Catalytic Enantioselective Arylboration of Alkenylarenes

Logan, Kaitlyn M.; Brown, M. Kevin

doi:10.1002/ange.201609844

Cited by 78 publications

(5 citation statements)

References 56 publications

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“…In the disclosure corresponding to the two-catalyst protocol 2 there is no mention of allyl–boron additions to electron-rich aryl alkenes or those involving more hindered (e.g., 2-substituted) electrophiles. Furthermore, enantioselective Cu–B(pin) or Cu–H additions with electron-deficient aryl olefins are either not mentioned 4,5,6,7,8 or found to be less enantioselective 9,10,11,12 (e.g., halo-, trifluoromethyl- or ester-substituted). It is unclear why enantioselectivity is lower with some substrates or at times depends on electrophile identity despite the fact that the Cu–B(pin)/Cu–H addition step is the stereochemistry-determining (e.g., 94% e.e.…”

mentioning

confidence: 99%

Mechanism-based enhancement of scope and enantioselectivity for reactions involving a copper-substituted stereogenic carbon centre

et al. 2017

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A rapidly emerging set of catalytic reactions involves intermediates that contain a copper-substituted stereogenic carbon centre. Here, we demonstrate that intimate understanding of this distinction provides ways for addressing limitations in reaction scope and explaining why unexpected variations in enantioselectivity often occur. By using catalytic enantioselective Cu–boryl addition to alkenes as the model process, we have been able to elucidate several key mechanistic principles. We show that higher electrophile concentration can lead to elevated enantioselectivity; this is because diastereoselective Cu–H elimination may be avoided and/or achiral Cu–boryl intermediates can be converted to allyl–B(pin) rather than add to an alkene. We illustrate that lower alkene amounts and/or higher chiral ligand concentration can minimize the deleterious influence of achiral Cu–alkyl species, resulting in improved enantiomeric ratios. Moreover, and surprisingly, we find that enantioselectivities are higher with the less reactive allylphenyl carbonates as chemoselective copper–hydride elimination is faster with an achiral Cu-alkyl species.

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confidence: 99%

Mechanism-based enhancement of scope and enantioselectivity for reactions involving a copper-substituted stereogenic carbon centre

et al. 2017

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“…Our studies begin with investigating the reaction of dienyl uoride E-1a with aldimine ester [38][39][40] 2a to generate α-alkenyl, α-methyl α-AA 3aa. Using the stereocontrol exhibited by Cuazomethine ylides in two-metal catalytic systems 47,48,52,[53][54][55] , we designed a synergistic Pd/Cu catalyst system [41][42][43][44][45][46][47][48][49][50][51][52] for controlling the stereochemistry of the newly formed chiral center by means of an appropriate combination of ligands on the two metals during the coupling step (Table 1). First, we tested Phosferrox Cu complex L1-Cu with Pd catalysts bearing a bisphosphine ligand (dppe, dppp, Xantphos, or DPEphos; L4-Pd-L7-Pd, respectively) and found that none of these combinations catalyzed the desired reaction (entries 1-4).…”

Section: Resultsmentioning

confidence: 99%

Synergistic Pd/Cu-Catalyzed Enantioselective Csp2–F Bond Alkylation of Fluoro-1,3-Dienes with Aldimine Esters

Zhang

2021

Preprint

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Due to the high energies of Csp2–F bonds, employing fluorinated compounds for Csp2–Csp3 coupling has been an unsolved challenge. In this work, we report an efficient protocol for enantioselective Csp2–Csp3 cross-coupling of dienyl fluorides with aldimine esters, which was enabled by a synergistic Cu/Pd catalysis. This reaction represents the first example of asymmetric Csp2–Csp3 cross-coupling involving an inert Csp2–F bond and provides expeditious access to chiral α-Alkenyl α-amino acids with high enantioselectivity. Control experiments suggest that the Csp2–F bond activation occurs through a pathway involving PdH migratory insertion and subsequent allylic defluorination, rather than by direct oxidative addition of the Csp2–F bond to Pd(0). The detailed mechanism was further investigated by DFT calculation and the enantioselectivity was rationalized.

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“…Through this mechanism, aryl electrophiles become suitable coupling partners in carboboration reaction, which is not trivial to achieve with Cu as the sole catalyst. [45] In addition, βhydride elimination is no longer a significant issue for the putative alkyl Pd(II) intermediates, as the alkyl group is predomintly carried by Cu in the form of alkylcuprate.…”

Section: Alkene Carboboration By Cooperative Catalysismentioning

confidence: 99%

Transition‐Metal‐Catalyzed 1,2‐Carboboration of Alkenes: Strategies, Mechanisms, and Stereocontrol

Liu

Gao

Zeng

et al. 2019

Israel Journal of Chemistry

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During the past decade, many research groups have described catalytic methods for 1,2-carboboration, allowing access to structurally complex organoboronates from alkenes. Various transition metals, especially copper, palladium, and nickel, have been widely used in these reactions. This review summarizes advances in this field, with a special focus on the catalytic cycles involved in different metal-catalyzed carboboration reactions, as well as the regio-and stereochemical consequences of the underlying mechanisms. 1,2-Carboboration of other unsaturated systems, such as alkynes and allenes, is outside of the scope of this review. Scheme 1. General depiction of catalyst-controlled 1,2-carboboration. In this scheme and throughout the manuscript, nucleophilic reaction partners are drawn in blue, and electrophilic reaction partners are drawn in red. Scheme 4. Cu(I)-catalyzed borylative radical cyclization. Scheme 5. Cu(I)-catalyzed intramolecular carboboration involving an aldol cyclization. Scheme 6. Cu(I)-catalyzed intramolecular acylboration.Review Isr. J. Chem. 2020, 60, 219 -229 Scheme 7. Cu(I)-catalyzed divergent alkylboration of alkenes. Scheme 8. Cu(I)-catalyzed alkene carboboration with aldehydes as the electrophile. Scheme 9. Cu(I)-catalyzed three-component acylboration. Scheme 10. Cu(I)-catalyzed heteroarylboration of 1,3-dienes.

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Catalytic Enantioselective Arylboration of Alkenylarenes

Cited by 78 publications

References 56 publications

Mechanism-based enhancement of scope and enantioselectivity for reactions involving a copper-substituted stereogenic carbon centre

Mechanism-based enhancement of scope and enantioselectivity for reactions involving a copper-substituted stereogenic carbon centre

Synergistic Pd/Cu-Catalyzed Enantioselective Csp2–F Bond Alkylation of Fluoro-1,3-Dienes with Aldimine Esters

Transition‐Metal‐Catalyzed 1,2‐Carboboration of Alkenes: Strategies, Mechanisms, and Stereocontrol

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