Construction of Complex Cyclobutane Building Blocks by Photosensitized [2 + 2] Cycloaddition of Vinyl Boronate Esters

Organic Letters, Год журнала: 2021, Номер 23(9), С. 3496 - 3501

Опубликована: Апрель 12, 2021

Cyclobutyl moieties in drug molecules are rare, and general, they minimally substituted stereochemically simple. Methods to assemble structurally complex cyclobutane building blocks suitable for rapid diversification thus highly desirable. We report herein a photosensitized [2 + 2] cycloaddition with vinyl boronate esters affording straightforward access complex, densely functionalized scaffolds. Mechanistic studies suggest an activation mode involving energy transfer the styrenyl alkene rather than ester.

Язык: Английский

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Direct Light‐Enabled Access to α‐Boryl Radicals: Application in the Stereodivergent Synthesis of Allyl Boronic Esters**

Angewandte Chemie International Edition, Год журнала: 2023, Номер 62(34)

Опубликована: Июнь 16, 2023

Abstract Operationally simple strategies to assemble boron containing organic frameworks are highly enabling in synthesis. While conventional retrosynthetic logic has engendered many platforms focusing on the direct formation of C−B bonds, α‐boryl radicals have recently reemerged as versatile open‐shell alternatives access organoborons via adjacent C−C bond formation. Direct light‐enabled α‐activation is currently contingent photo‐ or transition metal‐catalysis activation efficiently generate radical species. Here, we disclose a facile α‐halo boronic esters using only visible light and Lewis base enable homolytic scission. Intermolecular addition styrenes facilitates rapid construction E ‐allylic esters. The simplicity permits strategic merger this construct with selective energy transfer catalysis complimentary stereodivergent synthesis Z

Язык: Английский

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Direct Alkylation of Glycine Derivatives via Photoinduced Palladium Catalysis, Utilizing Intermolecular Hydrogen Atom Transfer Mediated by Alkyl Radicals

ACS Catalysis, Год журнала: 2023, Номер 13(24), С. 15652 - 15662

Опубликована: Ноя. 21, 2023

Unveiling the alkyl/Pd hybrid species is a unique sp3-C-centered radical for facilitating intermolecular hydrogen atom transfer (HAT) in development of direct alkylation glycine derivatives. This transformative reaction proceeds smoothly under simple and mild conditions, exhibiting impressive versatility terms substrate scope encompassing both derivatives alkyl bromides while showcasing remarkable tolerance toward diverse functional groups. To shed light on underlying mechanism, extensive investigations involving control experiments, deuterium labeling, clocking, kinetic studies have been conducted. The collected data consistently support pathway formation Pd(I)/alkyl followed by HAT elimination steps that lead to situ imine intermediates, ultimately culminating final stage through addition.

Язык: Английский

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Direct C(sp3)-H functionalization with aryl and alkyl radicals as intermolecular hydrogen atom transfer (HAT) agents

Chemical Communications, Год журнала: 2024, Номер unknown

Опубликована: Янв. 1, 2024

Recent years have witnessed the emergence of direct intermolecular C(sp

Язык: Английский

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Photochemical Radical C–H Halogenation of Benzyl N‐Methyliminodiacetyl (MIDA) Boronates: Synthesis of α‐Functionalized Alkyl Boronates

Angewandte Chemie International Edition, Год журнала: 2020, Номер 60(7), С. 3454 - 3458

Опубликована: Окт. 20, 2020

Abstract α‐Haloboronates are useful organic synthons that can be converted to a diverse array of α‐substituted alkyl borons. Methods α‐haloboronates limiting and often suffer from harsh reaction conditions. Reported herein is photochemical radical C‐H halogenation benzyl N ‐methyliminodiacetyl (MIDA) boronates. Fluorination, chlorination, bromination reactions were effective by using this protocol. Upon with different nucleophiles, the C−Br bond in brominated product could readily transformed series C−C, C−O, C−N, C−S, C−P, C−I bonds, some which difficult forge α‐halo sp 2 ‐B boronate esters. An activation effect B(MIDA) moiety was found.

Язык: Английский

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Transition metal-free synthesis of alkyl pinacol boronates

Organic & Biomolecular Chemistry, Год журнала: 2020, Номер 18(44), С. 8939 - 8974

Опубликована: Янв. 1, 2020

This review systematically outlined the research in area of transition metal free synthesis alkyl pinacol boronates, which are versatile and important scaffolds to construct diverse organic compounds.

Язык: Английский

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Photoredox‐Mediated Reaction of gem‐Diborylalkenes: Reactivity Toward Diverse 1,1‐Bisborylalkanes

Chemistry - A European Journal, Год журнала: 2020, Номер 26(24), С. 5360 - 5364

Опубликована: Март 6, 2020

Abstract The use of gem ‐diborylalkenes as radical‐reactive groups is explored for the first time. These reactions provide an efficient and general method photochemical conversion to rapidly access 1,1‐bisborylalkanes. This exploits a novel photoredox decarboxylative radical addition afford α‐ ‐diboryl carbon‐centered radicals, which benefit from additional stability by virtue interaction with empty p‐orbitals on borons. reaction offers highly modular regioselective approach γ‐amino ‐diborylalkanes. Furthermore, EPR spectroscopy DFT calculations have provided insight into mechanism underlying photochemistry bis‐metalated respectively.

Язык: Английский

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Recent Advances in Asymmetric Transformations of Unactivated Alkanes and Cycloalkanes through Direct C—H Functionalization

Chinese Journal of Chemistry, Год журнала: 2022, Номер 40(23), С. 2825 - 2837

Опубликована: Авг. 17, 2022

Comprehensive Summary The direct conversion of unactivated alkanes and cycloalkanes into structurally diverse molecules through aliphatic C—H functionalization is a useful process, which has attracted intense interest from academia industry. Methods to control chemo‐ site‐selectivity, combined with asymmetric catalysis, provide appealing access high value‐added enantiomer‐enriched compounds but are far less developed. This review focuses on recent progress in ( i ) reactions or prochiral substrates generate stereocenter adjacent the cleaved C(sp 3 )–H bond, ii enantiodiscriminatory creating new stereogenic center carbon bond. Elegant strategies discussed, including metal carbene‐induced insertions by chiral rhodium catalysts, b metal‐ oxo ‐mediated oxidation biomimetic manganese c enzyme catalysis cytochromes P450 variants, d dual photocatalyst Lewis acid (CLA) phosphoric (CPA). These catalytic systems can not only precisely recognize primary, secondary tertiary bonds at specific positions cycloalkanes, also support level stereoselectivity reactions. It expected that advances will stimulate further synthetic methodology, pharmaceutical development industrial processes.

Язык: Английский

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1,2‐Boryl Migration Enables Efficient Access to Versatile Functionalized Boronates

European Journal of Organic Chemistry, Год журнала: 2022, Номер 2022(9)

Опубликована: Янв. 12, 2022

Abstract Organoboronates are synthetically useful and highly valuable building blocks in synthetic medicinal chemistry. Two‐electron reactions allow for the rapid construction of organoboronates via nucleophilic 1,2‐boron shift boron ate complexes or MIDA‐mediated 1,2‐boryl migration. Radical approaches through neutral boronic esters have been demonstrated to be feasible, providing complementary methods access these privileged scaffolds. In this Review, recent achievements highlighted future opportunities discussed, with an emphasis on different operative modes catalysis reaction pathways.

Язык: Английский

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Radical Aryl Migration from Boron to Carbon

Journal of the American Chemical Society, Год журнала: 2021, Номер 143(25), С. 9320 - 9326

Опубликована: Июнь 20, 2021

Radical aryl migration reactions represent a unique type of organic transformations that involve the intramolecular an group from carbon or heteroatom to C- heteroatom-centered radical through spirocyclic intermediate. Various elements, including N, O, Si, P, S, Sn, Ge, and Se, have been reported participate in migrations. However, boron center has not date. In this communication, 1,5-aryl boronate complexes is presented. C-radicals readily generated addition onto alkenyl are shown engage provide 4-aryl-alkylboronic esters. As can be situ by reaction alkenylboronic acid esters with lithium reagents, moiety varied, providing access series arylated products starting same ester via divergent chemistry. Reactions proceed high diastereoselectivity under mild conditions, also analogous 1,4-aryl shifts feasible. The suggested mechanism supported DFT calculations.

Язык: Английский

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