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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Carboranes as unique pharmacophores in antitumor medicinal chemistry

Molecular Therapy — Oncolytics, Год журнала: 2022, Номер 24, С. 400 - 416

Опубликована: Янв. 10, 2022

Carborane is a carbon-boron molecular cluster that can be viewed as 3D analog of benzene. It features special physical and chemical properties, thus has the potential to serve new type pharmacophore for drug design discovery. Based on relative positions two cage carbons, icosahedral closo-carboranes classified into three isomers, ortho-carborane (o-carborane, 1,2-C2B10H12), meta-carborane (m-carborane, 1,7-C2B10H12), para-carborane (p-carborane, 1,12-C2B10H12), all them deboronated generate their nido- forms. Cage compound carborane its derivatives have been demonstrated useful entities in antitumor medicinal chemistry. The applications carboranes field research mainly include boron neutron capture therapy (BNCT), BNCT/photodynamic dual sensitizers, anticancer ligands. This review summarizes progress achieved up October 2021, with particular emphasis signaling transduction pathways, structures, mechanistic considerations using carboranes.

Язык: Английский

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“Cage Walking” Synthetic Strategy for Unusual Unsymmetrical Supramolecular Cages

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(15), С. 8569 - 8575

Опубликована: Апрель 6, 2023

Developing novel assembly methods for supramolecular compounds has long been a research challenge. Herein, we describe how to integrate the B-C coupling reaction and "cage walking" process into coordination self-assembly construct cages. In this strategy, dipyridine linkers containing alkynes react with metallized carborane backbone through then resulting in metallacages. However, without alkynyl groups can form only metallacycles. We regulate size of metallacages based on length bipyridine linkers. When tridentate-pyridine participate reaction, new type ravel is formed. The metallization carboranes, especially cages play vital role reaction. This work provides promising principle synthesis opens up opportunity field.

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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Steric-Effects-Directed B–H Bond Activation of para-Carboranes

Journal of the American Chemical Society, Год журнала: 2021, Номер 143(13), С. 5099 - 5105

Опубликована: Март 24, 2021

The controllable B–H bond activation of carboranes has long been a compelling challenge. However, as the symmetry para-carborane places same charge on all its ten boron atoms, controlling regiochemistry in these molecules remained out reach ever since their discovery. Herein, we describe how to use steric effects achieve regioselective process for para-carborane. In this strategy, B(2,8)–H or B(2,7)–H patterns were achieved by taking advantage π–π interactions between pyridine ligands. Interestingly, employing host–guest metallacage compounds, could be avoided and exclusive B(2,9)–H can achieved. Steric hindrance was also found beneficial species. work, demonstrate that promising driving force bonds open new opportunities field.

Язык: Английский

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Metal-catalyzed B–H acylmethylation of pyridylcarboranes: access to carborane-fused indoliziniums and quinoliziniums

Chemical Science, Год журнала: 2021, Номер 12(47), С. 15563 - 15571

Опубликована: Янв. 1, 2021

Metal-catalyzed selective mono-acylmethylation of pyridylcarboranes has been realized, which provides further utility to construct carborane-fused indoliziniums and quinoliziniums.

Язык: Английский

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An Iridium-Stabilized Borenium Intermediate

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(40), С. 18359 - 18374

Опубликована: Сен. 29, 2022

Exploration of new organometallic systems based on polyhedral boron clusters has the potential to solve challenging chemical problems such as stabilization reactive intermediates and transition-state-like species postulated for E-H (E = H, B, C, Si) bond activation reactions. We report facile clean B-H a hydroborane by iridium cluster complex. The product this reaction is an unprecedented fully characterized transition metal-stabilized cation or borenium. Moreover, intermediate bears unusual intramolecular B···H interaction between hydrogen originating from activated cyclometallated metal-bonded atom cluster. This proposed be arrested insertion into Bcage-metal initiation step "cage-walking" around upper surface process supported hydrogen-deuterium exchange observed at cluster, mechanism basis theoretical methods with special focus role noncovalent interactions. All compounds were isolated NMR spectroscopy elemental analysis. Key studied single crystal X-ray diffraction photoelectron spectroscopy.

Язык: Английский

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Chelating 1,2-Bis(2′-picolyl)-o-carborane as a Supporting Ligand for Pd-Catalyzed Selective B(3,6)–H Difunctionalization of o-Carboranes

Inorganic Chemistry, Год журнала: 2025, Номер unknown

Опубликована: Март 11, 2025

Transition metal catalyzed selective cage B–H functionalization of carboranes has made significant progress in recent years, giving rise to the efficient synthesis a large variety B-functionalized including alkenylation, arylation, alkynylation, borylation, hydroxylation, acyloxylation, amination, and halogenation. However, mechanisms these catalytic B–X coupling reactions are not well understood. Herein, we describe isolation characterization catalytically relevant o-carborane based palladium(II) metallacycle, disclosing details Pd-catalyzed o-carboranes. As result, highly B(3,6)-dihalogenation, -dimethylation, -diarylation o-carboranes have been achieved.

Язык: Английский

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Post-coordination of Ru(II) Controlled Regioselective B(4)–H Acylmethylation of o-Carboranes with Sulfoxonium Ylides

Chemical Science, Год журнала: 2025, Номер unknown

Опубликована: Янв. 1, 2025

Despite significant progress in the B-H functionalization of carboranes, development cost-effective catalytic systems devoid noble metals, coupled with mechanistic validation regioselectivity control, remains a formidable challenge. Herein, we disclose an Ag salt-free, redox-neutral, and inexpensive ruthenium(ii)-catalyzed protocol that enables exclusive B(4)-H acylmethylation o-carboranes through novel post-coordination strategy. By exploiting weakly coordinating carboxylic acid as traceless directing group, this method achieves excellent mono-site selectivity for B-C(sp3) bond formation using diverse sulfoxonium ylides, demonstrating both functional group tolerance synthetic scalability. This work not only establishes practical platform but also addresses critical questions unresolved prior analogous studies. Through deuterium labeling, situ high-resolution mass spectrometry (HRMS) tracking, single-crystal X-ray analysis Ru intermediates, unequivocally demonstrate originates from unique mode Ru(ii). The catalyst simultaneously engages enolizable acylmethyl moiety mono-acylated intermediate, thereby dictating activation trajectory. Our findings establish generalizable regiocontrolled carborane while defining paradigms transition metal-mediated chemistry.

Язык: Английский

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Iron-Catalyzed Selective B–H Activation for 4/5-fold Methylation and Arylation of Carboranes

ACS Catalysis, Год журнала: 2022, Номер 12(15), С. 8761 - 8767

Опубликована: Июль 7, 2022

Catalytic selective B–H functionalization of carboranes has recently attracted enormous research interest, resulting in the development a series methods for transition metal-catalyzed vertex-specific carboranes. These established protocols require noble metal catalysts. Herein, we report highly efficient iron-catalyzed silver-free 4/5-fold cage methylation/arylation using organoaluminum compounds as alkylation/arylation reagents, leading to variety B(3,4,5,6)-tetramethylated/tetraarylated o-carboranes and B(2,3,4,5,6)-pentamethylated/pentaphenylated m-carboranes very good excellent yields. The use inexpensive diethyl oxalate an oxidant makes this protocol practical, realizing easily gram-scale synthesis products. associated reaction mechanism is also proposed. This method represents alternative strategy catalytic polyfunctionalization via base catalysis.

Язык: Английский

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