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Pradhan S, Kweon J, Sahoo MK, Jung H, Heo J, Kim YB, Kim D, Park JW, Chang S. A Formal γ-C-H Functionalization of Carboxylic Acids Guided by Metal-Nitrenoids as an Unprecedented Mechanistic Motif. J Am Chem Soc 2023; 145:28251-28263. [PMID: 38100053 DOI: 10.1021/jacs.3c11628] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2023]
Abstract
Harnessing the key intermediates in metal-catalyzed reactions is one of the most essential strategies in the development of selective organic transformations. The nitrogen group transfer reactivity of metal-nitrenoids to ubiquitous C-H bonds allows for diverse C-N bond formation to furnish synthetically valuable aminated products. In this study, we present an unprecedented reactivity of iridium and ruthenium nitrenoids to generate remote carbocation intermediates, which subsequently undergo nucleophile incorporation, thus developing a formal γ-C-H functionalization of carboxylic acids. Mechanistic investigations elucidated a unique singlet metal-nitrenoid reactivity to initiate an abstraction of γ-hydride to form the carbocation intermediate that eventually reacts with a broad range of carbon, nitrogen, and oxygen nucleophiles, as well as biorelevant molecules. Alternatively, the same intermediate can lead to deprotonation to afford β,γ-unsaturated amides in a less nucleophilic solvent.
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Affiliation(s)
- Sourav Pradhan
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, South Korea
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Jeonguk Kweon
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, South Korea
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Manoj Kumar Sahoo
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, South Korea
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Hoimin Jung
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, South Korea
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Joon Heo
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, South Korea
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Yeong Bum Kim
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, South Korea
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Dongwook Kim
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, South Korea
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Jung-Woo Park
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, South Korea
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Sukbok Chang
- Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, South Korea
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
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2
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Meger FS, Murphy JA. Recent Advances in C-H Functionalisation through Indirect Hydrogen Atom Transfer. Molecules 2023; 28:6127. [PMID: 37630379 PMCID: PMC10459052 DOI: 10.3390/molecules28166127] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2023] [Revised: 08/09/2023] [Accepted: 08/15/2023] [Indexed: 08/27/2023] Open
Abstract
The functionalisation of C-H bonds has been an enormous achievement in synthetic methodology, enabling new retrosynthetic disconnections and affording simple synthetic equivalents for synthons. Hydrogen atom transfer (HAT) is a key method for forming alkyl radicals from C-H substrates. Classic reactions, including the Barton nitrite ester reaction and Hofmann-Löffler-Freytag reaction, among others, provided early examples of HAT. However, recent developments in photoredox catalysis and electrochemistry have made HAT a powerful synthetic tool capable of introducing a wide range of functional groups into C-H bonds. Moreover, greater mechanistic insights into HAT have stimulated the development of increasingly site-selective protocols. Site-selectivity can be achieved through the tuning of electron density at certain C-H bonds using additives, a judicious choice of HAT reagent, and a solvent system. Herein, we describe the latest methods for functionalizing C-H/Si-H/Ge-H bonds using indirect HAT between 2018-2023, as well as a critical discussion of new HAT reagents, mechanistic aspects, substrate scopes, and background contexts of the protocols.
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Affiliation(s)
- Filip S. Meger
- Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology, 16 Avinguda dels Països Catalans, 43007 Tarragona, Catalonia, Spain
| | - John A. Murphy
- Department of Pure and Applied Chemistry, University of Strathclyde, 295 Cathedral Street, Glasgow G1 1XL, UK
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3
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Nathanael JG, Yuan B, Wille U. Oxidative Damage of Aliphatic Amino Acid Residues by the Environmental Pollutant NO 3·: Impact of Water on the Reactivity. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:7687-7695. [PMID: 35671332 DOI: 10.1021/acs.est.2c00863] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The rate of oxidative damage of aliphatic amino acids and dipeptides by the environmental pollutant nitrate radical (NO3·) in an aqueous acidic environment was studied by laser flash photolysis. The reactivity dropped by a factor of about four for amino acid residues with secondary amide bonds and by a factor of up to nearly 20 for amino acid residues with tertiary amide bonds, compared with that in acetonitrile. According to density functional theory studies, the lower reactivity is due to protonation of the amide moiety, whereas in neutral water, hydrogen bonding with the amide should have little impact on the absolute reaction rate compared with that in acetonitrile. This finding can be rationalized by the high reactivity and broad reaction pattern of NO3·. Although hydrogen bonding involving the amide group raises the energies associated with some electron transfer processes, alternative low-energy pathways remain available so that the overall reaction rate is barely affected. The undiminished high reactivity of NO3· toward aliphatic amino acid residues in a neutral aqueous environment highlights the health-damaging potential of exposure to the combined air pollutants nitrogen dioxide (NO2·) and ozone (O3).
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Affiliation(s)
- Joses Grady Nathanael
- School of Chemistry, Bio21 Institute, The University of Melbourne, 30 Flemington Road, Parkville, Victoria 3010, Australia
| | - Bing Yuan
- School of Chemistry, Bio21 Institute, The University of Melbourne, 30 Flemington Road, Parkville, Victoria 3010, Australia
| | - Uta Wille
- School of Chemistry, Bio21 Institute, The University of Melbourne, 30 Flemington Road, Parkville, Victoria 3010, Australia
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4
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Zeplichal M, Gies J, Bernd J, Winslaws DK, Chang T, Chen YS, Strauss SH, Boltalina OV, Terfort A. Fluorinated Azaacenes: Efficient Syntheses, Structures, and Electrochemical Properties. J Fluor Chem 2022. [DOI: 10.1016/j.jfluchem.2022.109960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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5
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Capaldo L, Ravelli D, Fagnoni M. Direct Photocatalyzed Hydrogen Atom Transfer (HAT) for Aliphatic C-H Bonds Elaboration. Chem Rev 2021; 122:1875-1924. [PMID: 34355884 PMCID: PMC8796199 DOI: 10.1021/acs.chemrev.1c00263] [Citation(s) in RCA: 318] [Impact Index Per Article: 106.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
![]()
Direct photocatalyzed
hydrogen atom transfer (d-HAT) can be considered
a method of choice for the elaboration of
aliphatic C–H bonds. In this manifold, a photocatalyst (PCHAT) exploits the energy of a photon to trigger the homolytic
cleavage of such bonds in organic compounds. Selective C–H
bond elaboration may be achieved by a judicious choice of the hydrogen
abstractor (key parameters are the electronic character and the molecular
structure), as well as reaction additives. Different are the classes
of PCsHAT available, including aromatic ketones, xanthene
dyes (Eosin Y), polyoxometalates, uranyl salts, a metal-oxo porphyrin
and a tris(amino)cyclopropenium radical dication. The processes (mainly
C–C bond formation) are in most cases carried out under mild
conditions with the help of visible light. The aim of this review
is to offer a comprehensive survey of the synthetic applications of
photocatalyzed d-HAT.
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Affiliation(s)
- Luca Capaldo
- Flow Chemistry Group, Van't Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Davide Ravelli
- PhotoGreen Lab, Department of Chemistry, University of Pavia, Viale Taramelli 12, 27100 Pavia, Italy
| | - Maurizio Fagnoni
- PhotoGreen Lab, Department of Chemistry, University of Pavia, Viale Taramelli 12, 27100 Pavia, Italy
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6
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Cheng H, Chen C, Zhang R, Zhang JC, Zhang WY, He YQ, Gu YC. A Practical Approach for the Transamidation of N,N-Dimethyl Amides with Primary Amines Promoted by Sodium tert-Butoxide under Solvent-Free Conditions. SYNTHESIS-STUTTGART 2020. [DOI: 10.1055/s-0040-1705892] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
AbstractA practical sodium tert-butoxide (NaOtBu)-mediated protocol is disclosed for the transamidation of various N,N-dimethyl amides with primary amines to afford the corresponding amides in moderate to good yields at room temperature under solvent-free conditions. This protocol features a facile work-up procedure and good functional group compatibility, especially for N,N-dimethyl amides with long-chain alkyl groups and heteroatom-containing amines. Notably, a few representative gram-scale reactions proceed smoothly to furnish the desired amides in high yields, which demonstrates the potential of this process for further practical applications. Several control experiments are carried out and a plausible mechanism is provided.
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Affiliation(s)
- Hua Cheng
- Department of Chemical Engineering and Food Science
| | - Cheng Chen
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing
| | - Rui Zhang
- Department of Chemical Engineering and Food Science
| | | | - Wei-Yi Zhang
- Department of Chemical Engineering and Food Science
| | - Yu-Qing He
- Department of Chemical Engineering and Food Science
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7
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Copper-catalyzed sp3-carbon radical/carbamoyl radical cross coupling: A direct strategy for carbamoylation of 1,3-dicarbonyl compounds. Tetrahedron 2020. [DOI: 10.1016/j.tet.2020.131342] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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8
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Tan Z, Li Z, Ma Y, Qin J, Yu C. Potassium tert
-Butoxide Prompted Highly Efficient Transamidation and Its Coordination Radical Mechanism. European J Org Chem 2019. [DOI: 10.1002/ejoc.201900666] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Zhiyong Tan
- National Engineering Research Center for Process Development of Active Pharmaceutical Ingredients; Collaborative Innovation Center of Yangtze River Delta Region, Green Pharmaceuticals; Zhejiang University of Technology; 310014 Hangzhou P. R. China
| | - Zhenhua Li
- Key Laboratory for Green Pharmaceutical Technologies and Related Equipment of Ministry of Education; College of Pharmaceutical Sciences; Zhejiang University of Technology; 310014 Hangzhou P. R. China
| | - Yao Ma
- Key Laboratory for Green Pharmaceutical Technologies and Related Equipment of Ministry of Education; College of Pharmaceutical Sciences; Zhejiang University of Technology; 310014 Hangzhou P. R. China
| | - Jinjing Qin
- National Engineering Research Center for Process Development of Active Pharmaceutical Ingredients; Collaborative Innovation Center of Yangtze River Delta Region, Green Pharmaceuticals; Zhejiang University of Technology; 310014 Hangzhou P. R. China
| | - Chuanming Yu
- National Engineering Research Center for Process Development of Active Pharmaceutical Ingredients; Collaborative Innovation Center of Yangtze River Delta Region, Green Pharmaceuticals; Zhejiang University of Technology; 310014 Hangzhou P. R. China
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9
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Bietti M. Anwendung von Mediumeffekten in Aktivierungs‐ und Deaktivierungsstrategien zur selektiven Funktionalisierung aliphatischer C‐H‐Bindungen. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201804929] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Massimo Bietti
- Dipartimento di Scienze e Tecnologie ChimicheUniversità “Tor Vergata” Via della Ricerca Scientifica, 1 I-00133 Rome Italien
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10
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Bietti M. Activation and Deactivation Strategies Promoted by Medium Effects for Selective Aliphatic C-H Bond Functionalization. Angew Chem Int Ed Engl 2018; 57:16618-16637. [PMID: 29873935 DOI: 10.1002/anie.201804929] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 05/31/2018] [Indexed: 12/17/2022]
Abstract
Selective functionalization of unactivated aliphatic C-H bonds represents an important goal of modern synthetic chemistry. Differentiating between such bonds in organic molecules with high levels of selectivity remains a crucial issue, and a profound understanding of even the subtlest reactivity trends is needed. Among the methods that have been developed, those based on hydrogen atom transfer (HAT) have attracted considerable interest. Within this framework, medium effects have proved effective in altering the reactivity and site selectivity in synthetically useful C-H functionalization procedures. In this Review, the mechanistic features behind the available strategies are discussed. It is shown that hydrogen bonding and acid-base interactions can promote C-H bond activation or deactivation toward HAT reagents, thereby providing fine-control over the site selectivity and product chemoselectivity as well as useful guidelines for future development and applications.
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Affiliation(s)
- Massimo Bietti
- Dipartimento di Scienze e Tecnologie Chimiche, Università "Tor Vergata", Via della Ricerca Scientifica, 1, I-00133, Rome, Italy
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11
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Ottenbacher RV, Talsi EP, Rybalova TV, Bryliakov KP. Enantioselective Benzylic Hydroxylation of Arylalkanes with H
2
O
2
in Fluorinated Alcohols in the Presence of Chiral Mn Aminopyridine Complexes. ChemCatChem 2018. [DOI: 10.1002/cctc.201801476] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Roman V. Ottenbacher
- Novosibirsk State University Novosibirsk 630090 Russia
- Boreskov Institute of Catalysis Novosibirsk 630090 Russia
| | - Evgenii P. Talsi
- Novosibirsk State University Novosibirsk 630090 Russia
- Boreskov Institute of Catalysis Novosibirsk 630090 Russia
| | - Tatyana V. Rybalova
- Novosibirsk State University Novosibirsk 630090 Russia
- Vorozhtsov Novosibirsk Institute of Organic Chemistry Novosibirsk 630090 Russia
| | - Konstantin P. Bryliakov
- Novosibirsk State University Novosibirsk 630090 Russia
- Boreskov Institute of Catalysis Novosibirsk 630090 Russia
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12
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Dantignana V, Milan M, Cussó O, Company A, Bietti M, Costas M. Chemoselective Aliphatic C-H Bond Oxidation Enabled by Polarity Reversal. ACS CENTRAL SCIENCE 2017; 3:1350-1358. [PMID: 29296677 PMCID: PMC5746866 DOI: 10.1021/acscentsci.7b00532] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2017] [Indexed: 06/07/2023]
Abstract
Methods for selective oxidation of aliphatic C-H bonds are called on to revolutionize organic synthesis by providing novel and more efficient paths. Realization of this goal requires the discovery of mechanisms that can alter in a predictable manner the innate reactivity of these bonds. Ideally, these mechanisms need to make oxidation of aliphatic C-H bonds, which are recognized as relatively inert, compatible with the presence of electron rich functional groups that are highly susceptible to oxidation. Furthermore, predictable modification of the relative reactivity of different C-H bonds within a molecule would enable rapid diversification of the resulting oxidation products. Herein we show that by engaging in hydrogen bonding, fluorinated alcohols exert a polarity reversal on electron rich functional groups, directing iron and manganese catalyzed oxidation toward a priori stronger and unactivated C-H bonds. As a result, selective hydroxylation of methylenic sites in hydrocarbons and remote aliphatic C-H oxidation of otherwise sensitive alcohol, ether, amide, and amine substrates is achieved employing aqueous hydrogen peroxide as oxidant. Oxidations occur in a predictable manner, with outstanding levels of product chemoselectivity, preserving the first-formed hydroxylation product, thus representing an extremely valuable tool for synthetic planning and development.
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Affiliation(s)
- Valeria Dantignana
- Grup
de Química Bioinspirada, Supramolecular i Catàlisi (QBIS-CAT),
Institut de Química Computacional i Catàlisi (IQCC)
and Departament de Química, Universitat
de Girona, Campus Montilivi, Girona E-17071, Catalonia, Spain
| | - Michela Milan
- Grup
de Química Bioinspirada, Supramolecular i Catàlisi (QBIS-CAT),
Institut de Química Computacional i Catàlisi (IQCC)
and Departament de Química, Universitat
de Girona, Campus Montilivi, Girona E-17071, Catalonia, Spain
| | - Olaf Cussó
- Grup
de Química Bioinspirada, Supramolecular i Catàlisi (QBIS-CAT),
Institut de Química Computacional i Catàlisi (IQCC)
and Departament de Química, Universitat
de Girona, Campus Montilivi, Girona E-17071, Catalonia, Spain
| | - Anna Company
- Grup
de Química Bioinspirada, Supramolecular i Catàlisi (QBIS-CAT),
Institut de Química Computacional i Catàlisi (IQCC)
and Departament de Química, Universitat
de Girona, Campus Montilivi, Girona E-17071, Catalonia, Spain
| | - Massimo Bietti
- Dipartimento
di Scienze e Tecnologie Chimiche, Università
“Tor Vergata”, Via della Ricerca Scientifica, 1, I-00133 Rome, Italy
| | - Miquel Costas
- Grup
de Química Bioinspirada, Supramolecular i Catàlisi (QBIS-CAT),
Institut de Química Computacional i Catàlisi (IQCC)
and Departament de Química, Universitat
de Girona, Campus Montilivi, Girona E-17071, Catalonia, Spain
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13
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Li X. 2-Phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-Oxide (PTIO •) Radical Scavenging: A New and Simple Antioxidant Assay In Vitro. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2017; 65:6288-6297. [PMID: 28689421 DOI: 10.1021/acs.jafc.7b02247] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Current in vitro antioxidant assays have several limitations, which frequently cause inconsistent results. The study develops a new antioxidant assay using the 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide radical (PTIO•). After the investigation of various factors, the experimental protocol was briefly recommended as follows: PTIO• and the sample solution were added to phosphate buffer (pH 7.4, 50 mM), incubated at 37 °C for 2 h, and then spectrophotometrically measured at 557 nm. The validation test based on 20 pure compounds and 30 lyophilized aqueous extracts suggested that PTIO• scavenging had a good linear relationship, stability, and reproducibility. In the ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry analysis, PTIO• was observed to give m/z 234 when encountering l-ascorbic acid. As an antioxidant assay, PTIO• scavenging possesses four advantages, i.e., oxygen-centered radical, physiological aqueous solution, simple and direct measurement, and less interference from the tested sample. It can also satisfactorily analyze the antioxidant structure-activity relationship. PTIO• scavenging has no stereospecificity and is at least involved in H+ transfer.
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Affiliation(s)
- Xican Li
- School of Chinese Herbal Medicine and Innovative Research and Development Laboratory of TCM, Guangzhou University of Chinese Medicine , 232 Waihuan East Road, Guangzhou Higher Education Mega Center, Panyu District, Guangzhou, Guangdong 510006, People's Republic of China
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14
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Bietti M, Forcina V, Lanzalunga O, Lapi A, Martin T, Mazzonna M, Salamone M. Kinetic Study of the Reaction of the Phthalimide-N-oxyl Radical with Amides: Structural and Medium Effects on the Hydrogen Atom Transfer Reactivity and Selectivity. J Org Chem 2016; 81:11924-11931. [PMID: 27934460 DOI: 10.1021/acs.joc.6b02482] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A kinetic study of the hydrogen atom transfer (HAT) reactions from a series of secondary N-(4-X-benzyl)acetamides and tertiary amides to the phthalimide-N-oxyl radical (PINO) has been carried out. The results indicate that HAT is strongly influenced by structural and medium effects; in particular, the addition of Brønsted and Lewis acids determines a significant deactivation of C-H bonds α to the amide nitrogen of these substrates. Thus, by changing the reaction medium, it is possible to carefully control the regioselectivity of the aerobic oxidation of amides catalyzed by N-hydroxyphthalimide, widening the synthetic versatility of this process.
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Affiliation(s)
- Massimo Bietti
- Dipartimento di Scienze e Tecnologie Chimiche, Università "Tor Vergata″ , Via della Ricerca Scientifica 1, I-00133 Rome, Italy
| | - Veronica Forcina
- Dipartimento di Chimica, Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche (IMC-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Sapienza Università di Roma , Piazzale Aldo Moro 5, I-00185 Rome, Italy
| | - Osvaldo Lanzalunga
- Dipartimento di Chimica, Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche (IMC-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Sapienza Università di Roma , Piazzale Aldo Moro 5, I-00185 Rome, Italy
| | - Andrea Lapi
- Dipartimento di Chimica, Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche (IMC-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Sapienza Università di Roma , Piazzale Aldo Moro 5, I-00185 Rome, Italy
| | - Teo Martin
- Dipartimento di Chimica, Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche (IMC-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Sapienza Università di Roma , Piazzale Aldo Moro 5, I-00185 Rome, Italy
| | - Marco Mazzonna
- Dipartimento di Chimica, Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche (IMC-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Sapienza Università di Roma , Piazzale Aldo Moro 5, I-00185 Rome, Italy
| | - Michela Salamone
- Dipartimento di Scienze e Tecnologie Chimiche, Università "Tor Vergata″ , Via della Ricerca Scientifica 1, I-00133 Rome, Italy
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15
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Li YB, Liu F, Luo HY, Zhu YF, Liang XF, Liu HZ, Zhong JJ. Hydrolytic kinetics of piceid and its importance for the production of resveratrol. Process Biochem 2016. [DOI: 10.1016/j.procbio.2016.06.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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16
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Yao SG, Meier MS, Pace III RB, Crocker M. A comparison of the oxidation of lignin model compounds in conventional and ionic liquid solvents and application to the oxidation of lignin. RSC Adv 2016. [DOI: 10.1039/c6ra18806k] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The oxidation of lignin model compounds in ionic liquid solvents was investigated as a prelude to the oxidation of lignin in these solvents where the polymer is appreciably soluble.
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Affiliation(s)
- Soledad G. Yao
- Department of Chemistry
- University of Kentucky
- Lexington
- USA
| | - Mark S. Meier
- Department of Chemistry
- University of Kentucky
- Lexington
- USA
| | | | - Mark Crocker
- Department of Chemistry
- University of Kentucky
- Lexington
- USA
- Center for Applied Energy Research
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17
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Salamone M, Bietti M. Tuning reactivity and selectivity in hydrogen atom transfer from aliphatic C-H bonds to alkoxyl radicals: role of structural and medium effects. Acc Chem Res 2015; 48:2895-903. [PMID: 26545103 DOI: 10.1021/acs.accounts.5b00348] [Citation(s) in RCA: 157] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Hydrogen atom transfer (HAT) is a fundamental reaction that takes part in a wide variety of chemical and biological processes, with relevant examples that include the action of antioxidants, damage to biomolecules and polymers, and enzymatic and biomimetic reactions. Moreover, great attention is currently devoted to the selective functionalization of unactivated aliphatic C-H bonds, where HAT based procedures have been shown to play an important role. In this Account, we describe the results of our recent studies on the role of structural and medium effects on HAT from aliphatic C-H bonds to the cumyloxyl radical (CumO(•)). Quantitative information on the reactivity and selectivity patterns observed in these reactions has been obtained by time-resolved kinetic studies, providing a deeper understanding of the factors that govern HAT from carbon and leading to the definition of useful guidelines for the activation or deactivation of aliphatic C-H bonds toward HAT. In keeping with the electrophilic character of alkoxyl radicals, polar effects can play an important role in the reactions of CumO(•). Electron-rich C-H bonds are activated whereas those that are α to electron withdrawing groups are deactivated toward HAT, with these effects being able to override the thermodynamic preference for HAT from the weakest C-H bond. Stereoelectronic effects can also influence the reactivity of the C-H bonds of ethers, amines, and amides. HAT is most rapid when these bonds can be eclipsed with a lone pair on an adjacent heteroatom or with the π-system of an amide functionality, thus allowing for optimal orbital overlap. In HAT from cyclohexane derivatives, tertiary axial C-H bond deactivation and tertiary equatorial C-H bond activation have been observed. These effects have been explained on the basis of an increase in torsional strain or a release in 1,3-diaxial strain in the HAT transition states, with kH(eq)/kH(ax) ratios that have been shown to exceed one order of magnitude. Medium effects on HAT from aliphatic C-H bonds to CumO(•) have been also investigated. With basic substrates, from large to very large decreases in kH have been measured with increasing solvent hydrogen bond donor (HBD) ability or after addition of protic acids or alkali and alkaline earth metal ions, with kinetic effects that exceed 2 orders of magnitude in the reactions of tertiary alkylamines and alkanamides. Solvent hydrogen bonding, protonation, and metal ion binding increase the electron deficiency and the strength of the C-H bonds of these substrates deactivating these bonds toward HAT, with the extent of this deactivation being modulated by varying the nature of the substrate, solvent, protic acid, and metal ion. These results indicate that through these interactions careful control over the HAT reactivity of basic substrates toward CumO(•) and other electrophilic radicals can be achieved, suggesting moreover that these effects can be exploited in an orthogonal fashion for selective C-H bond functionalization of substrates bearing different basic functionalities.
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Affiliation(s)
- Michela Salamone
- Dipartimento
di Scienze e
Tecnologie Chimiche, Università “Tor Vergata”, Via
della Ricerca Scientifica, 1, I-00133 Rome, Italy
| | - Massimo Bietti
- Dipartimento
di Scienze e
Tecnologie Chimiche, Università “Tor Vergata”, Via
della Ricerca Scientifica, 1, I-00133 Rome, Italy
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Salamone M, Carboni G, Mangiacapra L, Bietti M. Binding to Redox-Inactive Alkali and Alkaline Earth Metal Ions Strongly Deactivates the C–H Bonds of Tertiary Amides toward Hydrogen Atom Transfer to Reactive Oxygen Centered Radicals. J Org Chem 2015; 80:9214-23. [DOI: 10.1021/acs.joc.5b01661] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Michela Salamone
- Dipartimento
di Scienze e
Tecnologie Chimiche, Università “Tor Vergata”, Via
della Ricerca Scientifica, 1, I-00133 Rome, Italy
| | - Giulia Carboni
- Dipartimento
di Scienze e
Tecnologie Chimiche, Università “Tor Vergata”, Via
della Ricerca Scientifica, 1, I-00133 Rome, Italy
| | - Livia Mangiacapra
- Dipartimento
di Scienze e
Tecnologie Chimiche, Università “Tor Vergata”, Via
della Ricerca Scientifica, 1, I-00133 Rome, Italy
| | - Massimo Bietti
- Dipartimento
di Scienze e
Tecnologie Chimiche, Università “Tor Vergata”, Via
della Ricerca Scientifica, 1, I-00133 Rome, Italy
| |
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