Directed, Palladium(II)-Catalyzed Enantioselective anti-Carboboration of Alkenyl Carbonyl Compounds

Liu, Zhen; Li, Xiaohan; Zeng, Tian; Engle, Keary M.

doi:10.26434/chemrxiv.7577597.v1

Cited by 7 publications

(12 citation statements)

References 28 publications

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“…RESULTS AND DISCUSSION Scheme 3 shows the standard reaction conditions identified based on past work. 10,15 Control experiments verified that E/Z isomerization does not occur without the palladium catalyst. Without acetic acid, isomerization is observed at a diminished rate (see SI).…”

Section: Scheme 2: Examples Of Alkene E/z Isomerization Under Non-hydrogenative Conditionsmentioning

confidence: 97%

“…12 This reactivity was then exploited in two stereoconvergent systems. 10,11 No alkene migration was observed despite the use of unactivated alkenes in these reactions, making this an ideal model system for elucidating the mechanistic details of E/Z isomerization. Furthermore, the AQ directing group can stabilize catalytically competent organopalladium complexes, allowing for characterization and in situ monitoring of previously undetectable intermediates by NMR spectroscopy.…”

Section: Scheme 1: Olefin Activation By Pd(ii)mentioning

confidence: 99%

“…Widely accessible alkene feedstocks can thus be converted into value-added isomeric products or into further functionalized target compounds through integration into tandem catalytic processes. [9][10][11] Harnessing the full synthetic potential of these processes, however, hinges on a refined mechanistic understanding, such that they can be controlled and rationally optimized.…”

Section: Introductionmentioning

confidence: 99%

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

Matsuura¹,

Karunananda²,

Liu³

et al. 2020

Preprint

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Pd(II)-catalyzed E/Z isomerization of alkenes is a common process—yet is largely uncharacterized, particularly with non-conjugated alkenes. In this work, the mechanism of Pd(II)-catalyzed E/Z isomerization of unactivated olefins containing an aminoquinoline-based amide directing group is probed using in situ kinetic analysis, spectroscopic studies, kinetic modeling, and DFT calculations. The directing group allows for stabilization and monitoring of previously undetectable intermediates. Collectively, the data are consistent with isomerization occurring through a monometallic nucleopalladation mechanism.

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Section: Scheme 2: Examples Of Alkene E/z Isomerization Under Non-hydrogenative Conditionsmentioning

confidence: 97%

Section: Scheme 1: Olefin Activation By Pd(ii)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Matsuura¹,

Karunananda²,

Liu³

et al. 2020

Preprint

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“…This strategy was further employed for enantioselective difunctionalization of unactivated alkenes. The groups of Engle and Peng, Chen and He reported Pd‐catalyzed substrate‐directed enantioselective anti‐carboboration of alkenes independently. The MOXin ligand was used in Engle's system (Scheme ) while a newly developed MOXca ligand was employed in Peng, Chen and He's system (Scheme ).…”

Section: Substrate Directed Enantioselective Functionalization Of Unamentioning

confidence: 99%

Metal‐Catalyzed Substrate‐Directed Enantioselective Functionalization of Unactivated Alkenes

Wang

Bai

2019

Chin. J. Chem.

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Alkenes are versatile compounds that are available on large scales in industry or through chemical synthesis. Selective functionalization of unactivated alkenes in a chemo‐, regio‐, diastereo‐ and enantioselective fashion is a highly sought‐after goal in organic synthesis. Substrate‐directed enantioselective functionalization of unactivated alkenes provides an important strategy to achieve this goal. Using a functional group on the alkene substrate as a native coordinating group, a two‐point binding mode of the substrate to the metal center enables effective control of regio‐, diastereo‐ and enantioselectivities. Through this strategy, a variety of enantioselective functionalization methods have been developed recently. The recent advances in this area are highlighted here.

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“…While reactions involving removable DGs are intrinsically valuable, they are limited by the fact that the DG needs to be installed and cleaved, requiring a minimum of two concession steps. Additionally, reactions using DGs are difficult to render enantioselective owing to a lack of available coordination sites on the metal for a chiral ligand (14,15).…”

mentioning

confidence: 99%

A Transient Directing Group Strategy Enables Enantioselective Reductive Heck Hydroarylation of Alkenes

Oxtoby¹,

Li²,

Erbay³

et al. 2019

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Metal-coordinating directing groups have seen extensive use in the field of transition-metal-catalyzed alkene functionalization; however, their waste-generating installation and removal steps limit the efficiency and practicality of reactions that rely on their use. Inspired by developments in asymmetric organocatalysis, where reactions rely on reversible covalent interactions between an organic substrate and a chiral mediator, we have developed a transient-directing-group approach to reductive Heck hydroarylation of alkenyl benzaldehyde substrates that proceeds under mild conditions. Highly stereoselective migratory insertion is facilitated by in situ formation of an imine from catalytic amounts of a commercially available amino acid additive. Computational studies reveal an unusual mode of enantioinduction by the remote chiral center in the transient directing group.Among the foremost challenges in modern synthetic chemistry is forming carbon-carbon bonds to establish stereocenters remote from existing functional groups. Catalytic enantioselective alkene functionalization has emerged as an attractive strategy owing to the widespread accessibility and unique reactivity profile of alkenes. Within the contemporary alkene functionalization toolkit, palladium-catalyzed Heck-type arylations [1] constitute an especially powerful mode of reactivity as a result of their broad substrate scope and functional-group compatibility. Nevertheless, significant limitations in Heck-type chemistry remain, including controlling regioselectivity with multi-substituted, electronically neutral alkenes; suppressing b-hydride elimination to enable interception with additional reaction partners; and achieving stereoinduction during intermolecular migratory insertion. [2] The use of directing groups (DGs), functional motifs containing one or more binding sites that are capable of facilitating efficient intramolecular delivery of a reagent or catalyst, is a classical strategy in organic synthesis for controlling reactivity and selectivity. [3] In recent years, remov-able-DG strategies have been successfully applied to various alkene functionalization reactions, [4] including classical Mizoroki-Heck alkene arylations. [5] In the realm of difunctionalization and hydrofunctionalization of acyclic internal alkenes, removable bidentate DGs, such as 8-aminoquinoline-derived amides, have proven especially valuable due to their ability to suppress b-hydride elimination and allow subsequent transmetalation/ligand exchange. [6,7] While reactions involving removable DGs are intrinsically valuable, they are limited by the fact that the DG needs to be installed and cleaved, requiring a minimum of two concession steps (Scheme 1 A). Additionally, reactions using DGs are difficult to render enantioselective owing to a lack of available coordination sites on the metal for a chiral ligand. [8] Developing a strategy whereby a chiral directing moiety could condense with the substrate reversibly, promote the desired reaction, and then dissociate effectiv...

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Directed, Palladium(II)-Catalyzed Enantioselective anti-Carboboration of Alkenyl Carbonyl Compounds

Cited by 7 publications

References 28 publications

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

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

Metal‐Catalyzed Substrate‐Directed Enantioselective Functionalization of Unactivated Alkenes

A Transient Directing Group Strategy Enables Enantioselective Reductive Heck Hydroarylation of Alkenes

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