1
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Liu W, Tian Y. Observing C-N bond formation in plasma: a case study of benzene and dinitrogen coupling via an arylnitrenium ion intermediate. Phys Chem Chem Phys 2024; 26:18016-18020. [PMID: 38894641 DOI: 10.1039/d4cp01594k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Directly fixing dinitrogen into value-added organics is one of the core issues, and yet a long-standing challenge, in chemical synthesis. In earlier discrete studies, direct amination of benzene with N2 has been achieved via non-thermal plasma-liquid reaction. Nonetheless, the reaction mechanism thereof remains elusive and the amination product was non-selective primarily including aniline and diphenylamine. Herein, non-thermal plasma reaction in combination with on-line mass spectrometry was employed to probe the reaction pathway by on-line detection of the transient intermediate and the stable amination product. The long-lived atomic nitrogen ions N+(3P) as well as the arylnitrenium ions' intermediacy were shown to play a pivotal role in the amination process, and the product distribution was affected by an external hydrogen source and likely dependent on the competing hydrogen abstraction reaction and intersystem crossing of the initially generated triplet state arylnitrenium ions. The mechanistic investigation in this work has implications for plasma-based nitrogen conversion into organics, but also has broader relevance for understanding the C-N coupling by other means directly with N2.
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Affiliation(s)
- Wen Liu
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Shaanxi 710127, China.
| | - Yonghui Tian
- Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry and Materials Science, Northwest University, Shaanxi 710127, China.
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2
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Photochemical generation and characterization of the 5-endo-10,11-dihydrodibenzoazepine nitrenium ion. Photochem Photobiol Sci 2022; 21:1907-1914. [DOI: 10.1007/s43630-022-00267-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2021] [Accepted: 07/04/2022] [Indexed: 10/17/2022]
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3
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Wang W, Zheng X, Zhang L, Li S, Zhao Y, Wang X. Cyclic (Amino)(Aryl)Nitrenium Cations with Lewis Acidity Controlled by Remote Substituents. CHINESE J CHEM 2021. [DOI: 10.1002/cjoc.202100690] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Wenqing Wang
- College of Chemistry and Material Science, Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule‐Based Materials Anhui Normal University Wuhu Anhui 241002 China
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering Nanjing University Nanjing Jiangsu 210023 China
| | - Xin Zheng
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering Nanjing University Nanjing Jiangsu 210023 China
- College of Science Henan Agricultural University Zhengzhou Henan 450002 China
| | - Leran Zhang
- College of Chemistry and Material Science, Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule‐Based Materials Anhui Normal University Wuhu Anhui 241002 China
| | - Shunjie Li
- College of Chemistry and Material Science, Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule‐Based Materials Anhui Normal University Wuhu Anhui 241002 China
| | - Yue Zhao
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering Nanjing University Nanjing Jiangsu 210023 China
| | - Xinping Wang
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering Nanjing University Nanjing Jiangsu 210023 China
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4
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Kütt A, Jeschke G, Toom L, Nerut J, Reed CA. Reactivity of Diarylnitrenium Ions. Chemistry 2020; 26:8871-8874. [PMID: 32180268 DOI: 10.1002/chem.202000930] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2020] [Revised: 03/13/2020] [Indexed: 01/29/2023]
Abstract
Hydride abstraction from diarylamines with the trityl ion is explored in an attempt to generate a stable diarylnitrenium ion, Ar2 N+ . Sequential H-atom abstraction reactions ensue. The first H-atom abstraction leads to intensely colored aminium radical cations, Ar2 NH.+ , some of which are quite stable. However, most undergo a second H-atom abstraction leading to ammonium ions, Ar2 NH2 + . In the absence of a ready source of H-atoms, a unique self-abstraction reaction occurs when Ar=Me5 C6 , leading to a novel iminium radical cation, Ar=N.+ Ar, which decays via a second self H-atom abstraction reaction to give a stable iminium ion, Ar=N+ HAr. These products differ substantially from those derived via photochemically produced diarylnitrenium ions.
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Affiliation(s)
- Agnes Kütt
- Institute of Chemistry, University of Tartu, Ravila 14A, 50411, Tartu, Estonia.,Department of Chemistry, University of California, Riverside, CA, 92521, USA
| | - Gunnar Jeschke
- Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 2, CH-8093, Zurich, Switzerland
| | - Lauri Toom
- Institute of Chemistry, University of Tartu, Ravila 14A, 50411, Tartu, Estonia
| | - Jaak Nerut
- Institute of Chemistry, University of Tartu, Ravila 14A, 50411, Tartu, Estonia
| | - Christopher A Reed
- Department of Chemistry, University of California, Riverside, CA, 92521, USA
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5
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Qiu Y, Winter AH. Anomalous Electronic Properties of Iodous Materials: Application to High-Spin Reactive Intermediates and Conjugated Polymers. J Org Chem 2020; 85:4145-4152. [DOI: 10.1021/acs.joc.9b03289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yunfan Qiu
- Department of Chemistry, Iowa State University, 2101 Hach Hall, Ames, Iowa 50010, United States
| | - Arthur H. Winter
- Department of Chemistry, Iowa State University, 2101 Hach Hall, Ames, Iowa 50010, United States
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6
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Abbott BZ, Hoobler PR, Schaefer HF. Relatives of cyanomethylene: replacement of the divalent carbon by B -, N +, Al -, Si, P +, Ga -, Ge, and As . Phys Chem Chem Phys 2019; 21:26438-26452. [PMID: 31774089 DOI: 10.1039/c9cp05777c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The lowest lying singlet and triplet states of HBCN-, HCCN, HNCN+, HAlCN-, HSiCN, HPCN+, HGaCN-, HGeCN, and HAsCN+ were studied using the CCSDT(Q)/CBS//CCSD(T)/aug-cc-pVQZ level of theory. Periodic trends in geometries, singlet-triplet gaps, and barriers to linearity were established and analyzed. The first row increasingly favors the triplet state, with a singlet-triplet gap (ΔEST = Esinglet - Etriplet) of 3.5 kcal mol-1, 11.9 kcal mol-1, and 22.6 kcal mol-1, respectively, for HBCN-, HCCN, and HNCN+. The second row increasing favors the singlet state, with singlet-triplet gaps of -20.4 kcal mol-1 (HAlCN-), -26.6 kcal mol-1 (HSiCN), and -26.8 kcal mol-1 (HPCN+). The third row also favors the singlet state, with singlet-triplet gaps of -26.8 kcal mol-1 (HGaCN-), -33.5 kcal mol-1 (HGeCN), and -33.1 kcal mol-1 (HAsCN+). The HXCN species have larger absolute singlet-triplet energy gaps compared to their parent species XH2 except for the case of X = N+. The effect of the substitution of hydrogen with a cyano group was analyzed with isodesmic bond separation analysis and NBO.
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Affiliation(s)
- Boyi Z Abbott
- Center for Computational Quantum Chemistry, University of Georgia, 140 Cedar Street, Athens, Georgia 30602, USA.
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7
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Falvey DE. Discrete Existence of Singlet Nitrenium Ions Revisited: Computational Studies of Non-Aryl Nitrenium Ions and Their Rearrangements. ACS OMEGA 2018; 3:10418-10432. [PMID: 31459169 PMCID: PMC6645317 DOI: 10.1021/acsomega.8b01038] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Accepted: 08/08/2018] [Indexed: 06/10/2023]
Abstract
Nitrenium ion species are examined using computational methods (DFT, MP2, coupled-cluster, and a composite method, CBS-APNO) with a particular emphasis on nonaromatic species (i.e., those lacking an aromatic or heteroaromatic ring in direct conjugation with the formal nitrenium ion center.) The substitution of the N+ center with alkyl, alkoxy, vinyl, acyl, and sulfonyl, among others, was evaluated. For these species, three properties are considered. (1) The stability of the nitrenium ions to unimolecular isomerizations such as 1,2 alkyl or H shifts; to the extent that the singlet states could be characterized as discrete minima on the potential energy surface (PES), (2) the effect of the substituents on singlet-triplet energy splitting as well as (3) the relative stabilities of the nitrenium ions as defined by N-hydration enthalpies (RR'N+ + H2O → RR'NOH2 +). Nearly all simple alkyl and di-alkyl nitrenium ion singlet states are predicted to rearrange without detectable barriers, largely through 1,2 H or alkyl shifts. Methyl and N,N-dimethylnitrenium ion singlet states could be characterized as formal minima on the PES. However, these species show small or insignificant barriers to isomerization. Disubstituted nitrenium ions that include an alkyl group and a conjugating substituent such as alkoxyl, vinyl, or phenyl show meaningful barriers to isomerization and are thus predicted to possess nontrivial lifetimes in solution. Alkyl groups substantially stabilize the singlet state relative to the situation in the parent nitrenium ion NH2 + to the point where the two states are nearly degenerate. Other groups that interact with the nitrenium ion center decrease the ΔE st in the order formoyl < vinyl < phenyl < alkoxy ∼ sulfonyl < cyclopropyl ∼ cyclobutyl. The latter two substituents interact strongly with the (singlet) nitrenium ion center through the formation of a nonclassical bonding reminiscent of the bisected cyclopropylcarbinyl ion case for carbocations. When singlet-state stability is evaluated in the context of N-hydration enthalpies, it is found that the ordering is acyl < vinyl < alkoxyl < phenyl < cyclopropyl and cyclobutyl.
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Affiliation(s)
- Daniel E. Falvey
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
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8
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Shimizu D, Fujimoto K, Osuka A. Stable Diporphyrinylaminyl Radical and Nitrenium Ion. Angew Chem Int Ed Engl 2018; 57:9434-9438. [PMID: 29882340 DOI: 10.1002/anie.201805385] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Indexed: 11/10/2022]
Abstract
Nitrenium ions, isoelectronic nitrogen counterparts of carbenes, are important intermediates in various biological and chemical processes. Herein we describe the first synthesis and characterization of a stable nitrenium ion without resonance stabilization by adjoining amino groups. Namely, a stable salt of a diporphyrinylnitrenium ion was synthesized by stepwise oxidation of the corresponding diporphyrinylamine through a stable aminyl radical. The nitrenium ion exhibits characteristic features such as a singlet ground state, enhanced double-bond character of the central C-N bonds, no reactivity toward water and methanol, and negative solvatochromic behavior.
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Affiliation(s)
- Daiki Shimizu
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Keisuke Fujimoto
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Atsuhiro Osuka
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
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9
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Shimizu D, Fujimoto K, Osuka A. Stable Diporphyrinylaminyl Radical and Nitrenium Ion. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201805385] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Daiki Shimizu
- Department of Chemistry; Graduate School of Science; Kyoto University; Sakyo-ku Kyoto 606-8502 Japan
| | - Keisuke Fujimoto
- Department of Chemistry; Graduate School of Science; Kyoto University; Sakyo-ku Kyoto 606-8502 Japan
| | - Atsuhiro Osuka
- Department of Chemistry; Graduate School of Science; Kyoto University; Sakyo-ku Kyoto 606-8502 Japan
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10
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Yun Z, Cheng R, Sun J, Zhang-Negrerie D, Du Y. Iodobenzene Dichloride/Zinc Chloride-Mediated Synthesis of N
-Alkoxyindole-3-carbonitriles from 3-Alkoxyimino-2-arylalkylnitriles via Intramolecular Heterocyclization. Adv Synth Catal 2017. [DOI: 10.1002/adsc.201701111] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Zhongxiang Yun
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; School of Pharmaceutical Science and Technology; Tianjin University; Tianjin 300072 People's Republic of China
| | - Ran Cheng
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; School of Pharmaceutical Science and Technology; Tianjin University; Tianjin 300072 People's Republic of China
| | - Jiyun Sun
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; School of Pharmaceutical Science and Technology; Tianjin University; Tianjin 300072 People's Republic of China
| | - Daisy Zhang-Negrerie
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; School of Pharmaceutical Science and Technology; Tianjin University; Tianjin 300072 People's Republic of China
| | - Yunfei Du
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency; School of Pharmaceutical Science and Technology; Tianjin University; Tianjin 300072 People's Republic of China
- Collaborative Innovation Center of Chemical Science and Engineering (Tianjin); Tianjin 300072 People's Republic of China
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11
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Fischer LJ, Dutton AS, Winter AH. Anomalous effect of non-alternant hydrocarbons on carbocation and carbanion electronic configurations. Chem Sci 2017; 8:4231-4241. [PMID: 29719673 PMCID: PMC5902794 DOI: 10.1039/c7sc01047h] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 04/30/2017] [Indexed: 12/01/2022] Open
Abstract
Carbocations are widely viewed to be closed-shell singlet electrophiles. Here, computations show that azulenyl-substituted carbocations have triplet ground states. This triplet ground state for azulenyl carbocations stands in striking contrast to the isomeric naphthenyl carbocation, which is a normal closed-shell singlet with a large singlet-triplet gap. Furthermore, substitution of the azulenyl carbocation can substantially alter the energy gap between the different electronic configurations and can manipulate the ground state towards either the singlet or the triplet state depending on the nature and location of the substituent. A detailed investigation into the origin of this spin state reversal, including NICS calculations, structural effects, substitution patterns, orbital analysis, and detailed linear free-energy relationships allowed us to distill a set of principles that caused these azulenyl carbocations to have such low-lying diradical states. The fundamental origin of this effect mostly centers on singlet state destabilization from increasing antiaromatic character, in combination with a smaller, but important, Baird triplet state aromatic stabilization. We find that azulene is not unique, as extension of these principles allowed us to generate simple rules to predict an entire class of analogous non-alternant carbocation and carbanion structures with low-energy or ground state diradical states, including a purely hydrocarbon triplet cation with a large singlet-triplet gap of 8 kcal mol-1. Although these ions have innocuous-looking Lewis structures, these triplet diradical ions are likely to have substantially different reactivity and properties than typical closed-shell singlet ions.
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Affiliation(s)
- Logan J Fischer
- Department of Chemistry , Iowa State University , 1608 Gilman Hall , Ames , IA 50010 , USA .
| | - Andrew S Dutton
- Department of Chemistry , Iowa State University , 1608 Gilman Hall , Ames , IA 50010 , USA .
| | - Arthur H Winter
- Department of Chemistry , Iowa State University , 1608 Gilman Hall , Ames , IA 50010 , USA .
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12
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Albright TR, Winter AH. A Fine Line Separates Carbocations from Diradical Ions in Donor-Unconjugated Cations. J Am Chem Soc 2015; 137:3402-10. [DOI: 10.1021/jacs.5b00707] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Toshia R. Albright
- Department
of Chemistry, Iowa State University, Ames, Iowa 50011, United States
| | - Arthur H. Winter
- Department
of Chemistry, Iowa State University, Ames, Iowa 50011, United States
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13
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Falvey DE. Nitrenium ion analogues of nonclassical carbocations: cyclopropylnitrenium, allylnitrenium, and azetidenium ions and mechanisms for their interconversion. Org Lett 2015; 17:484-7. [PMID: 25611763 DOI: 10.1021/ol503488b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cyclopropylnitrenium 3S, allylnitreium 6S, and azetidenium (i.e., the nitrogen analogue of cyclobutylcarbenium) ions were examined using density functional theory and a complete basis set method. Similarly to the carbon analogues, the singlet states of these species have several local minima with nonclassical bonding. Structures characterized include 3S, an N analogue of the bisected cyclopropylcarbinyl cation, 11S, an N analogue of the bicyclobutonium ion, and 6S, an unsymmetric 2-azidinylcarbinyl cation.
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Affiliation(s)
- Daniel E Falvey
- Department of Chemistry and Biochemistry, University of Maryland , College Park, Maryland 20742, United States
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14
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Bercovici DA, Brewer M. Stereospecific Intramolecular C–H Amination of 1-Aza-2-azoniaallene Salts. J Am Chem Soc 2012; 134:9890-3. [PMID: 22680985 DOI: 10.1021/ja303054c] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Daniel A. Bercovici
- Department of Chemistry, The University
of Vermont,
82 University Place, Burlington, Vermont 05405, United States
| | - Matthias Brewer
- Department of Chemistry, The University
of Vermont,
82 University Place, Burlington, Vermont 05405, United States
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15
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Yan Q, Luo J, Zhang-Negrerie D, Li H, Qi X, Zhao K. Oxidative Cyclization of 2-Aryl-3-arylamino-2-alkenenitriles to N-Arylindole-3-carbonitriles Mediated by NXS/Zn(OAc)2. J Org Chem 2011; 76:8690-7. [DOI: 10.1021/jo2012187] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Qiao Yan
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, P. R. China
| | - Ji Luo
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, P. R. China
| | - Daisy Zhang-Negrerie
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, P. R. China
| | - Hui Li
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, P. R. China
| | - Xiuxiang Qi
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, P. R. China
| | - Kang Zhao
- Tianjin Key Laboratory for Modern Drug Delivery & High-Efficiency, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, P. R. China
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16
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Stokes BJ, Richert KJ, Driver TG. Examination of the mechanism of Rh(2)(II)-catalyzed carbazole formation using intramolecular competition experiments. J Org Chem 2009; 74:6442-51. [PMID: 19663433 PMCID: PMC2883892 DOI: 10.1021/jo901224k] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The use of a rhodium(II) carboxylate catalyst enables the mild and stereoselective formation of carbazoles from biaryl azides. Intramolecular competition experiments of triaryl azides suggested the source of the selectivity. A primary intramolecular kinetic isotope effect was not observed, and correlation of the product ratios with Hammett sigma(+) values produced a plot with two intersecting lines with opposite rho values. These data suggest that electronic donation by the biaryl pi-system accelerates the formation of rhodium nitrenoid and that C-N bond formation occurs through a 4pi-electron-5-atom electrocyclization.
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Affiliation(s)
- Benjamin J. Stokes
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois, 60607-7061
| | - Kathleen J. Richert
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois, 60607-7061
| | - Tom G. Driver
- Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois, 60607-7061
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17
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Winter AH, Gibson HH, Falvey DE. Carbazolyl nitrenium ion: electron configuration and antiaromaticity assessed by laser flash photolysis, trapping rate constants, product analysis, and computational studies. J Org Chem 2007; 72:8186-95. [PMID: 17892298 DOI: 10.1021/jo0708184] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Laser flash photolysis of 1-(carbazol-9-yl)-2,4,6-trimethylpyridinium tetrafluoroborate generates the carbazolyl nitrenium ion (tau = 333 ns, kobs = 3.0 x 106 M-1s-1) having absorption bands at 570 and 620 nm in CH3CN. The nitrenium ion is found to have reactivity comparable to structurally similar closed-shell diarylnitrenium ions, but spectroscopic evidence favors an open-shell singlet diradical assignment for the observed nitrenium ion. The carbazolyl nitrenium ion is also more reactive than diarylnitrenium ions as a likely result of antiaromatic character. Ab initio and hybrid DFT calculations were performed to address the degree of antiaromaticity in this and similar nitrenium ions through analysis of optimized geometries, nucleus independent chemical shifts, and isodesmic reactions.
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Affiliation(s)
- Arthur H Winter
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20740, USA
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18
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Winter AH, Falvey DE, Cramer CJ, Gherman BF. Benzylic Cations with Triplet Ground States: Computational Studies of Aryl Carbenium Ions, Silylenium Ions, Nitrenium Ions, and Oxenium Ions Substituted with Meta π Donors. J Am Chem Soc 2007; 129:10113-9. [PMID: 17655230 DOI: 10.1021/ja070143m] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Density functional theory (B3LYP/6-31G(d,p)) was used to predict the effect of meta substitution on aryl cationic (Ar-X+) species, including aryloxenium ions, arylsilylenium ions, arylnitrenium ions, and arylcarbenium ions. Multireference second-order perturbation theory (CASPT2) calculations were used to benchmark the quantitative accuracy of the DFT calculations for representative systems. Substituting the meta positions on these species with pi donors stabilizes a pi,pi* diradical state analogous to the well-known m-xylylene diradical. Notably, the 3,5-bis(N,N-dimethylamino)benzyl cation is predicted to have a triplet ground state by 1.9 kcal/mol by DFT and to have essentially degenerate singlet-triplet states at the CASPT2(10,9) level of theory. Adding electron-withdrawing CF3 groups to the exocyclic carbon of this meta-disubstituted benzyl cation further increases the predicted singlet-triplet gap in favor of the triplet. Other aryl cationic species substituted with strong pi electron-donating groups in the meta positions are predicted to have low-energy or ground-state triplet states. Systems analogous to the naphthaquinodimethane diradicals are also reported.
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Affiliation(s)
- Arthur H Winter
- Department of Chemistry & Biochemistry, University of Maryland, College Park Maryland 20742-2021, USA
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19
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Nguyen TM, Novak M. Synthesis and Decomposition of an Ester Derivative of the Procarcinogen and Promutagen, PhIP, 2-Amino-1-methyl-6-phenyl-1H-imidazo[4,5-b]pyridine: Unusual Nitrenium Ion Chemistry. J Org Chem 2007; 72:4698-706. [PMID: 17542636 DOI: 10.1021/jo070306p] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The food-derived heterocyclic amine (HCA) carcinogen 2-amino-1-methyl-6-phenyl-1H-imidazo[4,5-b]pyridine, PhIP, is often generated in the highest concentration of the HCAs formed during broiling and frying of meat and fish. Although it is considered to be an important contributor to human cancer risk from exposure to HCAs, the chemistry of PhIP metabolites that presumably react with DNA to initiate carcinogenesis has received only cursory attention. We have synthesized the ester derivative N-pivaloxy-2-amino-1-methyl-6-phenyl-1H-imidazo[4,5-b]pyridine, 1b, and investigated its chemistry in aqueous solution. Although 1b was too unstable to isolate, we could characterize it by NMR methods in DMF-d7, a solvent in which it is stable at -40 degrees C. It decomposed rapidly in aqueous solution, but its conjugate acid, 1bH+, is not reactive. The nitrenium ion, 2, was trapped by N(3)(-) to form the unusual tetrazole adduct, 16. In the absence of N3-, the expected hydration products of 2 were not detected, but the reduction product, 12, was detected. Although such products are often taken as evidence of triplet nitrenium ions, the efficient trapping of 2 by N(3)(-) indicates that it is a ground state singlet species. The product 12 appears to be generated by reduction of an initially formed hydration product of 2. An alternative addition-elimination mechanism for the formation of 12 does not fit the available kinetic data. The selectivity of 2, measured as kaz/ks, the ratio of the second-order rate constant for its reaction with N(3)(-) and the first-order rate constant for its reaction with the aqueous solvent, is (2.3 +/- 0.6) x 10(4) M(-1), a value that is in the middle of the range of k(az)/k(s) of 10-10(6) M(-1) observed for nitrenium ions derived from other HCAs. The mutagenicity of aromatic amines (AAs) and HCAs, measured as the log of histidine revertants per nanomole of amine, log m, in Salmonella typhimurium TA 98 and TA 100 correlates with log(k(az)/k(s)) for a wide variety of carbocyclic and heterocyclic amine mutagens including PhIP. Previously developed linear regression models for mutagenicity that include log(k(az)/k(s)) as an independent variable predict log m for PhIP with good accuracy in both TA 98 and TA 100. Quantitative carcinogenicity data are less strongly correlated with log(k(az)/k(s)), so prediction of the carcinogenicity of PhIP and other HCAs or AAs based primarily on log(k(az)/k(s)) is less successful.
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Affiliation(s)
- Thach-Mien Nguyen
- Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, USA
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Thomas SI, Falvey DE. N,N-Di(4-halophenyl)nitrenium ions: nucleophilic trapping, aromatic substitution, and hydrogen atom transfer. J Org Chem 2007; 72:4626-34. [PMID: 17536861 DOI: 10.1021/jo062578i] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reactive intermediates N,N-di(4-chlorophenyl)nitrenium ion and N,N-di(4-bromophenyl)nitrenium ion were generated through photolysis of the corresponding N-amino(2,4,6,-collidinium) ions. The behavior of these diarylnitrenium ions was characterized by laser flash photolysis, analysis of the stable photoproducts, and ab initio calculations with density functional theory. The latter predict these species to have singlet ground states. The halogenated diarylnitrenium ions are significantly longer lived than the unsubstituted diphenylnitrenium ion. Specifically, cyclization to form carbazole derivatives occurs negligibly, if at all, with the halogenated derivatives. They do, however, carry out most of the characteristic reactions of singlet arylnitrenium ions, including combining with nucleophiles on the aryl rings, adding to arenes, and accepting electrons from readily oxidized traps. Interestingly these species also abstract H atoms from 1,4-cyclohexadiene and various phenol derivatives. The implication of the latter process in relation to the computed singlet-triplet energy gaps of ca. -12.5 kcal/mol is discussed.
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Affiliation(s)
- Selina I Thomas
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
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Nitrenium Ions and Problem of Direct Electrophilic Amination of Aromatic Compounds. RUSSIAN JOURNAL OF ORGANIC CHEMISTRY 2005. [DOI: 10.1007/s11178-005-0193-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Havlas Z, Kývala M, Michl ¶ * J. Spin–orbit coupling in biradicals. 5. Zero-field splitting in triplet dimethylnitrenium, dimethylphosphenium and dimethylarsenium cations. Mol Phys 2005. [DOI: 10.1080/00268970412331319245] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Winter AH, Falvey DE, Cramer CJ. Effect of meta Electron-Donating Groups on the Electronic Structure of Substituted Phenyl Nitrenium Ions. J Am Chem Soc 2004; 126:9661-8. [PMID: 15291569 DOI: 10.1021/ja047677x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Density functional theory (UB3LYP/6-31G(d,p)) was used to determine substituent effects on the singlet-triplet-state energy gap for 21 meta-substituted phenylnitrenium ions. It was found that strongly electron-donating substituents stabilize the triplet state relative to the singlet state. With sufficiently strong meta electron donors (e.g., m,m'-diaminophenylnitrenium ion) the triplet is predicted to be the ground state. Analysis of equilibrium geometries, Kohn-Sham orbital distributions, and Mulliken spin densities for the triplet states of this series of nitrenium ions leads to the conclusion that there are two spatially distinct types of low-energy triplet states. Simple arylnitrenium ions such as phenylnitrenium ions as well as those having electron-withdrawing or weakly donating meta substituents have lowest-energy triplet states that are n,pi in nature. That is, one singly occupied molecular orbital is orthogonal to the plane of the phenyl ring and one is coplanar. These n,pi triplets are generally characterized by large ArNH bond angles (ca. 130-132 degrees ) and an NH bond that is perpendicular to the plane of the phenyl ring. In contrast, meta donor arylnitrenium ions have a lowest-energy triplet state best described as pi,pi. That is, both singly occupied molecular orbitals are orthogonal to the aromatic ring. Such pi,pi states are characterized by NH bonds that are coplanar with the phenyl ring and have ArNH bond angles that are more acute (ca. 110-111 degrees ). These triplet nitrenium ions have electronic structures analogous to those of meta-benzoquinodimethane derivatives.
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Affiliation(s)
- Arthur H Winter
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742-2021, USA
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Di Stefano M, Rosi M, Sgamellotti A, Negri F. Reactions of N+ ions with benzene: a theoretical study on the C6NH6+ potential energy surface. Chem Phys 2004. [DOI: 10.1016/j.chemphys.2004.04.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Facchini P, Grandinetti F. Concerning the reaction between singlet nitrenium ions and water: a computational investigation on competitive reaction paths. J Comput Chem 2003; 24:547-64. [PMID: 12632470 DOI: 10.1002/jcc.10182] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The reaction between singlet nitrenium ions XNH(+) (X = F and Cl) and H(2)O has been investigated by high-level of theory ab initio calculations. The geometries of the involved intermediates, transition structures, and dissociation products have been optimized at the MP2(full)/6-31G(d) level of theory, and accurate total energies have been obtained using the Gaussian-3 (G3) procedure. The reaction commences by the exothermic formation of the F-NH-OH(2) (+) and Cl-NH-OH(2) (+) intermediates, which are in turn able to undergo two distinct low-energy reaction paths, namely, the isomerization to the N-protonated isomers of the hydroxylamines F-NH-OH or Cl-NH-OH, and the eventual extrusion of HF or HCl. The competitive or alternative occurrence of these two processes strictly depends on the nature of the substituent X. In the reaction between FNH(+) and H(2)O, the energy gained in the formation of the complex F-NH-OH(2) (+) from the association between FNH(+) and H(2)O, 52.1 kcal mol(-1), is by far larger than the activation barrier for the loss of HF from F-NH-OH(2) (+), computed as 24.9 kcal mol(-1). In addition, the F-NH-OH(2) (+) intermediate requires 33.0 kcal mol(-1) to overcome the barrier for the isomerization to F-NH(2)-OH(+). Therefore, the reaction between FNH(+) and H(2)O is expected to occur practically exclusively by HF elimination with formation of the HN-OH(+) ionic product. On the other hand, for the reaction between ClNH(+) and H(2)O, it is not possible to get a definitive conclusion on the competitive or alternative occurrence of the two reaction paths. In fact, the transition structure involved in the elimination of HCl from Cl-NH-OH(2) (+) is only 3.4 kcal mol(-1) lower in energy than the transition structure for the isomerization of Cl-NH-OH(2) (+) to Cl-NH(2)-OH(+). In addition, the absolute values of the energy barriers of these two processes, 24.2 and 27.6 kcal mol(-1), respectively, are comparable with the energy gained in the formation of the complex Cl-NH-OH(2) (+) from the association between ClNH(+) and H(2)O, 24.0 kcal mol(-).1 Therefore, the ClNH(+) cation is predicted to react with water significantly slower than FNH(+).
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Affiliation(s)
- Paola Facchini
- Dipartimento di Scienze Ambientali and Istituto Nazionale di Fisica della Materia (INFM), Unità di Viterbo, Università della Tuscia, Largo dell' Università, 01100, Viterbo, Italy
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N-arylnitreniurn ions. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2001. [DOI: 10.1016/s0065-3160(01)36005-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
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McIlroy S, Moran RJ, Falvey DE. Photogenerated Nitrenium Ions: A Search for Triplet-State Reactivity in the Chemistry of the Diphenylnitrenium Ion. J Phys Chem A 2000. [DOI: 10.1021/jp002756q] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sean McIlroy
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742
| | - Ricardo J. Moran
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742
| | - Daniel E. Falvey
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742
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Singlet-triplet energy gaps in highly stabilized nitrenium ions: experimental and theoretical study of 1,3-dimethylbenzotriazolium Ion. Org Lett 2000; 2:2451-4. [PMID: 10956519 DOI: 10.1021/ol006106g] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The first experimental determination of a singlet-triplet energy gap (DeltaE(st)) for an organic nitrenium ion was made for 1, 3-dimethylbenzotriazolium ion 1. Laser flash photolysis was used to determine DeltaE(st) for this persistent nitrenium ion and a value of -66 +/- 3 kcal mol(-)(1) was obtained. DFT calculations show excellent agreement with the experiment.
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Sullivan MB, Cramer CJ. Quantum Chemical Analysis of Heteroarylnitrenium Ions and Mechanisms for Their Self-Destruction. J Am Chem Soc 2000. [DOI: 10.1021/ja0005486] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Michael B. Sullivan
- Contribution from the Department of Chemistry and Supercomputer Institute, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455-0431
| | - Christopher J. Cramer
- Contribution from the Department of Chemistry and Supercomputer Institute, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455-0431
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