Lewis Base–Boryl Radicals Enabled Borylation Reactions and Selective Activation of Carbon–Heteroatom Bonds

Accounts of Chemical Research, Journal Year: 2022, Volume and Issue: 56(2), P. 169 - 186

Published: Dec. 26, 2022

ConspectusThe past decades have witnessed tremendous progress on radical reactions. However, in comparison with carbon, nitrogen, oxygen, and other main group element centered radicals, the synthetic chemistry of boron radicals was less studied, mainly due to high electron-deficiency instability such 3-center-5-electron species. In 1980s, Roberts co-workers found that coordination a Lewis base (amines or phosphines) center could form 4-center-7-electron boryl (Lewis base-boryl LBRs) are be more stable. only limited applications were developed. 2008, Curran achieved breakthrough discovery N-heterocyclic carbene (NHC) which enable range reduction polymerization Despite these exciting findings, powerful valuable LBRs would expected, given structures reactivities easily modulated, provide ample opportunities discover new this Account, summary our key contributions LBR-enabled borylation reactions selective activation inert carbon-heteroatom bonds will presented.Organoboron compounds shown versatile chemical society, their syntheses rely principally ionic The development mechanistically different allows synthesizing products inaccessible by traditional methods. For purpose, we progressively developed series NHC-boryl mediated chemo-, regio-, stereoselective alkenes alkynes, wide variety structurally diverse organoboron molecules successfully prepared. utility borylated also demonstrated. Furthermore, disclosed photoredox protocol for oxidative generation enabled useful defluoroborylation arylboration reactions.Selective bond is an ideal way convert simple starting materials value-added products, while cleavage bonds, particular chemoselectivity control when multiple identical present similar environments, remains long-standing challenge. We envisaged finely tuning properties might solution address Recently, 4-dimethylaminopyridine (DMAP)-boryl promoted sequential C-F functionalization trifluoroacetic acid derivatives, α-C-F selectively snipped via spin-center shift mechanism. This strategy enables facile conversion abundantly available highly mono- difluorinated molecules. Encouraged finding, further three-step sequence construct all-carbon quaternary centers from trichloromethyl groups, where three C-Cl cleaved rational choice suitable precursors each step. dehydroxylative alkylation α-hydroxy carboxylic derivatives achieved, allowing efficient some biomass platform value products.

Language: Английский

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Direct B–H Functionalization of Icosahedral Carboranes via Hydrogen Atom Transfer

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(13), P. 7638 - 7647

Published: March 22, 2023

The efficient and selective functionalization of icosahedral carboranes (C2B10H12) at the boron vertexes is a long-standing challenge owing to presence 10 inert B-H bonds in similar chemical environment. Herein, we report new reaction paradigm for direct via homolysis enabled by nitrogen-centered radical-mediated hydrogen atom transfer (HAT) strategy. Both HAT process carborane bond resulting boron-centered carboranyl radical intermediate have been confirmed experimentally. occurs most electron-rich vertex with lowest dissociation energy (BDE). Using this strategy, diverse derivatization, including thiolation, selenation, alkynylation, alkenylation, cyanation, halogenation, achieved satisfactory yields under photoinitiated condition metal-free redox-neutral fashion. Moreover, synthetic utility current protocol was also demonstrated both scale-up construction carborane-based functional molecules. Therefore, methodology opens pathway functionalization, which distinct from heterolytic mechanism traditional strategies.

Language: Английский

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Photocatalytic [3 + 2]-annulation via sodium tetraarylborate: a fundamental approach for synthesizing 1,4,2-diazaborole analogs

Chemical Science, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 1, 2025

Nitriles stabilize neutral diarylboryl radicals, generating the RCN-BAr 2 complex, an efficient boron-nitrogen synthon that reacts with imines and olefins for photocatalytic synthesis of boron–nitrogen heterocycles, such as 1,4,2-diazaboroles.

Language: Английский

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Dative Bonding Activation Enables Precise Functionalization of the Remote B–H Bond of nido-Carborane Clusters

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: unknown

Published: Sept. 13, 2024

The innovation of synthetic strategies for selective B-H functionalization is a pivotal objective in the realm boron cluster chemistry. However, precise, efficient, and rapid bond carboranes that distant from existing functional groups remains intractable owing to limited approaches site-selective control established methods. Herein, we report dative bonding activation strategy nonclassical remote site

Language: Английский

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Alkylboronic acids as alkylating agents: photoredox-catalyzed alkylation reactions assisted by K₃PO₄

Chemical Science, Journal Year: 2022, Volume and Issue: 13(45), P. 13466 - 13474

Published: Jan. 1, 2022

Despite the ubiquity of alkylboronic acids in organic synthesis, their utility as alkyl radical precursors visible-light-induced photocatalytic reactions is limited by high oxidation potentials. In this study, we demonstrated that an inorganophosphorus compound can modulate potentials so they act precursors. We propose a mechanism based on results fluorescence quenching experiments, electrochemical 11B and 31P NMR spectroscopy, other techniques. addition, describe simple reliable alkylation method has good functional group tolerance be used for direct C-B chlorination, cyanation, vinylation, alkynylation, allylation, well late-stage functionalization derivatized drug molecules. Notably, selectively activated presence boronic pinacol ester.

Language: Английский

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Facile Borylation of Alkenes, Alkynes, Imines, Arenes and Heteroarenes with N‐Heterocyclic Carbene‐Boranes and a Heterogeneous Semiconductor Photocatalyst

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(39)

Published: Aug. 9, 2023

Although the development of radical chain and photocatalytic borylation reactions using N-heterocyclic carbene (NHC)-borane as boron source is remarkable, persistent problems, including use hazardous high-energy initiators or recyclability photostability issues soluble homogeneous photocatalysts, still leave great room for further in a sustainable manner. Herein, we report conceptually different approach toward highly functionalized organoborane synthesis by recoverable ultrathin cadmium sulfide (CdS) nanosheets heterogeneous photocatalyst, general mild platform that enables regioselective wide variety alkenes (arylethenes, trifluoromethylalkenes, α,β-unsaturated carbonyl compounds nitriles), alkynes, imines electron-poor aromatic rings with NHC-borane boryl precursor. Mechanistic studies density functional theory (DFT) calculations reveal both photogenerated electrons holes on CdS fully perform their own roles, thereby resulting enhancement activity stability CdS.

Language: Английский

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Visible‐Light‐Induced Photoreduction of Carborane Phosphonium Salts: Efficient Synthesis of Carborane‐Oxindole‐Pharmaceutical Hybrids

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(31)

Published: April 29, 2023

Visible-light-induced photoreaction of carboranes is an effective approach to prepare carborane-containing compounds. While several methods involving boron-centered carboranyl radicals have been established, those for carbon-centered are underdeveloped, except the UV-light-promoted photohomolysis. Herein, we describe a simple but access by photoreduction carborane phosphonium salts under blue light irradiation without using transition metals and photocatalysts. The utility method was demonstrated successfully preparing range carborane-oxindole-pharmaceutical hybrids radical cascade reactions. Computational experimental studies suggest that generated single-electron transfer photoactive charge-transfer complexes between additive potassium acetate.

Language: Английский

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Site‐Selective Functionalization of Carboranes at the Electron‐Rich Boron Vertex: Photocatalytic B−C Coupling via a Carboranyl Cage Radical

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(37)

Published: June 7, 2022

Functionalization of carboranes in a vertex-specific manner is perennial challenge. Here, we report photocatalytic B-C coupling for the selective functionalization at boron site which most distal to carbon. This reaction was achieved by photo-induced decarboxylation carborane carboxylic acids generate vertex-centered carboranyl radicals. Theoretical calculations also demonstrate that more easily occurs bearing higher electron density owing lower energy barrier single-electron transfer radical. By using this strategy, number functionalized could be accessed through alkylation, alkenylation, and heteroarylation under mild conditions. Moreover, both highly efficient blue emitter with solid-state luminous efficiency 42 % drug candidate neutron capture therapy (BNCT) containing targeting fluorine units were obtained.

Language: Английский

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A strategy for regioselective B–H functionalization ofo-carboranesviabase metal catalysis

Organic Chemistry Frontiers, Journal Year: 2023, Volume and Issue: 10(12), P. 3074 - 3079

Published: Jan. 1, 2023

This frontier article summarizes the recent developments in base metal-catalyzed regioselective cage B–H functionalization of carboranes and discusses related challenging issues.

Language: Английский

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Visible-Light-Induced Tandem Nickel-Catalyzed Heck Cyclization/Self-Promoted [2+2] Intermolecular Cycloaddition

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

Published: March 12, 2025

Visible-light-induced transition metal (TM) catalysis has emerged as a new paradigm to discover unprecedented transformations. The reported nickel species TM photocatalysts are mainly involved in the homolysis of Ni(II) complex or alkyl halide activation. Herein, we describe that photoexcited could facilitate Heck cyclization by accelerating anti-β-hydride elimination. Meanwhile, tandem visible-light-induced substrate self-promoted intermolecular [2+2] photocycloaddition without assistance additional was discovered.

Language: Английский

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