML] +/-(where M is a group 10 or 11 metal and L is an auxillary ligand), is allowed to undergo ion-molecule reactions with allyl acetate to generate 1-butene and the metal acetate ion, [CH 3 CO 2 ML] +/-. In Step 2, the metal acetate ion is subjected to collision-induced dissociation to reform the organometallic ion and thereby close the catalytic cycle. DFT calculations have been used to explore the mechanisms of these reactions. The organometallic ions [CH 3 CuCH 3 ] -, [CH 3 Cu 2 ] + , [CH 3 AgCu] + and [CH 3 M(phen)] + (where M = Ni, Pd and Pt) all undergo C-C bond coupling reactions with allyl acetate (Step 1), although the reaction efficiencies and product branching ratios are highly dependant on the nature of the metal complex. For example, [CH 3 Ag 2 ] + does not undergo C-C bond coupling. Using DFT calculations, a diverse range of mechanisms have been explored for these C-C bond-coupling reactions including: oxidative-addition, followed by reductive elimination; insertion reactions and S N 2-like reactions. Which of these mechanisms operate is dependant on the nature of the metal complex. A wide range of organometallic ions can be formed via decarboxylation (Step 2) although these reactions can be in competition with other fragmentation channels. DFT calculations have located different types of transition states for the formation of [CH 3 CuCH 3 ] -, [CH 3 Cu 2 ] + , [CH 3 AgCu] + and [CH 3 M(phen)] + (where M = Ni, Pd and Pt). Of the catalysts studied to date, [CH 3 Cu 2 ] + and [CH 3 Pd(phen)] + are best at promoting C-C bond formation (Step 1) as well as being regenerated (Step 2). Preliminary results on the reactions of [C 6 H 5 M(phen)] + (M = Ni and Pd) with C 6 H 5 CO 2 CH 2 CH = CH 2 and C 6 H 5 CO 2 CH 2 C 6 H 5 are described.

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Unusual Allylpalladium Carboxylate Complexes: Identification of the Resting State of Catalytic Enantioselective Decarboxylative Allylic Alkylation Reactions of Ketones

Abstract: Palladium poprocks: Hold on to your CO2! Enantioselective Pd-catalyzed decarboxylative alkylation of ketone enolates proceeds via η1-σ-allyl Pd-carboxylate complexes by slow loss of CO2.

Cited by 98 publications

References 35 publications

Palladium-catalyzed decarboxylative allylic alkylation of diastereomeric β-ketoesters

Palladium-catalyzed decarboxylative allylic alkylation of diastereomeric β-ketoesters

Enantioselective Construction of Acyclic Quaternary Carbon Stereocenters: Palladium-Catalyzed Decarboxylative Allylic Alkylation of Fully Substituted Amide Enolates

Gas-phase studies of metal catalyzed decarboxylative cross-coupling reactions of esters

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