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Grotjahn S, Graf C, Zelenka J, Pattanaik A, Müller L, Kutta RJ, Rehbein J, Roithová J, Gschwind RM, Nuernberger P, König B. Reactivity of Superbasic Carbanions Generated via Reductive Radical-Polar Crossover in the Context of Photoredox Catalysis. Angew Chem Int Ed Engl 2024; 63:e202400815. [PMID: 38408163 DOI: 10.1002/anie.202400815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2024] [Revised: 02/06/2024] [Accepted: 02/09/2024] [Indexed: 02/28/2024]
Abstract
Photocatalytic reactions involving a reductive radical-polar crossover (RRPCO) generate intermediates with carbanionic reactivity. Many of these proposed intermediates resemble highly reactive organometallic compounds. However, conditions of their formation are generally not tolerated by their isolated organometallic versions and often a different reactivity is observed. Our investigations on their nature and reactivity under commonly used photocatalytic conditions demonstrate that these intermediates are indeed best described as free, superbasic carbanions capable of deprotonating common polar solvents usually assumed to be inert such as acetonitrile, dimethylformamide, and dimethylsulfoxide. Their basicity not only towards solvents but also towards electrophiles, such as aldehydes, ketones, and esters, is comparable to the reactivity of isolated carbanions in the gas-phase. Previously unsuccessful transformations thought to result from a lack of reactivity are explained by their high reactivity towards the solvent and weakly acidic protons of reaction partners. An intuitive explanation for the mode of action of photocatalytically generated carbanions is provided, which enables methods to verify reaction mechanisms proposed to involve an RRPCO step and to identify the reasons for the limitations of current methods.
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Affiliation(s)
- Sascha Grotjahn
- Faculty of Chemistry and Pharmacy, Institute of Organic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Christina Graf
- Faculty of Chemistry and Pharmacy, Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Jan Zelenka
- Department of Spectroscopy and Catalysis, Radboud University Nijmegen, Heyendaalseweg 135, 6525AJ, Nijmegen, the Netherlands
| | - Aryaman Pattanaik
- Faculty of Chemistry and Pharmacy, Institute of Organic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Lea Müller
- Faculty of Chemistry and Pharmacy, Institute of Organic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Roger Jan Kutta
- Faculty of Chemistry and Pharmacy, Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Julia Rehbein
- Faculty of Chemistry and Pharmacy, Institute of Organic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Jana Roithová
- Department of Spectroscopy and Catalysis, Radboud University Nijmegen, Heyendaalseweg 135, 6525AJ, Nijmegen, the Netherlands
| | - Ruth M Gschwind
- Faculty of Chemistry and Pharmacy, Institute of Organic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Patrick Nuernberger
- Faculty of Chemistry and Pharmacy, Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Burkhard König
- Faculty of Chemistry and Pharmacy, Institute of Organic Chemistry, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
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2
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Liu G, Gao Y, Su W. Photocatalytic Decarboxylative Coupling of Arylacetic Acids with Aromatic Aldehydes. J Org Chem 2022; 88:6322-6332. [PMID: 36173738 DOI: 10.1021/acs.joc.2c01751] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
An efficient protocol was proposed for the preparation of secondary alcohols in good to excellent yields via photoredox-catalyzed decarboxylative couplings between readily available arylacetic acids and a variety of less reactive (hetero)aromatic aldehydes. The formation of carbanion is the key intermediate in this reaction. Various substituted arylacetic acids and aldehydes were all compatible with this transformation under mild reaction conditions. Furthermore, the current protocol was successfully applied to the direct alcoholization of several drug acids.
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Affiliation(s)
- Ge Liu
- College of Chemistry, Fuzhou University, Fuzhou 350116, China.,State Key Laboratory of Structural Chemistry, Center for Excellence in Molecular Synthesis, Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 155 Yangqiao Road West, Fuzhou 350002, China
| | - Yuzhen Gao
- State Key Laboratory of Structural Chemistry, Center for Excellence in Molecular Synthesis, Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 155 Yangqiao Road West, Fuzhou 350002, China
| | - Weiping Su
- State Key Laboratory of Structural Chemistry, Center for Excellence in Molecular Synthesis, Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 155 Yangqiao Road West, Fuzhou 350002, China
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3
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Radhoff N, Studer A. 1,4-Aryl migration in ketene-derived enolates by a polar-radical-crossover cascade. Nat Commun 2022; 13:3083. [PMID: 35655065 PMCID: PMC9163183 DOI: 10.1038/s41467-022-30817-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 05/16/2022] [Indexed: 11/22/2022] Open
Abstract
The arylation of carboxylic acid derivatives via Smiles rearrangement has gained great interest in recent years. Both radical and ionic approaches, as well as radical-polar crossover concepts, have been developed. In contrast, a reversed polar-radical crossover approach remains underexplored. Here we report a simple, efficient and scalable method for the preparation of sterically hindered and valuable α-quaternary amides via a polar-radical crossover-enolate oxidation-aryl migration pathway. A variety of easily accessible N-alkyl and N-arylsulfonamides are reacted with disubstituted ketenes to give the corresponding amide enolates, which undergo upon single electron transfer oxidation, a 1,4-aryl migration, desulfonylation, hydrogen atom transfer cascade to provide α-quaternary amides in good to excellent yields. Various mono- and di-substituted heteroatom-containing and polycyclic arenes engage in the aryl migration reaction. Functional group tolerance is excellent and substrates as well as reagents are readily available rendering the method broadly applicable. The α-arylation of amides via aryl migration has attracted considerable interest in recent years. Here, the authors report a method for the preparation of bulky α-quaternary amides via a polar-radical crossover enolate oxidation-aryl migration cascade.
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Affiliation(s)
- Niklas Radhoff
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149, Münster, Germany
| | - Armido Studer
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149, Münster, Germany.
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Wales SM, Saunthwal RK, Clayden J. C(sp 3)-Arylation by Conformationally Accelerated Intramolecular Nucleophilic Aromatic Substitution (S NAr). Acc Chem Res 2022; 55:1731-1747. [PMID: 35620846 PMCID: PMC9219115 DOI: 10.1021/acs.accounts.2c00184] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
![]()
The asymmetric synthesis of heavily substituted benzylic stereogenic
centers, prevalent in natural products, therapeutics, agrochemicals,
and catalysts, is an ongoing challenge. In this Account, we outline
our contribution to this endeavor, describing our discovery of a series
of new reactions that not only have synthetic applicability but also
present significant mechanistic intrigue. The story originated from
our longstanding interest in the stereochemistry and reactivity of
functionalized organolithiums. While investigating the lithiation
chemistry of ureas (a “Cinderella” sister of the more
established amides and carbamates), we noted an unexpected Truce–Smiles
(T-S) rearrangement involving the 1,4-N → C transposition of
a urea N′-aryl group to the α-carbanion
of an adjacent N-benzyl group. Despite this reaction
formally constituting an SNAr substitution, we found it
to be remarkably tolerant of the electronic properties of the migrating
aryl substituent and the degree of substitution at the carbanion.
Moreover, in contrast to classical SNAr reactions, the
rearrangement was sufficiently rapid that it took place under conditions
compatible with configurational stability in an organolithium intermediate,
enabling enantiospecific arylation at benzylic stereogenic centers.
Experimental and computational studies confirmed a low kinetic barrier
to the aryl migration arising from the strong preference for a trans arrangement of the urea N′-aryl
and carbonyl groups, populating a reactive conformer in which spatial
proximity was enforced between the carbanion and N′-aryl group, hugely accelerating ipso-substitution. This discovery led us to uncover a whole series of conformationally
accelerated intramolecular N → C aryl transfers using different
anilide-based functional groups, including a diverse range of urea,
carbamate, and thiocarbamate-substituted anions. Products included
enantioenriched α-tertiary amines (including α-arylated
N-heterocycles) and alcohols, as well as rare α-tertiary thiols.
Synthetically challenging diarylated centers with differentiated aryl
groups featured heavily in all product sets. The absolute enantiospecificity
(retention versus inversion) of the reaction was dependent on the
heteroatom α to the lithiation site: the origin of this stereodivergence
was probed both experimentally and computationally. Asymmetric variants
of the rearrangement were realized by enantioselective deprotonation,
and connective strategies were developed in which an intermolecular
C–C bond-forming event preceded the anionic rearrangement.
Substrates where the N′-nucleofuge (at the
aryl ipso position) was tethered to the migrating
arene allowed us to use the rearrangement as a ring expansion method
to generate 8- to 12-membered medium-ring N-heterocycles from very
simple precursors. Stabilized carbon nucleophiles such as alkali metal
enolates also readily promoted intramolecular N → C aryl transfer
in N′-arylureas, opening up access to biologically
relevant hydantoins, and enabling a “chiral memory”
approach for the (hetero)arylation of chiral α-amino acids with
programmable retention or inversion of configuration. Collectively,
our studies of electronically versatile T-S rearrangements in anilide-based
systems have culminated in a practical and general strategy for transition
metal-free C(sp3)-arylation. More broadly, our results
highlight the power of conformational activation to achieve unprecedented
reactivity in the construction of challenging C–C bonds.
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Affiliation(s)
- Steven M. Wales
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K
| | - Rakesh K. Saunthwal
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K
| | - Jonathan Clayden
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, U.K
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Greaney MF, Whalley DM. Recent Advances in the Smiles Rearrangement: New Opportunities for Arylation. SYNTHESIS-STUTTGART 2022. [DOI: 10.1055/a-1710-6289] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
AbstractThe Smiles rearrangement has undergone a renaissance in recent years providing new avenues for non-canonical arylation techniques in both the radical and polar regimes. This short review will discuss recent applications of the reaction (from 2017 to late 2021), including its relevance to areas such as heterocycle synthesis and the functionalization of alkenes and alkynes as well as glimpses at new directions for the field.1 Introduction2 Polar Smiles Rearrangements3 Radical Smiles: Alkene and Alkyne Functionalization4 Radical Smiles: Rearrangements via C–X Bond Cleavage5 Radical Smiles: Miscellaneous Rearrangements6 Conclusions
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6
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Allen AR, Noten EA, Stephenson CRJ. Aryl Transfer Strategies Mediated by Photoinduced Electron Transfer. Chem Rev 2022; 122:2695-2751. [PMID: 34672526 PMCID: PMC9272681 DOI: 10.1021/acs.chemrev.1c00388] [Citation(s) in RCA: 52] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Radical aryl migrations are powerful techniques to forge new bonds in aromatic compounds. The growing popularity of photoredox catalysis has led to an influx of novel strategies to initiate and control aryl migration starting from widely available radical precursors. This review encapsulates progress in radical aryl migration enabled by photochemical methods─particularly photoredox catalysis─since 2015. Special attention is paid to descriptions of scope, mechanism, and synthetic applications of each method.
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Affiliation(s)
- Anthony R. Allen
- Department of Chemistry, Willard Henry Dow Laboratory, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| | - Efrey A. Noten
- Department of Chemistry, Willard Henry Dow Laboratory, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| | - Corey R. J. Stephenson
- Department of Chemistry, Willard Henry Dow Laboratory, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States.,
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7
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Louvel D, Souibgui A, Taponard A, Rouillon J, ben Mosbah M, Moussaoui Y, Pilet G, Khrouz L, Monnereau C, Vantourout JC, Tlili A. Tailoring the Reactivity of the Langlois Reagent and Styrenes with Cyanoarenes Organophotocatalysts under Visible‐Light. Adv Synth Catal 2022. [DOI: 10.1002/adsc.202100828] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Dan Louvel
- Institute of Chemistry and Biochemistry (ICBMS–UMR CNRS 5246) Univ Lyon Université Lyon 1, CNRS, CPE-Lyon, INSA 43 Bd du 11 Novembre 1918 69622 Villeurbanne France
| | - Amel Souibgui
- Institute of Chemistry and Biochemistry (ICBMS–UMR CNRS 5246) Univ Lyon Université Lyon 1, CNRS, CPE-Lyon, INSA 43 Bd du 11 Novembre 1918 69622 Villeurbanne France
- Organic Chemistry Laboratory (LR17ES08) Faculty of Sciences of Sfax University of Sfax Sfax 3029 Tunisia
- Faculty of Sciences of Gafsa University of Gafsa Gafsa 2112 Tunisia
| | - Alexis Taponard
- Institute of Chemistry and Biochemistry (ICBMS–UMR CNRS 5246) Univ Lyon Université Lyon 1, CNRS, CPE-Lyon, INSA 43 Bd du 11 Novembre 1918 69622 Villeurbanne France
| | - Jean Rouillon
- Univ Lyon ENS de Lyon, CNRS UMR 5182, Université Lyon 1, Laboratoire de Chimie F-69342 Lyon France
| | - Mongi ben Mosbah
- Organic Chemistry Laboratory (LR17ES08) Faculty of Sciences of Sfax University of Sfax Sfax 3029 Tunisia
- Laboratory for the Application of Materials to the Environment, Water and Energy (LR21ES15) Faculty of Sciences of Gafsa University of Gafsa Gafsa 2112 Tunisia
| | - Younes Moussaoui
- Organic Chemistry Laboratory (LR17ES08) Faculty of Sciences of Sfax University of Sfax Sfax 3029 Tunisia
- Faculty of Sciences of Gafsa University of Gafsa Gafsa 2112 Tunisia
| | - Guillaume Pilet
- Univ Lyon Université Lyon 1, Laboratoire des Multimatériaux et Interfaces (LMI), UMR 5615, CNRS, Bâtiment Chevreul Avenue du 11 novembre 1918 69622 Villeurbanne cedex France
| | - Lhoussain Khrouz
- Univ Lyon ENS de Lyon, CNRS UMR 5182, Université Lyon 1, Laboratoire de Chimie F-69342 Lyon France
| | - Cyrille Monnereau
- Univ Lyon ENS de Lyon, CNRS UMR 5182, Université Lyon 1, Laboratoire de Chimie F-69342 Lyon France
| | - Julien C. Vantourout
- Institute of Chemistry and Biochemistry (ICBMS–UMR CNRS 5246) Univ Lyon Université Lyon 1, CNRS, CPE-Lyon, INSA 43 Bd du 11 Novembre 1918 69622 Villeurbanne France
| | - Anis Tlili
- Institute of Chemistry and Biochemistry (ICBMS–UMR CNRS 5246) Univ Lyon Université Lyon 1, CNRS, CPE-Lyon, INSA 43 Bd du 11 Novembre 1918 69622 Villeurbanne France
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8
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Li M, Zhao D, Sun K. Visible Light Driving Alkene Difunctionalization Reaction Involving Group Migration. CHINESE J ORG CHEM 2022. [DOI: 10.6023/cjoc202207037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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9
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Wei D, Liu T, He Y, Wei B, Pan J, Zhang J, Jiao N, Han B. Radical 1,4/5-Amino Shift Enables Access to Fluoroalkyl-Containing Primary β(γ)-Aminoketones under Metal-Free Conditions. Angew Chem Int Ed Engl 2021; 60:26308-26313. [PMID: 34437754 DOI: 10.1002/anie.202110583] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Indexed: 12/21/2022]
Abstract
A novel radical 1,4/5-amino shift from the oxygen center of alkene-tethered diphenyl ketoxime ethers to the carbon center to achieve high value-added fluoroalkyl-containing primary β(γ)-amino-ketones is reported. Mechanism studies reveal that the migration is triggered by the alkene addition of fluoroalkyl radical derived from the electron donor-acceptor (EDA) complex of Togni's reagent II or fluoroalkyl iodides and quinuclidine, and involves a unique 5(6)-exo-trig cyclization of the carbon-centered radical onto the N-atom of ketoxime ethers followed by a cascade sequence of N-O bond cleavage and dehydrogenation. Notably, besides Togni's reagent II and fluoroalkyl iodides, this protocol is also compatible with other radical precursors to provide various functionalized primary aminoketones.
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Affiliation(s)
- Dian Wei
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, China
| | - Tuming Liu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, China
| | - Yiheng He
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, China
| | - Bangyi Wei
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, China
| | - Jiahao Pan
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, China
| | - Jianwu Zhang
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, China
| | - Ning Jiao
- State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, Peking University, Beijing, 100191, China
| | - Bing Han
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, China
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10
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Wei D, Liu T, He Y, Wei B, Pan J, Zhang J, Jiao N, Han B. Radical 1,4/5‐Amino Shift Enables Access to Fluoroalkyl‐Containing Primary β(γ)‐Aminoketones under Metal‐Free Conditions. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202110583] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Dian Wei
- State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 China
| | - Tuming Liu
- State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 China
| | - Yiheng He
- State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 China
| | - Bangyi Wei
- State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 China
| | - Jiahao Pan
- State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 China
| | - Jianwu Zhang
- State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 China
| | - Ning Jiao
- State Key Laboratory of Natural and Biomimetic Drugs School of Pharmaceutical Sciences Peking University Beijing 100191 China
| | - Bing Han
- State Key Laboratory of Applied Organic Chemistry College of Chemistry and Chemical Engineering Lanzhou University Lanzhou 730000 China
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11
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Radical and Ionic Mechanisms in Rearrangements of o-Tolyl Aryl Ethers and Amines Initiated by the Grubbs-Stoltz Reagent, Et 3SiH/KO tBu. Molecules 2021; 26:molecules26226879. [PMID: 34833971 PMCID: PMC8619283 DOI: 10.3390/molecules26226879] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 11/03/2021] [Accepted: 11/05/2021] [Indexed: 11/16/2022] Open
Abstract
Rearrangements of o-tolyl aryl ethers, amines, and sulfides with the Grubbs–Stoltz reagent (Et3SiH + KOtBu) were recently announced, in which the ethers were converted to o-hydroxydiarylmethanes, while the (o-tol)(Ar)NH amines were transformed into dihydroacridines. Radical mechanisms were proposed, based on prior evidence for triethylsilyl radicals in this reagent system. A detailed computational investigation of the rearrangements of the aryl tolyl ethers now instead supports an anionic Truce–Smiles rearrangement, where the initial benzyl anion can be formed by either of two pathways: (i) direct deprotonation of the tolyl methyl group under basic conditions or (ii) electron transfer to an initially formed benzyl radical. By contrast, the rearrangements of o-tolyl aryl amines depend on the nature of the amine. Secondary amines undergo deprotonation of the N-H followed by a radical rearrangement, to form dihydroacridines, while tertiary amines form both dihydroacridines and diarylmethanes through radical and/or anionic pathways. Overall, this study highlights the competition between the reactive intermediates formed by the Et3SiH/KOtBu system.
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12
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Whalley DM, Seayad J, Greaney MF. Truce–Smiles Rearrangements by Strain Release: Harnessing Primary Alkyl Radicals for Metal‐Free Arylation. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202108240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- David M. Whalley
- School of Chemistry The University of Manchester Oxford Road Manchester M13 9PL UK
- Institute of Chemical and Engineering Sciences 8 Biomedical Grove Neuros, #07-01 138665 Singapore
| | - Jayasree Seayad
- Institute of Chemical and Engineering Sciences 8 Biomedical Grove Neuros, #07-01 138665 Singapore
| | - Michael F. Greaney
- School of Chemistry The University of Manchester Oxford Road Manchester M13 9PL UK
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13
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Tlili A, Lakhdar S. Acridinium Salts and Cyanoarenes as Powerful Photocatalysts: Opportunities in Organic Synthesis. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202102262] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Anis Tlili
- Institute of Chemistry and Biochemistry (ICBMS-UMR CNRS 5246) Univ Lyon, Université Lyon 1 CNRS CPE-Lyon INSA 43 Bd du 11 Novembre 1918 69622 Villeurbanne France
| | - Sami Lakhdar
- CNRS/Université Toulouse III—Paul Sabatier Laboratoire Hétérochimie Fondamentale et Appliquée LHFA UMR 5069 118 Route de Narbonne 31062 Toulouse Cedex 09 France
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14
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Tlili A, Lakhdar S. Acridinium Salts and Cyanoarenes as Powerful Photocatalysts: Opportunities in Organic Synthesis. Angew Chem Int Ed Engl 2021; 60:19526-19549. [PMID: 33881207 DOI: 10.1002/anie.202102262] [Citation(s) in RCA: 83] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Revised: 04/16/2021] [Indexed: 01/18/2023]
Abstract
The use of organic photocatalysts has revolutionized the field of photoredox catalysis, as it allows access to reactivities that were traditionally restricted to transition-metal photocatalysts. This Minireview reports recent developments in the use of acridinium ions and cyanoarene derivatives in organic synthesis. The activation of inert chemical bonds as well as the late-stage functionalization of biorelevant molecules are discussed, with a special focus on their mechanistic aspects.
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Affiliation(s)
- Anis Tlili
- Institute of Chemistry and Biochemistry (ICBMS-UMR CNRS 5246), Univ Lyon, Université Lyon 1, CNRS, CPE-Lyon, INSA, 43 Bd du 11 Novembre 1918, 69622, Villeurbanne, France
| | - Sami Lakhdar
- CNRS/Université Toulouse III-Paul Sabatier, Laboratoire Hétérochimie Fondamentale et Appliquée, LHFA UMR 5069, 118 Route de Narbonne, 31062, Toulouse Cedex 09, France
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15
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Whalley DM, Seayad J, Greaney MF. Truce-Smiles Rearrangements by Strain Release: Harnessing Primary Alkyl Radicals for Metal-Free Arylation. Angew Chem Int Ed Engl 2021; 60:22219-22223. [PMID: 34370898 DOI: 10.1002/anie.202108240] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Indexed: 01/30/2023]
Abstract
The ring-opening of 3-aminocyclobutanone oximes enables easy generation of primary alkyl radicals, capable of undergoing an unprecedented strain-release, desulfonylative radical Truce-Smiles rearrangement, providing divergent access to valuable 1,3 diamines and unnatural β-amino acids. Characterized by mild conditions and wide scope of migrating species, this protocol allows the modular assembly of sp3 -aryls under transition metal-free, room-temperature conditions.
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Affiliation(s)
- David M Whalley
- School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.,Institute of Chemical and Engineering Sciences, 8 Biomedical Grove, Neuros, #07-01, 138665, Singapore
| | - Jayasree Seayad
- Institute of Chemical and Engineering Sciences, 8 Biomedical Grove, Neuros, #07-01, 138665, Singapore
| | - Michael F Greaney
- School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK
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Xu Q, Zhou X, Zhang S, Pan L, Liu Q, Li Y. Visible-Light-Induced Sulfur-Alkenylation of Alkenes. Org Lett 2021; 23:4870-4875. [PMID: 34109797 DOI: 10.1021/acs.orglett.1c01596] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
A visible-light-induced intermolecular sulfur-alkenylation of alkenes, including both activated and unactivated alkenes, is described. This sulfur-alkenylation reaction proceed in a highly regio- and stereospecific manner involving the visible-light-induced conversion of a ketene dithioacetal to the thiavinyl 1,3-dipole intermediate, followed by a formal [3 + 2] cycloaddition and C-S bond cleavage. Furthermore, it is also an efficient approach for the late-stage functionalization of natural products and complex molecules, even being induced by sunlight under ambient conditions.
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Affiliation(s)
- Qi Xu
- Jilin Province Key Laboratory of Organic Functional Molecular Design & Synthesis, Department of Chemistry, Northeast Normal University, Changchun 130024, China
| | - Xiaoxuan Zhou
- Jilin Province Key Laboratory of Organic Functional Molecular Design & Synthesis, Department of Chemistry, Northeast Normal University, Changchun 130024, China
| | - Si Zhang
- Jilin Province Key Laboratory of Organic Functional Molecular Design & Synthesis, Department of Chemistry, Northeast Normal University, Changchun 130024, China
| | - Ling Pan
- Jilin Province Key Laboratory of Organic Functional Molecular Design & Synthesis, Department of Chemistry, Northeast Normal University, Changchun 130024, China
| | - Qun Liu
- Jilin Province Key Laboratory of Organic Functional Molecular Design & Synthesis, Department of Chemistry, Northeast Normal University, Changchun 130024, China
| | - Yifei Li
- Jilin Province Key Laboratory of Organic Functional Molecular Design & Synthesis, Department of Chemistry, Northeast Normal University, Changchun 130024, China
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17
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Abrams R, Jesani MH, Browning A, Clayden J. Triarylmethanes and their Medium-Ring Analogues by Unactivated Truce-Smiles Rearrangement of Benzanilides. Angew Chem Int Ed Engl 2021; 60:11272-11277. [PMID: 33830592 PMCID: PMC8252078 DOI: 10.1002/anie.202102192] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 03/01/2021] [Indexed: 12/17/2022]
Abstract
Intramolecular nucleophilic aromatic substitution (Truce–Smiles rearrangement) of the anions of 2‐benzyl benzanilides leads to triarylmethanes in an operationally simple manner. The reaction succeeds even without electronic activation of the ring that plays the role of electrophile in the SNAr reaction, being accelerated instead by the preferred conformation imposed by the tertiary amide tether. The amide substituent of the product may be removed or transformed into alternative functional groups. A ring‐expanding variant (n to n+4) of the reaction provided a route to doubly benzo‐fused medium ring lactams of 10 or 11 members. Hammett analysis returned a ρ value consistent with the operation of a partially concerted reaction mechanism.
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Affiliation(s)
- Roman Abrams
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK
| | - Mehul H Jesani
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK
| | - Alex Browning
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK
| | - Jonathan Clayden
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK
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18
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Sharma S, Singh J, Sharma A. Visible Light Assisted Radical‐Polar/Polar‐Radical Crossover Reactions in Organic Synthesis. Adv Synth Catal 2021. [DOI: 10.1002/adsc.202100205] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Shivani Sharma
- Department of Chemistry Indian Institute of Technology Roorkee Roorkee 247667 India
| | - Jitender Singh
- Department of Chemistry Indian Institute of Technology Roorkee Roorkee 247667 India
| | - Anuj Sharma
- Department of Chemistry Indian Institute of Technology Roorkee Roorkee 247667 India
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19
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Abstract
We report the photosubstitution of one cyano group in dicyanobenzene-based photocatalysts and thermally activated delayed fluorescence (TADF) emitters. The reaction is a general degradation pathway for some widely used organic photocatalysts such as 4CzIPN and suggests that the active photocatalyst in many reactions is likely different from 4CzIPN. On the contrary, photosubstitution is a facile route to diverse highly reducing photocatalysts and blue TADF emitters.
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Affiliation(s)
- Sascha Grotjahn
- Faculty of Chemistry and Pharmacy, University of Regensburg, Universitaetsstrasse 31, 93053 Regensburg, Germany
| | - Burkhard König
- Faculty of Chemistry and Pharmacy, University of Regensburg, Universitaetsstrasse 31, 93053 Regensburg, Germany
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20
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Abrams R, Jesani MH, Browning A, Clayden J. Triarylmethanes and their Medium‐Ring Analogues by Unactivated Truce–Smiles Rearrangement of Benzanilides. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202102192] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Roman Abrams
- School of Chemistry University of Bristol, Cantock's Close Bristol BS8 1TS UK
| | - Mehul H. Jesani
- School of Chemistry University of Bristol, Cantock's Close Bristol BS8 1TS UK
| | - Alex Browning
- School of Chemistry University of Bristol, Cantock's Close Bristol BS8 1TS UK
| | - Jonathan Clayden
- School of Chemistry University of Bristol, Cantock's Close Bristol BS8 1TS UK
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21
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Asymmetric, visible light-mediated radical sulfinyl-Smiles rearrangement to access all-carbon quaternary stereocentres. Nat Chem 2021; 13:327-334. [DOI: 10.1038/s41557-021-00668-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 02/23/2021] [Indexed: 11/08/2022]
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22
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Yasui K, Kamitani M, Fujimoto H, Tobisu M. N-Heterocyclic Carbene-Catalyzed Truce-Smiles Rearrangement of N-Arylacrylamides via the Cleavage of Unactivated C(aryl)-N Bonds. Org Lett 2021; 23:1572-1576. [PMID: 33577343 DOI: 10.1021/acs.orglett.0c04281] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report on the N-heterocyclic carbene (NHC)-catalyzed Truce-Smiles rearrangement of aniline derivatives, in which an unactivated C(aryl)-N bond is cleaved, leading to the formation of a new C(aryl)-C bond. The key to the success of this reaction is the utilization of a highly nucleophilic NHC, which enables the formation of a highly nucleophilic ylide intermediate that is generated from an α,β-unsaturated amide.
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Affiliation(s)
- Kosuke Yasui
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Miharu Kamitani
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Hayato Fujimoto
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Mamoru Tobisu
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan.,Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, Suita, Osaka 565-0871, Japan
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23
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Radhoff N, Studer A. Functionalization of α-C(sp 3 )-H Bonds in Amides Using Radical Translocating Arylating Groups. Angew Chem Int Ed Engl 2021; 60:3561-3565. [PMID: 33215815 PMCID: PMC7898318 DOI: 10.1002/anie.202013275] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 11/19/2020] [Indexed: 01/09/2023]
Abstract
α-C-H arylation of N-alkylamides using 2-iodoarylsulfonyl radical translocating arylating (RTA) groups is reported. The method allows the construction of α-quaternary carbon centers in amides. Various mono- and disubstituted RTA-groups are applied to the arylation of primary, secondary, and tertiary α-C(sp3 )-H-bonds. These radical transformations proceed in good to excellent yields and the cascades comprise a 1,6-hydrogen atom transfer, followed by a 1,4-aryl migration with subsequent SO2 extrusion.
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Affiliation(s)
- Niklas Radhoff
- Organisch-Chemisches InstitutWestfälische Wilhelms-UniversitätCorrensstrasse 4048149MünsterGermany
| | - Armido Studer
- Organisch-Chemisches InstitutWestfälische Wilhelms-UniversitätCorrensstrasse 4048149MünsterGermany
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24
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Fehér PP. Density Functional Theory Evaluation of a Photoinduced Intramolecular Aryl Ether Rearrangement. J Org Chem 2021; 86:2706-2713. [PMID: 33412846 PMCID: PMC7880577 DOI: 10.1021/acs.joc.0c02706] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Recently, a new approach of converting
(hetero)aryl ethers to C–C
coupled products via a photoinduced intramolecular rearrangement has
been reported. Although this reaction is photocatalyst-free, it requires
excitation in the ultraviolet (UV) range. To help refine this process,
three different 2-(hetero)aryloxybenzaldehydes are selected from the
available substrate scope in which the general mechanism based on
experimental results is evaluated using density functional theory
calculations. The reaction takes place in the triplet state after
photoexcitation and includes three main steps: the addition of carbonyl
carbon to the ipso carbon of the aryl ether followed
by the C–O cleavage of the resulting spirocyclic intermediates
and then the transfer of the formyl proton to afford 2-hydroxybenzophenone-type
products. This agrees with the experiments, but the calculated pathways
show considerable differences between the three substrates. Above
all, either the first or the second step can be rate-determining but
not the C–H activation. The important factor behind the differences
is the spin-density rearrangement, which is mainly responsible for
the barrier of the ether cleavage. Based on the obtained insights,
the strategy to improve the ∼250 nm excitation has been briefly
discussed, and promising molecules are proposed to improve the scope
of this process.
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Affiliation(s)
- Péter Pál Fehér
- Research Centre for Natural Sciences, Magyar tudósok körútja 2, H-1117 Budapest, Hungary
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25
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Kleinmans R, Will LE, Schwarz JL, Glorius F. Photoredox-enabled 1,2-dialkylation of α-substituted acrylates via Ireland-Claisen rearrangement. Chem Sci 2021; 12:2816-2822. [PMID: 34164045 PMCID: PMC8179405 DOI: 10.1039/d0sc06385a] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Herein, we report the 1,2-dialkylation of simple feedstock acrylates for the synthesis of valuable tertiary carboxylic acids by merging Giese-type radical addition with an Ireland-Claisen rearrangement. Key to success is the utilization of the reductive radical-polar crossover concept under photocatalytic reaction conditions to force the [3,3]-sigmatropic rearrangement after alkyl radical addition to allyl acrylates. Using readily available alkyl boronic acids as radical progenitors, this redox-neutral, transition-metal-free protocol allows the mild formation of two C(sp3)-C(sp3) bonds, thus providing rapid access to complex tertiary carboxylic acids in a single step. Moreover, this strategy enables the efficient synthesis of highly attractive α,α-dialkylated γ-amino butyric acids (GABAs) when α-silyl amines are used as radical precursors - a structural motif that was still inaccessible in related transformations. Depending on the nature of the radical precursors and their inherent oxidation potentials, either a photoredox-induced radical chain or a solely photoredox mechanism is proposed to be operative.
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Affiliation(s)
- Roman Kleinmans
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster Corrensstraße 40 48149 Münster Germany
| | - Leon E Will
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster Corrensstraße 40 48149 Münster Germany
| | - J Luca Schwarz
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster Corrensstraße 40 48149 Münster Germany
| | - Frank Glorius
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster Corrensstraße 40 48149 Münster Germany
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26
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Donabauer K, König B. Strategies for the Photocatalytic Generation of Carbanion Equivalents for Reductant-Free C-C Bond Formations. Acc Chem Res 2021; 54:242-252. [PMID: 33325678 PMCID: PMC7871440 DOI: 10.1021/acs.accounts.0c00620] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Indexed: 12/18/2022]
Abstract
ConspectusThe use of photocatalysis in organic chemistry has encountered a surge of novel transformations since the start of the 21st century. The majority of these transformations are driven by the generation and subsequent reaction of radicals, owing to the intrinsic property of common photocatalysts to transfer single electrons from their excited state. While this is a powerful and elegant method to develop novel transformations, several research groups recently sought to further extend the toolbox of photocatalysis into the realm of polar ionic reactivity by the formation of cationic as well as anionic key reaction intermediates to furnish a desired product.Our group became especially interested in the photocatalytic formation of anionic carbon nucleophiles, as the overall transformation resembles classical organometallic reactions like Grignard, Barbier, and Reformatsky reactions, which are ubiquitous in organic synthesis with broad applications especially in the formation of valuable C-C bonds. Although these classical reactions are frequently applied, their use still bears certain disadvantages; one is the necessity of an (over)stoichiometric amount of a reducing metal. The reducing, low-valent, metal is solely applied to activate the starting material to form the organometallic carbanion synthon, while the final reaction product does generally not contain a metal species. Hence, a stoichiometric amount of metal salt is bound to be generated at the end of each reaction, diminishing the atom economy. The use of visible light as mild and traceless activation agent to drive chemical reactions can be a means to arrive at a more atom economic transformation, as a reducing metal source is avoided. Beyond this, the vast pool of photocatalytic activation methods offers the potential to employ easily available starting materials, as simple as unfunctionalized alkanes, to open novel and more facile retrosynthetic pathways. However, as mentioned above, photocatalysis is dominated by open-shell radical reactivity. With neutral radicals showing an intrinsically different reactivity than ionic species, novel strategies to form intermediates expressing a polar behavior need to be developed in order to achieve this goal.In the last couple of years, several methods toward this aim have been reported by our group and others. This Account aims to give an overview of the different existing strategies to photocatalytically form carbon centered anions or equivalents of those in order to form C-C bonds. As the main concept is to omit a stoichiometric reductant source (like a low-valent metal in classical organometallic reactions), only redox-neutral and reductant-free transformations were taken into closer consideration. We present selected examples of important strategies and try to illustrate the intentions and concepts behind the methods developed by our group and others.
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Affiliation(s)
- Karsten Donabauer
- Institute for Organic Chemistry, University of
Regensburg, Universitätsstraße 31, 93053 Regensburg,
Germany
| | - Burkhard König
- Institute for Organic Chemistry, University of
Regensburg, Universitätsstraße 31, 93053 Regensburg,
Germany
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27
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Bryden MA, Zysman-Colman E. Organic thermally activated delayed fluorescence (TADF) compounds used in photocatalysis. Chem Soc Rev 2021; 50:7587-7680. [PMID: 34002736 DOI: 10.1039/d1cs00198a] [Citation(s) in RCA: 124] [Impact Index Per Article: 41.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Organic compounds that show Thermally Activated Delayed Fluorescence (TADF) have become wildly popular as next-generation emitters in organic light emitting diodes (OLEDs). Since 2016, a subset of these have found increasing use as photocatalysts. This review comprehensively highlights their potential by documenting the diversity of the reactions where an organic TADF photocatalyst can be used in lieu of a noble metal complex photocatalyst. Beyond the small number of TADF photocatalysts that have been used to date, the analysis conducted within this review reveals the wider potential of organic donor-acceptor TADF compounds as photocatalysts. A discussion of the benefits of compounds showing TADF for photocatalysis is presented, which paints a picture of a very promising future for organic photocatalyst development.
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Affiliation(s)
- Megan Amy Bryden
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, UK.
| | - Eli Zysman-Colman
- Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, KY16 9ST, UK.
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28
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Huynh M, De Abreu M, Belmont P, Brachet E. Spotlight on Photoinduced Aryl Migration Reactions. Chemistry 2020; 27:3581-3607. [DOI: 10.1002/chem.202003507] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Indexed: 12/16/2022]
Affiliation(s)
- Marie Huynh
- UMR CNRS 8038 CiTCoM Université de Paris 4 avenue de l'Observatoire 75006 Paris France
| | - Maxime De Abreu
- UMR CNRS 8038 CiTCoM Université de Paris 4 avenue de l'Observatoire 75006 Paris France
| | - Philippe Belmont
- UMR CNRS 8038 CiTCoM Université de Paris 4 avenue de l'Observatoire 75006 Paris France
| | - Etienne Brachet
- UMR CNRS 8038 CiTCoM Université de Paris 4 avenue de l'Observatoire 75006 Paris France
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29
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Radhoff N, Studer A. Radikalische Funktionalisierung von α‐C(sp
3
)‐H‐Bindungen in Amiden durch Translokations‐induzierende arylierende Gruppen. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202013275] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Niklas Radhoff
- Organisch-Chemisches Institut Westfälische Wilhelms-Universität Corrensstraße 40 48149 Münster Deutschland
| | - Armido Studer
- Organisch-Chemisches Institut Westfälische Wilhelms-Universität Corrensstraße 40 48149 Münster Deutschland
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30
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Millward MJ, Ellis E, Ward JW, Clayden J. Hydantoin-bridged medium ring scaffolds by migratory insertion of urea-tethered nitrile anions into aromatic C-N bonds. Chem Sci 2020; 12:2091-2096. [PMID: 34163972 PMCID: PMC8179327 DOI: 10.1039/d0sc06188c] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Bicyclic or tricyclic nitrogen-containing heterocyclic scaffolds were constructed rapidly by intramolecular nucleophilic aromatic substitution of metallated nitriles tethered by a urea linkage to a series of electronically unactivated heterocyclic precursors. The substitution reaction constitutes a ring expansion, enabled by the conformationally constrained tether between the nitrile and the heterocycle. Attack of the metallated urea leaving group on the nitrile generates a hydantoin that bridges the polycyclic products. X-ray crystallography reveals ring-dependant strain within the hydantoin.
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Affiliation(s)
- Makenzie J Millward
- School of Chemistry, University of Bristol Cantock's Close Bristol BS8 1TS UK
| | - Emily Ellis
- School of Chemistry, University of Bristol Cantock's Close Bristol BS8 1TS UK
| | - John W Ward
- School of Chemistry, University of Bristol Cantock's Close Bristol BS8 1TS UK
| | - Jonathan Clayden
- School of Chemistry, University of Bristol Cantock's Close Bristol BS8 1TS UK
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