N–O Bond Activation by Energy Transfer Photocatalysis

Accounts of Chemical Research, Journal Year: 2022, Volume and Issue: 55(17), P. 2526 - 2541

Published: Aug. 20, 2022

ConspectusA radical shift toward energy transfer photocatalysis from electron under visible-light photoirradiation is often due to the greener prospects of atom and process economy. Recent advances in embrace unique strategies for direct small-molecule activation sometimes extraordinary chemical bond formation absence additional/sacrificial reagents. Selective requires careful selection substrates photocatalysts a perfect match with respect their triplet energies while having incompatible redox potentials prevent competitive pathways. Substrates containing labile N–O bonds are potential targets generating reactive key intermediates via access variety functionalized molecules. Typically, differential densities N O heteroatoms have been exploited generation either N- or O-centered by pathway. However, latest developments involve homolysis generate both radicals subsequent utilization diverse organic transformations, also sacrificial In this Account, we highlight our contributions field intermediates, coverage useful mechanistic insights. More specifically, well-designed bond-containing such as 1,2,4-oxadiazolines, oxime esters, N-indolyl carbonates, N-enoxybenzotriazoles were successfully utilized versatile transformations involving selective over high state energy. Direct N-, O-, C-centered (if decarboxylation follows) was achieved cross-couplings rearrangement processes. particular, open-shell nitrogen including N(sp2) N(sp3) nitrenes, utilized. Notably, diversified identical through control reaction conditions. 1,2,4-Oxadiazolines converted into spiro-azolactams iminyl presence 1O2, benzimidazoles, sulfoximines external sulfoxide reagent nitrene inert Besides, esters underwent intramolecular C(sp3)–N radical–radical coupling intermolecular combined transfer–hydrogen strategy. Furthermore, series electrochemical photophysical experiments well computational studies performed substantiate proposed energy-transfer-driven We hope that Account will serve guide rational design processes further bonds.

Language: Английский

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γ-Amino Alcohols via Energy Transfer Enabled Brook Rearrangement

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(15), P. 10899 - 10907

Published: April 3, 2024

In the long-standing quest to synthesize fundamental building blocks with key functional group motifs, photochemistry in recent past has comprehensively established its attractiveness. Amino alcohols are not only functionally diverse but ubiquitous biologically active realm of compounds. We developed bench-stable bifunctional reagents that could then access sparsely reported γ-amino directly from feedstock alkenes through energy transfer (EnT) photocatalysis. A designed 1,3-linkage across is made possible by intervention a radical Brook rearrangement takes place downstream EnT-mediated homolysis our reagent(s). combination experimental mechanistic investigations and detailed computational studies (DFT) indicates chain propagated reaction pathway.

Language: Английский

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Visible-Light-Induced Energy-Transfer-Mediated Hydrofunctionalization and Difunctionalization of Unsaturated Compounds via Sigma-Bond Homolysis of Energy-Transfer Acceptors

ACS Catalysis, Journal Year: 2025, Volume and Issue: 15(3), P. 1854 - 1941

Published: Jan. 17, 2025

Over the past decade, visible-light-mediated energy-transfer (EnT) catalysis, particularly triplet–triplet (TTEnT) has emerged as a mild and environmentally friendly approach for diverse organic synthetic transformations. In contrast to photoredox which typically requires sacrificial electron donors or acceptors complete catalytic cycle, EnT photocatalysis generally proceeds with high atom economy while minimizing generation of wasteful byproducts. Furthermore, successful catalysis is contingent upon precise control redox potentials both photocatalysts substrates, strategies are primarily influenced by triplet energy compatibility between these entities. Considering growing importance photocatalysis, well hydrofunctionalization difunctionalization reactions in synthesis, this review systematically summarizes significant advancements EnT-enabled unsaturated compounds via sigma-bond homolysis over decade. Special emphasis placed on elucidating substrate scopes mechanistic scenarios. Additionally, discusses versatile applications methodologies addresses current challenges opportunities within evolving research field. This structured into six main categories based different types sigma-bonds undergoing homolysis. These include transformations mediated 1) N–O bond oxime esters other N,O-radical precursors; 2) N–S N-sulfonyl imines N,S-radical 3) chalcogen–chalcogen disulfides oxy/thio/selenosulfonates; 4) C–S tri/difluoromethylated sulfinates, acetylenic triflones, arylsulfonium salts; 5) C–X (X = halogen) halides; 6) acceptors. Through providing theoretical backgrounds along comprehensive overview currently employed acceptors, photosensitizers, contemporary EnT-induced compounds, aims serve an invaluable resource future innovations rapidly

Language: Английский

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Regioselective Access to Vicinal Diamines by Metal‐Free Photosensitized Amidylimination of Alkenes with Oxime Esters

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(44)

Published: Sept. 9, 2022

A metal-free photosensitized protocol for regioselective diamination of alkene feedstocks over a single step was developed based on the rationally designed bifunctional reagent, thus affording range differentially protected 1,2-diamines in moderate to high yields. Mechanistic studies reveal that reaction is initiated with triplet-triplet energy transfer between thioxanthone catalyst and followed by fragmentation simultaneously generate long-lived iminyl radical transient amidyl radical. The excellent regioselectivity presumably stems from large reactivity difference two different N-centered species. This characterized regioselectivity, broad functional group tolerance, mild conditions, which would enrich diversity versatility facilitate diversity-oriented synthesis 1,2-diamine-containing complex molecule scaffolds.

Language: Английский

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Efficient access to β-amino acid ester/β-amino ketone derivatives via photocatalytic radical alkoxycabonylimidation/carbonylimidation of alkenes

Organic Chemistry Frontiers, Journal Year: 2022, Volume and Issue: 9(9), P. 2522 - 2528

Published: Jan. 1, 2022

A photocatalytic protocol for the synthesis of β-amino acid ester and ketone derivatives is developed using simple easy-to-synthesize oxime oxalate phenylglyoxylate as difunctionalization reagents.

Language: Английский

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Photoinduced Electron Transfer from Xanthates to Acyl Azoliums: Divergent Ketone Synthesis via N‐Heterocyclic Carbene Catalysis

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(32)

Published: June 12, 2023

Considering the prevalence of alcohols and carboxylic acids, their fragment cross-coupling reactions could hold significant implications in organic synthesis. Herein, we report a versatile method for synthesizing diverse range ketones from acid derivatives via N-heterocyclic carbene (NHC) catalysis. Mechanistic investigations revealed that photoexcited xanthates acyl azoliums undergo single electron transfer (SET) under photocatalyst-free conditions, generating NHC-derived ketyl radicals alkyl radicals. These open-shell intermediates subsequently radical-radical reaction, yielding valuable ketones. Furthermore, this approach can be employed three-component involving alkenes enynes, resulting structurally cross-coupled The unified strategy offers unique opportunity coupling derivatives, accommodating functional groups even complex settings.

Language: Английский

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Rejuvenation of dearomative cycloaddition reactions via visible light energy transfer catalysis

Chemical Science, Journal Year: 2023, Volume and Issue: 14(43), P. 12004 - 12025

Published: Jan. 1, 2023

Dearomative cycloaddition is a powerful technique to access sp

Language: Английский

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Photosensitized Vicinal Sulfonylamination of Alkenes with Oxime Ester and DABCO·(SO₂)₂

Organic Letters, Journal Year: 2023, Volume and Issue: 25(10), P. 1782 - 1786

Published: March 8, 2023

A metal-free photosensitized three-component reaction of oxime esters, alkenes, and DABCO·(SO2)2 was developed. This protocol could accommodate a wide substrate scope, including activated unactivated alkenes aryl aliphatic carboxylic acid delivering broad range β-amino sulfones in moderate to high yields. The insertion SO2 as linker moiety allows the manipulation functionality process, expanding utility esters bifunctional reagents.

Language: Английский

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Site‐Selective Pyridine C−H Alkylation with Alcohols and Thiols via Single‐Electron Transfer of Frustrated Lewis Pairs

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(51)

Published: Oct. 31, 2022

A unified strategy for the deoxygenative or desulfurative pyridylation of various alcohols and thiols has been developed through a single-electron transfer (SET) process frustrated Lewis pairs (FLPs) derived from pyridinium salts PtBu3 . Mechanistic studies revealed that N-amidopyridinium serve as effective acids formation FLPs with , generated phosphine radical cation ionically couples in situ xanthate, eventually affording alkyl facile β-scission under photocatalyst-free conditions. The reaction efficiency was further accelerated by visible-light irradiation. This method is conceptually appealing using encounter complexes FLP chemistry to promote SET, which provides previously unrecognized opportunity selective heteroarylation diverse range functional groups, even complex settings mild

Language: Английский

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Synthesis of γ-amino acids via photocatalyzed intermolecular carboimination of alkenes

Organic Chemistry Frontiers, Journal Year: 2022, Volume and Issue: 9(16), P. 4328 - 4333

Published: Jan. 1, 2022

We report a direct approach to achieve the energy transfer-driven carboimination of alkenes for synthesis diverse collection valuable γ-amino acids.

Language: Английский

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