The Impact of Boron Hybridisation on Photocatalytic Processes

Angewandte Chemie International Edition, Год журнала: 2022, Номер 61(38)

Опубликована: Июнь 24, 2022

Recently the fruitful merger of organoboron chemistry and photocatalysis has come to forefront organic synthesis, resulting in development new technologies access complex (non)borylated frameworks. Central success this combination is control boron hybridisation. Contingent on photoactivation mode, as its neutral planar form or tetrahedral boronate can be used regulate reactivity. This Minireview highlights current state art photocatalytic processes utilising compounds, paying particular attention role hybridisation for target transformation.

Язык: Английский

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Direct Observation of Triplet States in the Isomerization of Alkenylboronates by Energy Transfer Catalysis

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(39), С. 21576 - 21586

Опубликована: Сен. 20, 2023

Alkenylboronates are versatile building blocks for stereocontrolled synthesis owing to the traceless nature of boron group that can be leveraged achieve highly selective geometric isomerization. Using thioxanthone as an inexpensive photocatalyst, photoisomerization these species continues provide expansive platform stereodivergent synthesis, particularly in construction bioactive polyenes. Although mechanistic investigations consistent with light-driven energy transfer, direct experimental evidence remains conspicuously absent. Herein, we report a rigorous investigation using two widely used alkenylboronates alongside relevant reference compounds. Through combination irradiation experiments, transient absorption spectroscopic studies, kinetic modeling, and DFT calculations all isomers model compounds, it has been possible unequivocally detect characterize perpendicular triplet generated by transfer. Our results serve not only blueprint studies challenging organic sensitizers, but guidelines delineated have also enabled development more sustainable reaction conditions: first time, efficient organocatalytic isomerization under sunlight become feasible.

Язык: Английский

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Photogeneration of α-Bimetalloid Radicals via Selective Activation of Multifunctional C1 Units

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(23), С. 15850 - 15859

Опубликована: Май 28, 2024

Light-driven strategies that enable the chemoselective activation of a specific bond in multifunctional systems are comparatively underexplored comparison to transition-metal-based technologies, yet desirable when considering controlled exploration chemical space. With current drive discover next-generation therapeutics, reaction design enables strategic incorporation an sp3 carbon center, containing multiple synthetic handles for subsequent space would be highly enabling. Here, we describe photoactivation ambiphilic C1 units generate α-bimetalloid radicals using only Lewis base and light source directly activate C–I bond. Interception these transient with various SOMOphiles rapid synthesis organic scaffolds (B, Si, Ge) orthogonal activation. In-depth theoretical mechanistic studies reveal prominent role 2,6-lutidine forming photoactive charge transfer complex stabilizing situ generated iodine radicals, as well influential boron p-orbital activation/weakening This simple efficient methodology enabled expedient access functionalized 3D frameworks can further derivatized available technologies C–B C–Si

Язык: Английский

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PolyBorylated Alkenes as Energy‐Transfer Reactive Groups: Access to Multi‐Borylated Cyclobutanes Combined with Hydrogen Atom Transfer Event

Angewandte Chemie International Edition, Год журнала: 2024, Номер 63(25)

Опубликована: Апрель 11, 2024

Abstract While polyborylated alkenes are being recognized for their elevated status as highly valuable reagents in modern organic synthesis, allowing efficient access to a diverse array of transformations, including the formation C−C and C‐heteroatom bonds, potential energy‐transfer reactive groups has remained unexplored. Yet, this holds key generating elusive biradical species, which can be captured by olefins, thereby leading construction new highly‐borylated scaffolds. Herein, we report designed strategy photosensitized [2+2]‐cycloadditions poly‐borylated with various olefins enabling regioselective synthesis cyclobutane motifs, 1,1‐di‐, 1,1,2‐tri‐, 1,1,2,2‐tetra‐borylated cyclobutanes. In fact, these compounds belong family that presently lacks synthetic pathways. Interestingly, when α‐methylstyrene was used, reaction involves an interesting 1,5‐hydrogen atom transfer (HAT). Mechanistic deuterium‐labeling studies have provided insight into outcome process. addition, cyclobutanes then demonstrated useful selective oxidation processes resulting cyclobutanones γ‐lactones.

Язык: Английский

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Electrochemical generation of aryl radicals from organoboron reagents enabled by pulsed electrosynthesis

Angewandte Chemie International Edition, Год журнала: 2024, Номер 63(31)

Опубликована: Май 16, 2024

Aryl radicals play a pivotal role as reactive intermediates in chemical synthesis, commonly arising from aryl halides and diazo compounds. Expanding the repertoire of sources for radical generation to include abundant stable organoboron reagents would significantly advance chemistry broaden their reactivity profile. While traditional approaches utilize stoichiometric oxidants or photocatalysis generate these reagents, electrochemical conditions have been largely underexplored. Through rigorous mechanistic investigations, we identified fundamental challenges hindering generation. In addition high oxidation potentials aromatic compounds, electrode passivation through grafting, homocoupling radicals, decomposition issues were identified. We demonstrate that pulsed electrosynthesis enables selective efficient by mitigating challenges. Our discoveries facilitated development first conversion potassium trifluoroborate salts into C-P bonds. This sustainable straightforward oxidative approach exhibited broad substrate scope, accommodating various heterocycles chlorides, typical substrates transition-metal catalyzed cross-coupling reactions. Furthermore, extended this methodology form C-Se, C-Te, C-S bonds, showcasing its versatility potential bond formation processes.

Язык: Английский

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The Strategies towards Electrochemical Generation of Aryl Radicals

Chemistry - A European Journal, Год журнала: 2024, Номер unknown

Опубликована: Июль 16, 2024

The advancement in electrochemical techniques has unlocked a new path for achieving unprecedented oxidations and reductions of aryl radical precursors controlled selective manner. This approach facilitates the construction aromatic carbon-carbon carbon-heteroatom bonds. In light green merits growing importance this technique chemistry, review aims to provide an overview recent advance generation radicals organized by precursor type, with focus on substrate scope, limitation, underlying mechanism, thereby inspiring future work generation.

Язык: Английский

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Copper-Catalyzed C–B(sp³) Bond Formation through the Intermediacy of Cu–B(sp³) Complex

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

Опубликована: Апрель 15, 2025

The vast majority of transition metal (TM) catalyzed borylative transformations rely on TM-B(sp2) complexes. Contrastingly, the chemistry TM-B(sp3) species and their potential in catalytic borylation remain surprisingly underdeveloped, due probably to lack suitable boron(sp3) reagents. Herein, we employ our recently developed sp2-sp3 diboron reagent successfully enable a copper-catalyzed hydroboration allenes for C-B(sp3) bond formation. A comprehensive mechanistic study, including isolation structural characterization Cu-B(sp3) complex, substantiates presence intermediate cycle.

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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Orange Light-Driven C(sp²)–C(sp³) Cross-Coupling via Spin-Forbidden Ir(III) Metallaphotoredox Catalysis

Journal of the American Chemical Society, Год журнала: 2023, Номер 145(36), С. 19925 - 19931

Опубликована: Авг. 29, 2023

We report the development and characterization of a library Ir(III) photocatalysts capable undergoing spin-forbidden excitation (SFE) under orange light irradiation (595 nm). These catalysts were successfully applied to construction synthetically valuable C(sp2)-C(sp3) bonds inaccessible with existing methods low-energy light-driven dual nickel/photoredox catalysis, demonstrating synthetic utility this photocatalyst family. The are accessing both oxidatively reductively activated coupling partners, illustrated through deaminative arylation potassium alkyl trifluoroborate cross-coupling reactions aryl halides. demonstrate diverse substrate scopes paradigms mild conditions in first example metallaphotoredox coupling.

Язык: Английский

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Photocatalyzed regioselective hydrosilylation for the divergent synthesis of geminal and vicinal borosilanes

Nature Communications, Год журнала: 2023, Номер 14(1)

Опубликована: Май 2, 2023

Geminal and vicinal borosilanes are useful building blocks in synthetic chemistry material science. Hydrosilylation/hydroborylation of unsaturated systems offer expedient access to these motifs. In contrast the well-established transition-metal-catalyzed methods, radical approaches rarely explored. Herein we report synthesis geminal from α-selective hydrosilylation alkenyl boronates via photoinduced hydrogen atom transfer (HAT) catalysis. Mechanistic studies implicate that α-selectivity originates a kinetically favored addition an energetically HAT process. We further demonstrate selective through allyl 1,2-boron migration. These strategies exhibit broad scopes across primary, secondary, tertiary silanes various boron compounds. The utility is evidenced by multi-borosilanes diverse fashion scaling up continuous-flow synthesis.

Язык: Английский

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