Asymmetric intermolecular allylic C–H amination of alkenes with aliphatic amines

Science, Journal Year: 2022, Volume and Issue: 378(6625), P. 1207 - 1213

Published: Dec. 15, 2022

Aliphatic allylic amines are found in a great variety of complex and biorelevant molecules. The direct C-H amination alkenes serves as the most straightforward method toward these motifs. However, use widely available internal with aliphatic this transformation remains synthetic challenge. In particular, palladium catalysis faces twin challenges inefficient coordination Pd(II) to but excessively tight therefore inhibitory by basic amines. We report general solution problems. developed protocol, contrast classical Pd(II/0) scenario, operates through blue light-induced Pd(0/I/II) manifold mild aryl bromide oxidant. This open-shell approach also enables enantio- diastereoselective amination.

Language: Английский

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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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Thioether-Directed NiH-Catalyzed Remote γ-C(sp³)–H Hydroamidation of Alkenes by 1,4,2-Dioxazol-5-ones

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(37), P. 14962 - 14968

Published: Sept. 8, 2021

A NiH-catalyzed thioether-directed cyclometalation strategy is developed to enable remote methylene C–H bond amidation of unactivated alkenes. Due the preference for five-membered nickelacycle formation, chain-walking isomerization initiated by NiH insertion an alkene can be terminated at γ-methylene site from moiety. By employing 2,9-dibutyl-1,10-phenanthroline (L4) as ligand and dioxazolones reagent, occurs γ-C(sp3)–H bonds afford amide products in up 90% yield (>40 examples) with remarkable regioselectivity (up 24:1 rr).

Language: Английский

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Tunable and Switchable Catalysis Enabled by Cation-Controlled Gating with Crown Ether Ligands

Accounts of Chemical Research, Journal Year: 2023, Volume and Issue: 56(8), P. 971 - 981

Published: March 28, 2023

ConspectusCatalysis has become an essential tool in science and technology, impacting the discovery of pharmaceuticals, manufacture commodity chemicals plastics, production fuels, much more. In most cases, a particular catalyst is optimized to mediate reaction, continually producing desired product at given rate. There enormous opportunity developing catalysts that are dynamic, capable responding change environment alter structure function. Controlled catalysis, which activity or selectivity catalytic reaction can be adjusted through external stimulus, offers opportunities for innovation catalysis. Catalyst could simplified if single thoughtfully designed complex work synergistically with additives optimize performance rather than trying multitude different metal/ligand combinations. Temporal control gained facilitate execution multiple reactions same flask, example, by activating one deactivating another avoid incompatibilities. Selectivity switching enable copolymer synthesis well-defined chemical material properties. These applications might sound futuristic synthetic catalysts, but nature, such degree controlled catalysis commonplace. For allosteric interactions and/or feedback loops modulate enzymatic small-molecule sequence-defined polymerization mixtures containing many sites. regulation achieved "gating" substrate access active site. Fundamental advances design needed better understand factors arena chemistry, particularly achieving gating outside macromolecular environments. this Account, development principles cation-controlled described. The guiding hypothesis was site controlling dynamics hemilabile ligand secondary Lewis acid/base cation-dipole interactions. To enforce interactions, sitting interface organometallic supramolecular chemistry were designed. A macrocyclic crown ether incorporated into robust pincer ligand, these "pincer-crown ether" ligands have been explored Complementary studies detailed mechanistic analysis guided iridium, nickel, palladium pincer-crown gating. Toggling gate between open closed states leads switchable where cation addition/removal changes turnover frequency selectivity. Varying tunable tuned based on identity amount salt added. Research focused alkenes, isomerization reactions, turn led catalysts.

Language: Английский

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Stereodivergent, Kinetically Controlled Isomerization of Terminal Alkenes via Nickel Catalysis

Angewandte Chemie International Edition, Journal Year: 2024, Volume and Issue: 63(21)

Published: March 18, 2024

Abstract Because internal alkenes are more challenging synthetic targets than terminal alkenes, metal‐catalyzed olefin mono‐transposition (i.e., positional isomerization) approaches have emerged to afford valuable E ‐ or Z‐ from their complementary alkene feedstocks. However, the applicability of these methods has been hampered by lack generality, commercial availability precatalysts, and scalability. Here, we report a nickel‐catalyzed platform for stereodivergent / Z ‐selective synthesis at room temperature. Commercial reagents enable this one‐carbon transposition ‐internal via Ni−H‐mediated insertion/elimination mechanism. Though mechanistic regime is same in both systems, underlying pathways that lead each active catalysts distinct, with catalyst forming comproportionation an oxidative addition complex followed substrate protonation metal trialkylphosphonium salt additive. In case, ligand sterics denticity control stereochemistry prevent over‐isomerization.

Language: Английский

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Selecting Double Bond Positions with a Single Cation-Responsive Iridium Olefin Isomerization Catalyst

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(7), P. 2792 - 2800

Published: Feb. 8, 2021

The catalytic transposition of double bonds holds promise as an ideal route to alkenes value fragrances, commodity chemicals, and pharmaceuticals; yet, selective access specific isomers is a challenge, normally requiring independent development different catalysts for products. In this work, single cation-responsive iridium catalyst selectively produces either two internal alkene isomers. the absence salts, positional isomerization 1-butene derivatives furnishes 2-alkenes with exceptional regioselectivity stereoselectivity. same catalyst, in presence Na+, mediates isomerizations produce 3-alkenes. synthesis new pincer-crown ether based on aza-18-crown-6 proved instrumental achieving cation-controlled selectivity. Experimental computational studies guided mechanistic model that explains observed selectivity various functionalized 1-butenes, providing insight into strategies noncovalent modifications.

Language: Английский

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Highly Z-Selective Double Bond Transposition in Simple Alkenes and Allylarenes through a Spin-Accelerated Allyl Mechanism

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(8), P. 3070 - 3074

Published: Feb. 17, 2021

Double-bond transposition in alkenes (isomerization) offers opportunities for the synthesis of bioactive molecules, but requires high selectivity to avoid mixtures products. Generation Z-alkenes, which are present many natural products and pharmaceuticals, is particularly challenging because it usually less thermodynamically favorable than generation E isomers. We report a β-dialdiminate-supported, high-spin cobalt(I) complex that can convert terminal alkenes, including previously recalcitrant allylbenzenes, Z-2-alkenes with unprecedentedly regioselectivity stereoselectivity. Deuterium labeling studies indicate catalyst operates through π-allyl mechanism, different from alkyl mechanism followed by other Z-selective catalysts. Computations triplet alkene undergoes spin state change resting-state singlet lowest-energy C–H activation transition state, leads Z product. This suggests this enables differentiate stereodefining barriers system, more generally spin-state changes may offer route toward novel stereocontrol methods first-row metals.

Language: Английский

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Olefin functionalization/isomerization enables stereoselective alkene synthesis

Nature Catalysis, Journal Year: 2021, Volume and Issue: 4(8), P. 674 - 683

Published: July 29, 2021

Language: Английский

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Cobalt-Catalyzed Desymmetric Isomerization of Exocyclic Olefins

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(49), P. 20633 - 20639

Published: Dec. 6, 2021

Chiral cyclic olefins, 1-methylcyclohexenes, are versatile building blocks for the synthesis of pharmaceuticals and natural products. Despite prevalence these structural motifs, development efficient synthetic methods remains an unmet challenge. Herein we report a novel desymmetric isomerization exocyclic olefins using series newly designed chiral cobalt catalysts, which enables straightforward construction 1-methylcyclohexenes with diversified functionalities. The utility this methodology is highlighted by concise enantioselective product, β-bisabolene. versatility reaction products further demonstrated multifarious derivatizations.

Language: Английский

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Part per million levels of an anionic iron hydride complex catalyzes selective alkene isomerization via two-state reactivity

Chem Catalysis, Journal Year: 2021, Volume and Issue: 1(3), P. 631 - 647

Published: June 7, 2021

Language: Английский

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