Anti-Markovnikov hydroallylation reaction of alkenes via scandium-catalyzed allylic C‒H activation

Nature Communications, Journal Year: 2025, Volume and Issue: 16(1)

Published: Feb. 6, 2025

Compared with rare-earth (RE)…heteroatom interaction, RE…π frequently used in facilitating regio- and stereoselectivity of olefin polymerizations, is seldomly to trigger catalytic C - H functionalization. Here, we describe a direct anti-Markovnikov hydroallylation reaction styrene derivatives 1-aryl-2-alkyl alkenes α-alkenes by use interaction. This protocol provides straightforward atom-efficient route for the synthesis valuable chain elongated internal (65 examples, up 99% yield, > 19:1 E/Z ratio). The proceeds via an allylic Csp3‒H activation pathway initiated site-selective deprotonation assistance cationic imidazolin-2-iminato scandium alkyl species followed alkene insertion into resulting scandium-allyl bond. A amount Lewis base additives, such as amine tetrahydrofuran (THF) show significant effects on reactivity selectivity. mechanism elucidated experimental studies theoretical calculations.

Language: Английский

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Synthesis of Rigid Stepladder Polymers via Scandium-Catalyzed Polyspiroannulation of Quinoline with Alkyne

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 1, 2025

Polymers with rigid three-dimensional architectures have attracted significant attention due to their high rigidity and intrinsic microporosity. Here, we report the synthesis of a new class stepladder polymers featuring unique spirodihydroquinoline skeletons. Under catalysis half-sandwich scandium catalyst, quinoline compounds bearing both an aryl substituent (e.g., phenyl or naphthyl) alkynyl group C≡CSiMe3) selectively undergo dearomative polyspiroannulation between skeleton alkyne unit via ortho-C–H activation group. This reaction efficiently yields comprising quaternary carbon stereocenter unprotected N–H Treatment N–H-containing alkyl lithium reagent followed by methyl iodide leads quantitative formation corresponding N-methylated polymers, which exhibit enhanced thermal stability porosity compared counterparts.

Language: Английский

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Theoretical Insights into Rare-Earth-Catalyst-Controlled Diastereo- and Enantioselective [3 + 2] Annulation of Aromatic Aldimines with Styrenes

Inorganic Chemistry, Journal Year: 2025, Volume and Issue: unknown

Published: Feb. 5, 2025

Rare-earth-catalyzed annulation reactions using alkenes via C–H activation offer an atom-efficient approach to constructing cyclic compounds. However, the mechanisms underlying these remain poorly understood, limiting rational design of related catalytic systems. Recently, Hou and Cong reported unprecedented example rare-earth-catalyst-controlled diastereodivergent asymmetric [3 + 2] aromatic aldimines with alkenes. To elucidate origins diastereo- enantioselectivity, density functional theory calculations were performed. The results revealed that styrene insertion step determines stereoselectivity. Styrene follows a similar metal–styrene interaction pattern across different catalysts. Specifically, during cis-insertion, interacts strongly metal center, exhibiting significant Sc···Ph interactions, whereas such interactions are absent trans-insertion. Thus, when catalyst is employed small ligand, stereoselectivity primarily governed by electronic factors, favoring cis-insertion mode. In contrast, for more sterically hindered catalyst, in insufficient overcome steric effects, leading preference trans-insertion mode, which minimizes hindrance. These findings deeper insights into catalyst-controlled enantioselectivity will also contribute stereospecific rare-earth catalysis.

Language: Английский

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Regio- and Stereoselective Hydroalkynylation of Internal Alkynes with Terminal Alkynes by Half-Sandwich Rare-Earth Catalysts

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: Feb. 5, 2025

The regio- and stereoselective hydroalkynylation of internal alkynes with terminal is great interest importance as a straightforward route for synthesizing multisubstituted 1,3-enynes. However, this transformation often suffers from stereoselectivity issues when working unsymmetrical alkynes. Herein, we report the first time syn-stereoselective variety heteroatom-functionalized including homopropargyl ethers, thioethers, tertiary amines by half-sandwich rare-earth catalysts. This protocol provides an atom-efficient synthesis new family heteroatom (O, S, or N)-functionalized 1,3-enynes, featuring 100% atom-efficiency, broad substrate scope, high syn-stereoselectivity (>19:1 r.r. >19:1 syn/anti). mechanistic details have been elucidated deuterium-labeling experiments, control isolation transformations key reaction intermediates, revealing that proceeded through C(sp)–H deprotonation alkyne scandium alkyl species to form catalytically active dimeric tetraalkynyl followed heteroatom-assisted insertion into Sc–alkynyl bond subsequent protonolysis resulting Sc–alkenyl another molecule. coordination N) catalyst metal center plays critically important role in achieving level reactivity stereoselectivity. Remarkably, can be recovered reused, constituting example recyclable system

Language: Английский

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Mechanisms and Origins of Regioselectivity in Rare-Earth-Catalyzed C–H Functionalization of Anisoles and Thioanisoles

Inorganic Chemistry, Journal Year: 2025, Volume and Issue: unknown

Published: March 12, 2025

The direct catalytic C–H functionalization of aromatic compounds such as anisoles and thioanisoles is great interest significance. However, achieving precise regioselectivity remains a major challenge. In this study, we conducted comprehensive density functional theory calculations to explore the mechanisms rare-earth-catalyzed regioselective alkylation, borylation, silylation anisole thioanisole. results reveal that in cationic alkylation systems, alkene insertion step follows substrate-assisted mechanism, which an additional substrate molecule acts ligand facilitate transformation. neutral borylation although mononuclear hydride species readily dimerize into binuclear due thermodynamic stability, process predominantly proceeds via pathway. Furthermore, origins were thoroughly elucidated. A detailed analysis electronic steric effects related transition states reveals that, for anisole, primarily governed by ring strain. Since α-C(sp3)–H activation involves formation highly strained three-membered ring, reaction preferentially occurs at ortho-C(sp2)–H site, forming less four-membered ring. contrast, thioanisole, play decisive role, driving more negatively charged α-C(sp3) site stronger metal–carbon interactions.

Language: Английский

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Overlooked Ligand Role of Pyridine Substrate in Site Selectivity of Rare-Earth-Catalyzed C–H Alkylation with Alkenes

Inorganic Chemistry, Journal Year: 2025, Volume and Issue: unknown

Published: April 11, 2025

The rare-earth-catalyzed C-H alkylation of heteroatom-containing substrates with alkenes has been extensively studied over the past decade. Traditionally, those have regarded primarily as reactants in these reactions. In this study, mechanism 2-ethylpyridine styrene was investigated by DFT calculations, revealing often-overlooked ligand effect pyridine substrates. Our findings demonstrate that substrates, acting ligands, play a pivotal role modulating site selectivity during activation. These results enhance our understanding rare-earth catalysis and provide valuable insights into its versatile reactivity, offering novel perspective on dual roles (both reactant ligand) which are widely used functionalization

Language: Английский

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Proton-Modulated Nickel Hydride Electrocatalysis for the Hydrogenation of Unsaturated Bonds and Olefin Isomerization

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: April 21, 2025

Transition-metal hydrides stand as indispensable intermediates in both energy conversion and organic synthesis. Their electrochemical generation represents a compelling sustainable approach, enabling precise control over the reactivity expanding scope of electrocatalytic hydrogenation isomerization. However, major challenge Ni-catalyzed is competing hydrogen evolution reaction (HER), which has led to various innovative strategies aimed at circumventing Ni-H formation. Here, we pursued an alternative approach by designing bifunctional ligand with pendant amine moiety promote This design enabled selective (semi)hydrogenation diverse range substrates, including terminal internal alkynes, alkenes, aldehydes, achieving unprecedented substrate scope. Remarkably, also demonstrated tunable positional selectivity for olefin isomerization employing different types proton sources. Our method exhibits excellent functional group tolerance, streamlining access pharmaceuticals their derivatives. Computational studies revealed crucial, noninnocent role source modulating metal hydride selectivity, either through bonding, direct protonation amine, or facilitation protodemetalation.

Language: Английский

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NHC-Catalyzed and Brønsted Acid Copromoted E → Z Isomerization Mode of Breslow Intermediates Leading to Ralfuranones

Organic Letters, Journal Year: 2025, Volume and Issue: unknown

Published: May 12, 2025

Different Z/E-isomers of functional molecules display distinct chemical and biological activities. The E → Z isomerization reaction is a contra-thermodynamic direction presents long-standing challenge in synthetic transformation. To date, organic catalysis methods for manipulating E/Z are still under development. Here we show new N-heterocyclic carbene (NHC)-catalyzed mode. E-isomer enedial undergoes to give Z-isomer Breslow intermediate via NHC catalysis, an intramolecular hydrogen bond can greatly stabilize this conformation. Subsequently, the Brønsted acid promotes further redox-neutral reaction. desired ralfuranone products obtained from our method be readily transformed various molecules.

Language: Английский

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Asymmetric Bimetallic Catalysis Enabled Alkenyl Z/E Mutual Isomerization

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: June 5, 2025

Olefins are fundamental functional groups present in numerous molecules, and the geometrical configuration of C═C bonds often plays a critical role determining properties these compounds. Alkenyl isomerization is, principle, one most efficient approaches for accessing stereodefined olefins. While some progress has been made achieving unidirectional Z → E or conversion via olefin isomerization, there remains strong demand controllable, bidirectional bonds. Herein, we method Z/E mutual alkenyl by using Pd/Cu catalytic system. This process involves Pd-mediated π-σ-π interconversion followed selective trapping π-allyl-Pd intermediates with N-metalated azomethine ylides generated chiral Cu-catalyst. The reaction enables synthesis non-natural amino acid derivatives bearing Z- E-alkenyl an enantio- Z/E-divergent manner, yields up to 92%, > 20:1 E/Z, >99% ee. Furthermore, is scalable gram quantities, resulting products can be transformed into valuable molecules adorned groups. Computational studies show that bimetallic system better distinguishes among eight stereoisomers than monometallic system, which results exceptional Z/E-selectivity products. offers robust protocol synthesizing E-trisubstituted olefins motif utilizing readily available Z/E-mixture substrates.

Language: Английский

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