A Strategy for Selective Catalytic B–H Functionalization of o-Carboranes

Accounts of Chemical Research, Год журнала: 2021, Номер 54(21), С. 4065 - 4079

Опубликована: Окт. 24, 2021

ConspectusCarboranes are a class of polyhedral carbon-boron molecular clusters featuring three-dimensional aromaticity, which often considered as 3D analogues benzene. Their unique structural and electronic properties make them invaluable building blocks for applications ranging from functional materials to versatile ligands pharmaceuticals. Thus, selective functionalization carboranes has received tremendous research interest. In earlier days, the vast majority works in this area were focused on cage carbon via facile deprotonation CH, followed by reaction with electrophiles. On contrary, B-H activation is very challenging since 10 bonds o-carborane similar, how achieve desired transformation at specific boron vertex long-standing issue.As more electronegative than boron, property results different charges cage, follow order B(3,6)-H ≪ B(4,5,7,11)-H < B(8,10)-H B(9,12)-H. We thought that difference may trigger favorite interaction proper transition metal complex bond carborane, could be utilized solve selectivity issue. Accordingly, our strategy described follows: (1) electron-rich catalysts good most electron-deficient (connected both C-H vertices); (2) relatively B(8,9,10,12)-H (with no bonding either (3) directing-group-assisted catalysis appropriate only one vertex), whose lie middle range bonds. This been successfully applied laboratory other groups development series synthetic routes catalytic carborane resulting synthesis large number cage-boron-functionalized derivatives regioselective fashion. Subsequently, significant progress emerging made.In 2013 we reported tetrafluorination o-carboranes using an Pd(II) salt, [Pd(MeCN)4][BF4], catalyst. 2014 disclosed first example carboxy-directed alkenylation B(4) promoted Ir(III) 2017 presented Ir(I)-catalyzed diborylation also uncovered Pd-catalyzed asymmetric chiral-at-cage 2018. These proof-of-principle studies have greatly stimulated activities enabled catalysts. so far developed toolbox methods B-olefination, -arylation, -alkenylation, -alkynylation, -oxygenation, -sulfenylation, -borylation, -halogenation, -amination. recently expanded base catalysis. As field progresses, expect will invented, detailed Account promote these efforts.

Язык: Английский

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Recent Advances in Transition Metal-Catalyzed Selective B-H Functionalization ofo-Carboranes

Bulletin of the Chemical Society of Japan, Год журнала: 2020, Номер 94(3), С. 879 - 899

Опубликована: Дек. 18, 2020

Abstract Carboranes are a class of carbon-boron molecular clusters, possessing extraordinary characteristics including three-dimensional aromaticity conjugated by σ-bonds, icosahedral geometry and inherent robustness. They finding growing applications as valuable building blocks in boron neutron capture therapy agents, pharmacophores, nanomaterials, optoelectronic, organometallic/coordination chemistry more. Therefore, the effective controlled functionalization carboranes has attracted enormous research interests, particularly regio- enantio-selective cage BH derivatization among ten chemically similar vertices o-carboranes. Only recent few years, significant progress been made transition metal catalyzed vertex-specific functionalization. This review summarizes advances this realm.

Язык: Английский

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Organocatalytic Asymmetric Synthesis of o-Carboranyl Amines

Journal of the American Chemical Society, Год журнала: 2025, Номер unknown

Опубликована: Янв. 14, 2025

Carboranyl amines are distinct from typical organic amines. Due to the electronic influence of carborane cage, they have low nucleophilicity and reluctant alkylate. Moreover, asymmetric synthesis chiral carboranes is still in its infancy. Herein we achieved first catalytic N-alkylation o-carboranyl amine, providing general access diverse secondary with high efficiency enantioselectivity under mild conditions. For time, organocatalysis was introduced chemistry. Key success use situ generated (naphtho-)quinone methides as alkylating reagents suitable acid catalysts. This protocol also applicable S-alkylation 1-SH-o-C2B10H11. Control experiments kinetic studies provided important insights into reaction mechanism, which likely involves rate-determining generation quinone methide followed by fast enantio-determining nucleophilic addition.

Язык: Английский

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Iridium-Catalyzed Cyclative Indenylation and Dienylation through Sequential B(4)–C Bond Formation, Cyclization, and Elimination from o-Carboranes and Propargyl Alcohols

Journal of the American Chemical Society, Год журнала: 2020, Номер 142(22), С. 9890 - 9895

Опубликована: Май 12, 2020

Described herein is the first iridium-catalyzed cyclative indenylation through sequential B(4)–C and intramolecular C–C bond formation from o-carboranes propargyl alcohols, leading to of B(4)-indenylated with excellent regioselectivity via direct B–H activation. Moreover, regioselective 1,3-dienylation has been accessed activation, dehydration, decarboxylation, producing B(4)-dienylated o-carboranes.

Язык: Английский

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Copper-Catalyzed Electrochemical Selective B–H Oxygenation of o-Carboranes at Room Temperature

Journal of the American Chemical Society, Год журнала: 2020, Номер 142(15), С. 6940 - 6945

Опубликована: Март 31, 2020

Copper-catalyzed electrochemical selective cage B–H oxygenation of o-carboranes has been achieved for the first time. Under a constant electric current (4.0 mA) at room temperature, copper-catalyzed cross-coupling carboranyl amides with lithium phenolates results in formation B(4,5)-diphenolated via direct activation, whereas use tert-butoxide affords B(4)-monooxygenated products. This reaction does not require any additional chemical oxidants and generates H2 salt as byproducts. Control experiments indicated that high-valent Cu(III) species is likely involved process.

Язык: Английский

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Pd‐Catalyzed Selective Bifunctionalization of 3‐Iodo‐o‐Carborane by Pd Migration

Angewandte Chemie International Edition, Год журнала: 2019, Номер 59(12), С. 4851 - 4855

Опубликована: Дек. 25, 2019

Abstract A palladium‐catalyzed highly selective 3,4‐bifunctionalization of 3‐I‐ o ‐carborane has been developed, leading to the preparation 3‐alkenyl‐4‐R‐ ‐carboranes (R=alkyl, alkynyl, aryl, allyl, CN, and amido) in high excellent yields. This protocol combines sequential activation cage B(3)−I B(4)−H bonds by Pd migration from exo ‐alkenyl sp 2 C B(4), which is driven thermodynamic force. represents a brand‐new strategy for bifunctionalization carboranes with two different substituents.

Язык: Английский

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Regioselective B(3,4)–H arylation of o-carboranes by weak amide coordination at room temperature

Chemical Science, Год журнала: 2020, Номер 11(39), С. 10764 - 10769

Опубликована: Янв. 1, 2020

B–H: site-selective B(3,4)–H arylations were accomplished at room temperature by versatile palladium catalysis enabled weakly coordinating amides.

Язык: Английский

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Ir-Catalyzed Selective B(3)-H Amination of o-Carboranes with NH₃

Journal of the American Chemical Society, Год журнала: 2021, Номер 143(11), С. 4148 - 4153

Опубликована: Март 15, 2021

Ammonia gas, NH3, is a cheap and widely used industrial feedstock, which has received tremendous research interests in its functionalization. This work reports breakthrough catalytic selective cage B(3)-H amination of o-carboranes with NH3 via Ir-catalyzed B-H/N-H dehydrocoupling, offering convenient efficient access to series 3-NH2-o-carborane derivatives moderate high isolated yields broad substrate scope. The employment readily available gas as the aminating reagent H2 sole byproduct endows protocol economy, practicability, environmental friendliness. A plausible reaction mechanism proposed on basis control experiments.

Язык: Английский

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Electrochemical Cage Activation of Carboranes

Angewandte Chemie International Edition, Год журнала: 2022, Номер 61(20)

Опубликована: Фев. 11, 2022

Abstract Carboranes are boron–carbon molecular clusters that possess unique properties, such as their icosahedron geometry, high boron content, and delocalized three‐dimensional aromaticity. These features render carboranes valuable building blocks for applications in supramolecular design, nanomaterials, optoelectronics, organometallic coordination chemistry, neutron capture therapy (BNCT) agents. Despite tremendous progress this field, stoichiometric chemical redox reagents largely required the oxidative activation of carborane cages. In context, electrosyntheses represent an alternative strategy more sustainable syntheses. It is only recent few years considerable has been made electrochemical cage functionalization carboranes, which summarized Minireview. We anticipate electrocatalysis will serve increasingly powerful stimulus within current renaissance electrochemistry.

Язык: Английский

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A variable bidentate traceless directing group for nickel-catalyzed regioselective B–H poly-chalcogenation of o-carboranes

Inorganic Chemistry Frontiers, Год журнала: 2025, Номер unknown

Опубликована: Янв. 1, 2025

A nickel-catalyzed direct cage B–H poly-chalcogenation of icosahedral carborane clusters, enabled by a variable bidentate 8-aminoquinoline traceless directing group, has been developed under oxidant-free and weakly basic conditions.

Язык: Английский

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