Mechanistic Studies of Pd(II)-Catalyzed <i>E</i>/<i>Z</i> Isomerization of Unactivated Alkenes: Evidence for a Monometallic Nucleopalladation Pathway

Matsuura, Rei; Karunananda, Malkanthi K.; Li, Mingyu; Nguyen, Nhi; Blackmond, Donna G.; Engle, Keary M.

doi:10.1021/acscatal.1c00783

Cited by 26 publications

(15 citation statements)

References 45 publications

(55 reference statements)

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“…To establish whether or not isomerization or C–H bond activation occurs on the alkenyl amine substrates, we carried out the reaction using deuterated trifluoroacetic acid in the absence of an aryl iodide coupling partner (Scheme a). After performing the reaction, we found that no alkene isomerization had occurred with the free amine as a directing group . Meanwhile, the trans -starting material was partially deuterated at the γ-position, while the cis -starting material was not.…”

Section: Methodology and Resultsmentioning

confidence: 97%

Palladium-Catalyzed γ,γ′-Diarylation of Free Alkenyl Amines

Landge

Grant

et al. 2021

J. Am. Chem. Soc.

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The direct difunctionalization of alkenes is an effective way to construct multiple C–C bonds in one-pot using a single functional group. The regioselective dicarbofunctionalization of alkenes is therefore an important area of research to rapidly obtain complex organic molecules. Herein, we report a palladium-catalyzed γ,γ′-diarylation of free alkenyl amines through interrupted chain walking for the synthesis of Z-selective alkenyl amines. Notably, while 1,3-dicarbofunctionalization of allyl groups is well precedented, the present disclosure allows 1,3-dicarbofunctionalization of highly substituted allylamines to give highly Z-selective trisubsubstituted olefin products. This cascade reaction operates via an unprotected amine-directed Mizoroki–Heck (MH) pathway featuring a β-hydride elimination to selectively chain walk to furnish a new terminal olefin which then generates the cis-selective alkenyl amines around the sterically crowded allyl moiety. This operationally simple protocol is applicable to a variety of cyclic, branched, and linear secondary and tertiary alkenylamines, and has a broad substrate scope with regard to the arene coupling partner as well. Mechanistic studies have been performed to help elucidate the mechanism, including the presence of a likely unproductive side C–H activation pathway.

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Section: Methodology and Resultsmentioning

confidence: 97%

Palladium-Catalyzed γ,γ′-Diarylation of Free Alkenyl Amines

Landge

Grant

et al. 2021

J. Am. Chem. Soc.

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“…[63] In contrast, 1,2-disubstituted internal alkenes exhibit low reactivity and provide a mixture of regio-and stereoisomers because the Mizoroki-Heck reaction with internal olefins produces a mixture of (E) and (Z)-products even from a single geometrical isomer. [64] Alternatively, allylic functionalization can proceed through a π-allyl palladium complex via a Tsuji-Trost type reaction, which has also been widely explored. In this mechanism, an electrophilic π-allyl palladium complex reacts with a nucleophile to form an allylic product at the same time as a zerovalent catalyst.…”

Section: Pd-catalyzed Dehydrogenative Coupling Mechanismmentioning

confidence: 99%

“…Specifically, alkenes bearing electron withdrawing groups tend to provide trans β ‐substituted alkenes whereas alkenes with electron donating groups generate α ‐substituted alkenes [63] . In contrast, 1,2‐disubstituted internal alkenes exhibit low reactivity and provide a mixture of regio‐ and stereoisomers because the Mizoroki‐Heck reaction with internal olefins produces a mixture of ( E ) and ( Z )‐products even from a single geometrical isomer [64] …”

Section: General Reaction Mechanism For Aerobic Oxidative Couplingmentioning

confidence: 99%

Synergic Palladium Catalysis for Aerobic Oxidative Coupling

Tabaru

Obora

2022

Eur J Org Chem

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Aerobic oxidative coupling is a dehydrogenative organic transformation in which molecular oxygen acts as a re-oxidant for the catalyst system. Pd has emerged as one of the most popular transition metal catalysts for such reactions. Combinations of Pd with other transition metal catalysts can also provide effective catalytic cycles together with highly atom-and step-economical organic transformations. A synergic Pd catalyst system can promote such reactions with a high degree of efficiency based on a re-oxidation step exhibiting improved kinetics in which two electrons are transferred from another transition metal. This occurs in conjunction with a lower energy barrier than that associated with direct re-oxidation by molecular oxygen. This review highlights recent developments in aerobic oxidative coupling reactions catalyzed by synergic combinations of Pd with other transition metals. Highlighted reactions include dehydrogenative CÀ C bond formation such as arylation of arenes, heteroarenes, alkenes and dehydrogenative CÀ N and CÀ O bond formations with unsaturated hydrocarbons such as alkenes, 1,3-dienes and allenes. Moreover, mechanistic insights into these aerobic reactions based on experimental, computational and optical studies are detailed.

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“…At the time we could not determine conditions to achieve the selective monoarylation reaction of the terminal allylamines, which as mentioned would give rise to the important class of cinnamylamines. In addition, while we had a good handle on the competing mechanisms for the arylation of cinnamylamines to form the 3,3-diarylallylamines, we lacked a similar understanding of how the first arylation occurred – did it also come from a competition between C–H activation (followed by possible isomerization) 15 and γ-selective Mizoroki–Heck coupling, or could the terminal alkene be directly arylated without the involvement of the amine, which under acidic conditions would be protonated. 16 The goal of this work was therefore to determine conditions that would allow us to access cinnamylamines directly, and to address some of the outstanding questions regarding the mechanism of the first arylation.…”

Section: Introductionmentioning

confidence: 99%