Light opens a new window for N-heterocyclic carbene catalysis

Chemical Science, Journal Year: 2020, Volume and Issue: 11(39), P. 10605 - 10613

Published: Jan. 1, 2020

N-Heterocyclic carbenes (NHCs) are efficient Lewis basic catalysts for the umpolung of various polarized unsaturated compounds usually including aldehydes, imines, acyl chlorides and activated esters. NHC catalysis involving electron pair transfer steps has been extensively studied; however, through single-electron (SET) processes, despite having potential to achieve chemical transformations inert bonds using green reagents, long a challenging task in organic synthesis. In parallel, visible-light-induced photocatalysis photoexcitation have established as powerful tools facilitate sustainable synthesis, they enable generation reactive radical intermediates under extremely mild conditions. Recently, number elegant visible-light-induced, NHC-catalyzed were developed accessing valuable compounds. As result, this minireview will highlight recent advances field.

Language: Английский

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Recent advances in N-heterocyclic carbene-catalyzed radical reactions

Chinese Chemical Letters, Journal Year: 2020, Volume and Issue: 32(2), P. 660 - 667

Published: Aug. 19, 2020

Language: Английский

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Direct α-Acylation of Alkenes via N-Heterocyclic Carbene, Sulfinate, and Photoredox Cooperative Triple Catalysis

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(13), P. 4903 - 4909

Published: March 24, 2021

N-Heterocyclic carbene (NHC) catalysis has emerged as a versatile tool in modern synthetic chemistry. Further increasing the complexity, several processes have been introduced that proceed via dual catalysis, where NHC organocatalyst operates concert with second catalytic moiety, significantly enlarging reaction scope. In biological transformations, multiple is generally used to access complex natural products. Guided by strategy, triple studied recently, three different modes are merged single process. this Communication, direct α-C–H acylation of various alkenes aroyl fluorides using NHC, sulfinate, and photoredox cooperative reported. The method allows preparation α-substituted vinyl ketones moderate high yields excellent functional group tolerance. Mechanistic studies reveal these cascades through sequential radical addition/coupling/elimination contrast known operate two sets interwoven cycles, process, all cycles interwoven.

Language: Английский

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Modular Organoboron Catalysts Enable Transformations with Unprecedented Reactivity

Accounts of Chemical Research, Journal Year: 2021, Volume and Issue: 54(23), P. 4434 - 4448

Published: Nov. 21, 2021

ConspectusElectron-deficient boron-based catalysts with metal-free but metallomimetic characteristics provide a versatile platform for chemical transformations. However, their catalytic performance is usually lower than that of the corresponding metal-based catalysts. Furthermore, many elaborate organoboron compounds are produced via time-consuming multistep syntheses low yields, presenting formidable challenge large-scale applications these Given this context, development combined advantages high efficiency and easy preparation critical importance.Therefore, we envisioned construction dynamic Lewis multicore system (DLMCS) by integrating acidic boron center(s) basic ammonium salt in one molecule would be particularly efficient on-demand because intramolecular synergistic effect. This Account summarizes our recent efforts developing modular unprecedented activities several A series mono-, di-, tri-, tetranuclear was readily designed prepared nearly quantitative yields over two steps using commercially available feedstocks. Notably, can modularly tailored fine control electrophilic property center(s), electronic steric effects electropositive cation, linker length between center number centers, nucleophilic anion. design allows systematic manipulation reactivity efficacy catalysts, thus optimizing suitable These include coupling CO2 epoxides, copolymerization ring-opening polymerization (ROP) (ROCOP) epoxides cyclic anhydrides.The utilization mononuclear provided turnover frequency 11050 h-1 CO2/propylene oxide reaction, an 5.0 kg polymer/g catalyst cyclohexene oxide, record-breaking 7.4 ROCOP anhydrides. 56500 observed at loading 10 ppm ROP dinuclear The realized previously intractable task epichlorohydrin, producing poly(chloropropylene carbonate) highest molecular weight 36.5 kg/mol reported to date.Furthermore, study revealed interaction multicore, is, effect quaternary salt, plays key role mediating activity selectivity. based on investigations crystal structures intermediates, reaction kinetics, density functional theory calculations. tactics presented should inspire more advanced designs.

Language: Английский

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Tale of the Breslow intermediate, a central player in N-heterocyclic carbene organocatalysis: then and now

Chemical Science, Journal Year: 2021, Volume and Issue: 12(23), P. 7973 - 7992

Published: Jan. 1, 2021

Molecular insights on the formation, detection, and even isolation of Breslow intermediate, which is most important species in N-heterocyclic carbene (NHC) catalysis, as obtained from experimental computational studies, are presented.

Language: Английский

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Hydrogen‐Bond Regulation of the Microenvironment of Ni(II)‐Porphyrin Bifunctional Electrocatalysts for Efficient Overall Water Splitting

Advanced Materials, Journal Year: 2023, Volume and Issue: 35(19)

Published: Feb. 15, 2023

Accurately regulating the microenvironment around active sites is an important approach for boosting overall water splitting performance of bifunctional electrocatalysts, which can drive both oxygen evolution reaction (OER) and hydrogen (HER) in same electrolyte. Herein, pseudo-pyridine-substituted Ni(II)-porphyrins (o-NiTPyP, m-NiTPyP, p-NiTPyP) with pseudo-pyridine N-atoms located at ortho-, meta-, or para-position are prepared used as model catalysts alkaline splitting. Experimental theoretical results reveal that N-atom positions regulate adsorption free energy H-donating substances by affecting H-bonding interaction NNiN bond angles sites, thus those deliver better electrocatalytic activity than Ni(II)-tetraphenylporphyrin (NiTPP) without N-atoms. Among them, m-NiTPyP on carbon nanotubes delivers lowest overpotentials 267 138 mV 10 mA cm-2 OER HER, respectively. Specifically, electrocatalyst electrolyzer requires only 1.62 V to efficient while remaining durable. This work proposes a new H-bond-regulating electrocatalysts effectively deeply understanding its related mechanism.

Language: Английский

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NHC and visible light-mediated photoredox co-catalyzed 1,4-sulfonylacylation of 1,3-enynes for tetrasubstituted allenyl ketones

Chemical Science, Journal Year: 2022, Volume and Issue: 13(11), P. 3169 - 3175

Published: Jan. 1, 2022

The modulation of selectivity highly reactive carbon radical cross-coupling for the construction C-C bonds represents a challenging task in organic chemistry. N-Heterocyclic carbene (NHC) catalyzed transformations have opened new avenue acyl With this method, selective an with alkyl efficient was successfully realized. However, reaction radicals vinyl has been much less investigated. We herein describe NHC and visible light-mediated photoredox co-catalyzed 1,4-sulfonylacylation 1,3-enynes, providing structurally diversified valuable tetrasubstituted allenyl ketones. Mechanistic studies indicated that ketyl are formed from aroyl fluorides via oxidative quenching photocatalyst excited state, generated chemo-specific sulfonyl addition to finally, key provides

Language: Английский

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Organocatalytic diastereo- and atroposelective construction of N–N axially chiral pyrroles and indoles

Nature Communications, Journal Year: 2024, Volume and Issue: 15(1)

Published: Jan. 15, 2024

Abstract The construction of N–N axially chiral motifs is an important research topic, owing to their wide occurrence in natural products, pharmaceuticals and ligands. One efficient method the atroposelective dihydropyrimidin-4-one formation. We present herein a direct catalytic synthesis atropisomers with simultaneous creation contiguous axial central chirality by oxidative NHC ( N -heterocyclic carbenes) catalyzed (3 + 3) cycloaddition. Using our method, we are able synthesize structurally diverse pyrroles indoles vicinal or bearing 2,3-dihydropyrimidin-4-one moiety moderate good yields excellent enantioselectivities. Further synthetic transformations obtained derivative products demonstrated. reaction mechanism origin enantioselectivity understood through DFT calculations.

Language: Английский

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Radical Reactions with N-Heterocyclic Carbene (NHC)-Derived Acyl Azoliums for Access to Multifunctionalized Ketones

ACS Catalysis, Journal Year: 2024, Volume and Issue: 14(11), P. 8270 - 8293

Published: May 13, 2024

As one of the most important key intermediates, NHC-bound acylazolium-based ionic transformations have been intensively explored in past two decades. With expeditious development NHC-catalyzed radical recent years, acylazolium chemistry has reached another level, with number relevant publications increasing significantly. However, a summary focused on acylations NHC-derived acyl azoliums classified according to mechanistic difference not reported. Such detailed classification and deep analysis provide opportunities for better understanding history trend this field. In review, reactions N-heterocyclic carbene (NHC)-derived are systematically introduced. The achievements challenges within area also summarized discussed at end.

Language: Английский

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Carbene organic catalytic planar enantioselective macrolactonization

Nature Communications, Journal Year: 2024, Volume and Issue: 15(1)

Published: Feb. 1, 2024

Macrolactones exhibit distinct conformational and configurational properties are widely found in natural products, medicines, agrochemicals. Up to now, the major effort for macrolactonization is directed toward identifying suitable carboxylic acid/alcohol coupling reagents address challenges associated with macrocyclization, wherein stereochemistry of products usually controlled by substrate's inherent chirality. It remains largely unexplored using catalysts govern both macrolactone formation stereochemical control. Here, we disclose a non-enzymatic organocatalytic approach construct macrolactones bearing chiral planes from achiral substrates. Our strategy utilizes N-heterocyclic carbene (NHC) as potent acylation catalyst that simultaneously mediates macrocyclization controls planar chirality during catalytic process. varying ring sizes sixteen twenty members obtained good-to-excellent yields enantiomeric ratios. study shall open new avenues accessing various stereogenic elements structures readily available small-molecule catalysts.

Language: Английский

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