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Alabugin IV, Kuhn L, Medvedev MG, Krivoshchapov NV, Vil' VA, Yaremenko IA, Mehaffy P, Yarie M, Terent'ev AO, Zolfigol MA. Stereoelectronic power of oxygen in control of chemical reactivity: the anomeric effect is not alone. Chem Soc Rev 2021; 50:10253-10345. [PMID: 34263287 DOI: 10.1039/d1cs00386k] [Citation(s) in RCA: 66] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Although carbon is the central element of organic chemistry, oxygen is the central element of stereoelectronic control in organic chemistry. Generally, a molecule with a C-O bond has both a strong donor (a lone pair) and a strong acceptor (e.g., a σ*C-O orbital), a combination that provides opportunities to influence chemical transformations at both ends of the electron demand spectrum. Oxygen is a stereoelectronic chameleon that adapts to the varying situations in radical, cationic, anionic, and metal-mediated transformations. Arguably, the most historically important stereoelectronic effect is the anomeric effect (AE), i.e., the axial preference of acceptor groups at the anomeric position of sugars. Although AE is generally attributed to hyperconjugative interactions of σ-acceptors with a lone pair at oxygen (negative hyperconjugation), recent literature reports suggested alternative explanations. In this context, it is timely to evaluate the fundamental connections between the AE and a broad variety of O-functional groups. Such connections illustrate the general role of hyperconjugation with oxygen lone pairs in reactivity. Lessons from the AE can be used as the conceptual framework for organizing disjointed observations into a logical body of knowledge. In contrast, neglect of hyperconjugation can be deeply misleading as it removes the stereoelectronic cornerstone on which, as we show in this review, the chemistry of organic oxygen functionalities is largely based. As negative hyperconjugation releases the "underutilized" stereoelectronic power of unshared electrons (the lone pairs) for the stabilization of a developing positive charge, the role of orbital interactions increases when the electronic demand is high and molecules distort from their equilibrium geometries. From this perspective, hyperconjugative anomeric interactions play a unique role in guiding reaction design. In this manuscript, we discuss the reactivity of organic O-functionalities, outline variations in the possible hyperconjugative patterns, and showcase the vast implications of AE for the structure and reactivity. On our journey through a variety of O-containing organic functional groups, from textbook to exotic, we will illustrate how this knowledge can predict chemical reactivity and unlock new useful synthetic transformations.
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Affiliation(s)
- Igor V Alabugin
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, USA.
| | - Leah Kuhn
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, USA.
| | - Michael G Medvedev
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russian Federation.,A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 28 Vavilova St., 119991 Moscow, Russian Federation
| | - Nikolai V Krivoshchapov
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russian Federation.,Lomonosov Moscow State University, Leninskie Gory 1 (3), Moscow, 119991, Russian Federation
| | - Vera A Vil'
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russian Federation
| | - Ivan A Yaremenko
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russian Federation
| | - Patricia Mehaffy
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, USA.
| | - Meysam Yarie
- Department of Organic Chemistry, Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65167, Iran
| | - Alexander O Terent'ev
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russian Federation
| | - Mohammad Ali Zolfigol
- Department of Organic Chemistry, Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65167, Iran
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Buschbeck-Alvarado ME, Hernández-Fernández G, Hernández-Trujillo J, Cortés-Guzmán F, Cuevas G. Charge transfer and electron localization as the origin of the anomeric effect in the O─C─O segment of dimethoxymethane and spiroketals. J PHYS ORG CHEM 2017. [DOI: 10.1002/poc.3793] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
| | | | | | | | - Gabriel Cuevas
- Instituto de Química; Universidad Nacional Autónoma de México; Ciudad de México Mexico
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Affiliation(s)
- Charles L. Perrin
- Department of Chemistry & Biochemistry University of California, San Diego, La Jolla, California 92093-0358, United States
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Garcias-Morales C, Ortegón-Reyna D, Ariza-Castolo A. Investigation of the role of stereoelectronic effects in the conformation of piperidones by NMR spectroscopy and X-ray diffraction. Beilstein J Org Chem 2015; 11:1973-84. [PMID: 26664617 PMCID: PMC4660988 DOI: 10.3762/bjoc.11.213] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 10/01/2015] [Indexed: 12/28/2022] Open
Abstract
This paper reports the synthesis of a series of piperidones 1-8 by the Mannich reaction and analysis of their structures and conformations in solution by NMR and mass spectrometry. The six-membered rings in 2,4,6,8-tetraphenyl-3,7-diazabicyclo[3.3.1]nonan-9-ones, compounds 1 and 2, adopt a chair-boat conformation, while those in 2,4-diphenyl-3-azabicyclo[3.3.1]nonan-9-ones, compounds 3-8, adopt a chair-chair conformation because of stereoelectronic effects. These stereoelectronic effects were analyzed by the (1) J C-H coupling constants, which were measured in the (13)C satellites of the (1)H NMR spectra obtained with the hetero-dqf pulse sequence. In the solid state, these stereoelectronic effects were investigated by measurement of X-ray diffraction data, the molecular geometry (torsional bond angles and bond distances), and inter- and intramolecular interactions, and by natural bond orbital analysis, which was performed using density functional theory at the ωB97XD/6311++G(d,p) level. We found that one of the main factors influencing the conformational stability of 3-8 is the interaction between the lone-pair electrons of nitrogen and the antibonding sigma orbital of C(7)-Heq (nN→σ*C-H(7)eq), a type of hyperconjugative interaction.
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Affiliation(s)
- Cesar Garcias-Morales
- Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Avenida Instituto Politécnico Nacional 2508 Colonia San Pedro Zacatenco, C.P. 07360, México, D.F., Mexico
| | - David Ortegón-Reyna
- Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Avenida Instituto Politécnico Nacional 2508 Colonia San Pedro Zacatenco, C.P. 07360, México, D.F., Mexico
| | - Armando Ariza-Castolo
- Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Avenida Instituto Politécnico Nacional 2508 Colonia San Pedro Zacatenco, C.P. 07360, México, D.F., Mexico
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Filloux CM. Das Problem der Ursachen und die Ursachen des Problems: Der Einfluss von Sprache auf Studien des anomeren Effekts. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201411185] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Filloux CM. The Problem of Origins and Origins of the Problem: Influence of Language on Studies Concerning the Anomeric Effect. Angew Chem Int Ed Engl 2015; 54:8880-94. [PMID: 26119827 DOI: 10.1002/anie.201411185] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 01/29/2015] [Indexed: 11/08/2022]
Abstract
Cause and effect: In science, language is often subordinated to empirical data, but words can influence our ability to understand and communicate science. This Essay argues that imprecise language has confounded studies that probe the interactions underlying the anomeric effect and related phenomena.
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Affiliation(s)
- Claire M Filloux
- Chemistry, Colorado State University, 1872 Campus Delivery, Fort Collins, CO 80523 (USA).
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Lazareva NF, Lazarev IM. Electronic effects of 2-azasilatran-3-one groups. RUSS J GEN CHEM+ 2013. [DOI: 10.1134/s1070363213090041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Masnabadi N, Manesh AT, Azarakhshi F. Ab Initio Calculations of the Conformational Preferences of 1,3-Oxathiane S-Oxide and its Analogs Containing Sand SEAtoms—Evidence for Stereoelectronic Interactions Associated with the Anomeric Effects. PHOSPHORUS SULFUR 2013. [DOI: 10.1080/10426507.2012.736098] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Nasrin Masnabadi
- a Department of Chemistry, Roudehen Branch , Islamic Azad University , Roudehen , Iran
| | - Afshin Taghva Manesh
- b Department of Chemistry, Tehran Central Branch , Islamic Azad University , Tehran , Iran
| | - Fatemeh Azarakhshi
- c Department of Chemistry, Varamin Branch , Islamic Azad University , Varamin , Iran
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Pan XL, Zhou YX, Liu W, Liu JY, Dong H. Stereoelectronic control of cleavage of dioxolane five-membered ring on carbohydrates. Chem Res Chin Univ 2013. [DOI: 10.1007/s40242-013-2293-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Garcías-Morales C, Martínez-Salas SH, Ariza-Castolo A. The effect of the nitrogen non-bonding electron pair on the NMR and X-ray in 1,3-diazaheterocycles. Tetrahedron Lett 2012. [DOI: 10.1016/j.tetlet.2012.04.077] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Dong H, Zhou Y, Pan X, Cui F, Liu W, Liu J, Ramström O. Stereoelectronic Control in Regioselective Carbohydrate Protection. J Org Chem 2012; 77:1457-67. [DOI: 10.1021/jo202336y] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hai Dong
- School of Chemistry & Chemical Engineering, Huazhong University of Science & Technology, Luoyu Road 1037, 430074, Wuhan, P. R. China
| | - Yixuan Zhou
- School of Chemistry & Chemical Engineering, Huazhong University of Science & Technology, Luoyu Road 1037, 430074, Wuhan, P. R. China
| | - Xiaoliang Pan
- Institute of Theoretical Chemistry,
State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Liutiao Road 2, 130023, Changchun,
P. R. China
| | - Fengchao Cui
- Institute of Theoretical Chemistry,
State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Liutiao Road 2, 130023, Changchun,
P. R. China
| | - Wei Liu
- Institute of Theoretical Chemistry,
State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Liutiao Road 2, 130023, Changchun,
P. R. China
| | - Jingyao Liu
- Institute of Theoretical Chemistry,
State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Liutiao Road 2, 130023, Changchun,
P. R. China
| | - Olof Ramström
- Department of
Chemistry, Royal Institute of Technology (KTH), Teknikringen 30,
S-10044, Stockholm, Sweden
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Cortés-Guzmán F, Hernández-Trujillo J, Cuevas G. Application of the additivity of group energies to understand conformational preference: the anomeric effect. Phys Chem Chem Phys 2010; 12:13261-5. [DOI: 10.1039/c002136a] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Barquera-Lozada JE, Cuevas G. Biogenesis of sesquiterpene lactones pseudoguaianolides from germacranolides: theoretical study on the reaction mechanism of terminal biogenesis of 8-epiconfertin. J Org Chem 2009; 74:874-83. [PMID: 19055363 DOI: 10.1021/jo802445n] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The fundamental study of the biogenetic origin of natural products has always been limited from the experimental point of view because proposed reaction mechanisms have only been supported on the molecular structures of reagents and the reaction products. In a seminal contribution, Ortega and Maldonado (Ortega, A.; Maldonado, E. Heterocycles, 1989, 29, 635-638.) described an experiment relevant for the development of the biogenetic theory of sesquiterpene lactones. They were able to obtain the one-pot transformation of a pseudoguaianolide sesquiterpenic lactone from a germacranolide using bentonitic earth as the catalyst. This transformation involved two steps in the biogenesis of these compounds (germacranolide --> guaianolide --> pseudoguaianolide) and is significant because when Brönsted or Lewis acids are used, it is only possible to isolate the product of the next step of the biogenesis. The results presented here support the biogenetic theories by Hendrickson and Fischer and question the concerted nature of the Herz proposal. Some questions about the mechanisms still remain unanswered; mainly because it was only possible to isolate a few stable byproducts. Using the third generation functional mPWB95 developed by Truhlar, it was possible to study the mechanisms associated with the biogenesis of pseudoguaiananolides. Its application can explain the origin of all the byproducts obtained in the original experiment and establish the validity of the original biogenetic hypothesis. The performance of the above-mentioned functional was compared to B3LYP, B97-2, and B1B95 functionals and the MP2 method, finding that mPWB95 competes successfully with all the latter in both, the determination of the magnitude of the activation energies and the ability to map the potential energy surface. Therefore, the mPWB95 method can be considered good to deal with this type of study.
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Affiliation(s)
- José Enrique Barquera-Lozada
- Instituto de Quimica, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70213, 04510, Coyoacan, Circuito Exterior, Mexico DF Mexico
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Koenig SG, Vandenbossche CP, Zhao H, Mousaw P, Singh SP, Bakale RP. A Facile Deprotection of Secondary Acetamides. Org Lett 2008; 11:433-6. [DOI: 10.1021/ol802482d] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Stefan G. Koenig
- Chemical Process Research and Development, Sepracor Inc., 84 Waterford Drive, Marlborough, Massachusetts 01752
| | - Charles P. Vandenbossche
- Chemical Process Research and Development, Sepracor Inc., 84 Waterford Drive, Marlborough, Massachusetts 01752
| | - Hang Zhao
- Chemical Process Research and Development, Sepracor Inc., 84 Waterford Drive, Marlborough, Massachusetts 01752
| | - Patrick Mousaw
- Chemical Process Research and Development, Sepracor Inc., 84 Waterford Drive, Marlborough, Massachusetts 01752
| | - Surendra P. Singh
- Chemical Process Research and Development, Sepracor Inc., 84 Waterford Drive, Marlborough, Massachusetts 01752
| | - Roger P. Bakale
- Chemical Process Research and Development, Sepracor Inc., 84 Waterford Drive, Marlborough, Massachusetts 01752
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Simón L, Goodman JM. The Mechanism of TBD-Catalyzed Ring-Opening Polymerization of Cyclic Esters. J Org Chem 2007; 72:9656-62. [DOI: 10.1021/jo702088c] [Citation(s) in RCA: 162] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Luis Simón
- Unilever Centre for Molecular Science Informatics, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
| | - Jonathan M. Goodman
- Unilever Centre for Molecular Science Informatics, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom
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van Dijk AJM, Heyligen T, Duchateau R, Meuldijk J, Koning CE. Polyamide Synthesis from 6-Aminocapronitrile, Part 1:N-Alkyl Amide Formation by Amine Amidation of a Hydrolyzed Nitrile. Chemistry 2007; 13:7664-72. [PMID: 17594705 DOI: 10.1002/chem.200601897] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The synthesis of N-hexylpentanamide from a stoichiometric amount of pentanenitrile and hexylamine has been studied as a model reaction for the synthesis of nylon-6 from 6-aminocapronitrile. The reaction was carried out under mild hydrothermal conditions and in the presence of a homogeneous ruthenium catalyst. For the mild hydrothermal conditions the presence of hexylamine distinctively increases the nitrile hydrolysis compared to the nitrile hydrolysis in the absence of hexylamine. Amine-catalyzed nitrile hydrolysis mainly produces the N-substituted amide. A clear product development is observed, consisting of first the terminal amide formation and second the accumulation of N-hexylpentanamide. With a maximum conversion of only 80 % after 18 h, the nitrile hydrolysis rate at 230 degrees C is still much too low for nylon-6 synthesis. Ruthenium dihydride phosphine was therefore used as a homogeneous catalyst, which significantly increases the nitrile hydrolysis rate. At a temperature of 140 degrees C and with only 0.5 mol % [RuH(2)(PPh(3))(4)] a 60 % nitrile conversion is already reached within 2 h. Initially the terminal amide is the sole product, which is gradually converted into N-hexylpentanamide. The reaction has a high initial rate, however, for higher conversions a strong decrease in hydrolysis rate is observed. This is ascribed to product inhibition, which results from the equilibrium nature of the reaction.
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Affiliation(s)
- Adrianus J M van Dijk
- Laboratory of Polymer Chemistry, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
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Kleinpeter E, Schulenburg A. Quantification of the Push−Pull Effect in Tolanes and a Revaluation of the Factors Affecting the 13C Chemical Shifts of the Carbon Atoms of the C⋮C Triple Bond. J Org Chem 2006; 71:3869-75. [PMID: 16674062 DOI: 10.1021/jo060199j] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Variously substituted tolanes were employed to show that the push-pull effect is also active in CC triple bonds by the successful correlation of the occupation quotient pi/pi of the pi orbital in resonance with the substituted phenyl moieties of tolanes versus the bond length of the CC triple bond. In addition, the influences of the ortho phenyl ring substituents on the 13C chemical shifts of the triple bond carbon atoms, which were estimated by Rubin et al.(4) to be "inapplicable for describing triple bond polarization", were re-evaluated, leading to the conclusion that, while anisotropic effects of ortho substituents are negligible, the steric ortho-substituent effects do in fact dominate the deviations obtained. A detailed theoretical NBO/NCS study has been employed to illuminate the facts of this case.
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Affiliation(s)
- Erich Kleinpeter
- Department of Chemistry, University of Potsdam, Post Office Box 60 15 53, D-14415 Potsdam, Germany.
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Contreras RH, Esteban AL, Díez E, Della EW, Lochert IJ, Dos Santos FP, Tormena CF. Experimental and Theoretical Study of Hyperconjugative Interaction Effects on NMR 1JCH Scalar Couplings. J Phys Chem A 2006; 110:4266-75. [PMID: 16553380 DOI: 10.1021/jp0555201] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hyperconjugative and electrostatic interactions effects on 1J(CH) spin-spin coupling constants (SSCCs) are critically studied from both theoretical and experimental points of view. A qualitative model is used to predict how the former affect such SSCCs, while electrostatic interactions are modeled with a point charge placed in the vicinity of the corresponding sigma(CH) bond. Hyperconjugative interactions are calculated using the "natural bond orbital" approach, and using the point-charge model, it is shown how intertwined are both types of interactions. Several members of the series 1-X-bicyclo[1.1.1]pentane and 1-X-3-methylbicyclo[1.1.1]pentane are chosen as model compounds for measuring 1J(CH) SSCCs; in some of them were performed also DFT-SSCC calculations. The strained cage substrate in these series defines strong sigma-hyperconjugative interactions, making these compounds excellent examples to verify the qualitative model presented in this work. It is verified that (a) hyperconjugative interactions from the sigma(CH) bond or into the sigma(CH) antibond containing the coupling nuclei yield a decrease of the corresponding 1J(CH) SSCC and (b) hyperconjugative interactions from other bonds involving the coupling C nucleus yield an increase of that 1J(CH) SSCC.
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Affiliation(s)
- Rubén H Contreras
- Departamento de Física, FCEyN, Universidad de Buenos Aires, Ciudad Universitaria, P. 1 and CONICET (C1428EHA) Buenos Aires, Argentina
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Belen’kii L, Gramenitskaya V, Evdokimenkova Y. The Literature of Heterocyclic Chemistry, Part IX, 2002–2004. ADVANCES IN HETEROCYCLIC CHEMISTRY 2006. [DOI: 10.1016/s0065-2725(06)92004-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Niemevz F, Link NP, Perillo IA, Orelli LR. Synthesis, NMR characterization and ab initio6-31G* study of 1-aryl-2,3-dialkyl-1,4,5,6-tetrahydropyrimidinium salts. J Heterocycl Chem 2005. [DOI: 10.1002/jhet.5570420410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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del Fernández-Alonso MC, Cañada J, Jiménez-Barbero J, Cuevas G. Theoretical Study of Inversion and Topomerization Processes of Substituted Cyclohexanes: The Relevance of the Energy 3D Hypersurface. Chemphyschem 2005; 6:671-80. [PMID: 15881583 DOI: 10.1002/cphc.200400495] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Although the potential energy surface of highly symmetric cyclohexane has been extensively reviewed, no attention has been paid to the study of the effect of substitution of a methylene group by a heteroatom. The substitution may cause changes in molecular symmetry as well as the dipole moment, and the unshared electron pairs associated with the heteroatom may also introduce changes in molecular reactivity. However, these phenomena are not yet completely understood. To address these issues, a rigorous description of the inversion-topomerization process of methylcyclohexane and a revision of the conformational potential energy of oxane and thiane are presented. Moreover, the usefulness of providing a three-dimensional representation of these processes is discussed. In the case of methylcyclohexane, calculations show that three transition states are associated with inversion and four more with topomerization. In contrast, for oxane and thiane, only two transition states are involved with inversion and two with topomerization. Two fundamental conclusions can be drawn from this study. The first is that the inversion process occurs through elementary, stages that we have denoted "conformational elemental stages", which is an analogous term to that used for reaction mechanism description (minima-transition state-minima) where several elemental steps take place. The second conclusion is that two independent processes, inversion and topomerization, are connected by some common conformers. The inversion process controls the ring interchange, while topomerization allows exchange between skewed boats.
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Takano Y, Houk KN. Conformational Preferences in the Transition States and Tetrahedral Intermediates of Transacylations. Relationships to Enzyme-Bound Conformations of Phosphonate Inhibitors of Lipases and Esterases. J Phys Chem A 2004. [DOI: 10.1021/jp045889a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Yu Takano
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569
| | - K. N. Houk
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569
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Tuttle T, Cerkovnik J, Plesnicar B, Cremer D. Hemiortho Esters and Hydrotrioxides as the Primary Products in the Low-Temperature Ozonation of Cyclic Acetals: An Experimental and Theoretical Investigation. J Am Chem Soc 2004; 126:16093-104. [PMID: 15584745 DOI: 10.1021/ja0450511] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Low-temperature ozonation (-78 degrees C) of 1,3-dioxolanes 1a-1f and 1,3-dioxanes 1g and h in acetone-d6, methyl acetate, and tert-butyl methyl ether produced both the corresponding hemiortho esters (2a-h, ROH) and acetal hydrotrioxides (3a-h, ROOOH) in molar ratios ROH/ROOOH ranging from 0.5 to 23. Both types of intermediates were fully characterized by 1H, 13C, and 17O NMR spectroscopy. DFT calculations suggest that ozone abstracts a hydride ion from 1 to form an ion pair, R+ -OOOH, which subsequently collapses to either the corresponding hemiortho ester (ROH) or the acetal hydrotrioxide (ROOOH). Hemiortho esters decomposed quantitatively into the corresponding hydroxy esters. Experimentally obtained activation parameters for the decomposition of 2a (E(a) = 13.5 +/- 1.0 kcal/mol, log A = 8.3 +/- 1.0) are in accord with a highly oriented transition state involving, according to B3LYP calculations (deltaH(a)(298) = 13.2 kcal/mol), two molecules of water as a bifunctional catalyst. This mechanism is also supported by the magnitude of the solvent isotope effect for the decomposition of 2e, i.e., k(H2O)/k(D2O) = 4.6 +/- 1.2. Besides the hydroxy esters and oxygen (3O2/1O2), dihydrogen trioxide (HOOOH) was formed in the decomposition of most of the acetal hydrotrioxides (ROOOH) investigated. The activation parameters for the decomposition of the hydrotrioxides 3a-e in various solvents were E(a) = 20 +/- 2 kcal/mol, log A = 13.5 +/- 1.5. Several mechanistic possibilities for the decomposition of ROOOH were tested by experiment and theory. The formation of the hydroxy esters and oxygen could be explained by the intramolecular transfer of the proton to form the hydroxy ester. The assistance of water in the decomposition of ROOOH to form the hydroxy esters, either directly or via hemiortho esters, was also investigated. According to DFT calculations, the formation of a hydroxy ester via hemiortho ester is energetically more favorable (deltaH(a)(298) = 14.5 kcal/mol), again due to the catalytic effect of two water molecules. HOOOH generation requires the involvement of water in the decomposition of ROOOH where the direct formation out of ROOOH is energetically preferred. The energy for a reaction between two molecules of water and singlet oxygen (delta1O2) is too high to occur in solution.
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Affiliation(s)
- Tell Tuttle
- Department of Theoretical Chemistry, University of Göteborg, Reutersgatan 2, S-41320, Göteborg, Sweden
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Tormena CF, Rittner R, Contreras RH, Peralta JE. Anomeric Effect on Geminal and Vicinal JHH NMR Coupling Constants. J Phys Chem A 2004. [DOI: 10.1021/jp047226z] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Cláudio F. Tormena
- Departamento de Química, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil, Physical-Organic Chemistry Laboratory, Instituto de Química, Universidade Estadual de Campinas, Caixa Postal 6154 CEP:13084-971, Campinas, São Paulo, Brazil, and Department of Physics, University of Buenos Aires, Ciudad Universitaria, Pab. 1, (1428) Buenos Aires, Argentina
| | - Roberto Rittner
- Departamento de Química, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil, Physical-Organic Chemistry Laboratory, Instituto de Química, Universidade Estadual de Campinas, Caixa Postal 6154 CEP:13084-971, Campinas, São Paulo, Brazil, and Department of Physics, University of Buenos Aires, Ciudad Universitaria, Pab. 1, (1428) Buenos Aires, Argentina
| | - Rubén H. Contreras
- Departamento de Química, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil, Physical-Organic Chemistry Laboratory, Instituto de Química, Universidade Estadual de Campinas, Caixa Postal 6154 CEP:13084-971, Campinas, São Paulo, Brazil, and Department of Physics, University of Buenos Aires, Ciudad Universitaria, Pab. 1, (1428) Buenos Aires, Argentina
| | - Juan E. Peralta
- Departamento de Química, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14040-901 Ribeirão Preto, SP, Brazil, Physical-Organic Chemistry Laboratory, Instituto de Química, Universidade Estadual de Campinas, Caixa Postal 6154 CEP:13084-971, Campinas, São Paulo, Brazil, and Department of Physics, University of Buenos Aires, Ciudad Universitaria, Pab. 1, (1428) Buenos Aires, Argentina
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Sharavanan K, Komber H, Fischer D, Böhme F. Hydrolytic degradation of polyamidines and its potential application in controlled release of active agents. POLYMER 2004. [DOI: 10.1016/j.polymer.2004.01.055] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Mizyed S, Wright JEI, Byczynski B, Berti PJ. Identification of the catalytic residues of AroA (Enolpyruvylshikimate 3-phosphate synthase) using partitioning analysis. Biochemistry 2003; 42:6986-95. [PMID: 12795593 DOI: 10.1021/bi027217l] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AroA (EPSP synthase) catalyzes carboxyvinyl transfer through addition of shikimate 3-phosphate (S3P) to phosphoenolpyruvate (PEP) to form a tetrahedral intermediate (THI), followed by phosphate elimination to give enolpyruvylshikimate 3-phosphate (EPSP). A novel approach, partitioning analysis, was used to elucidate the roles of catalytic residues in each step of the reaction. Partitioning analysis involved trapping and purifying [1-(14)C]THI, degrading it with AroA, and quantitating the products. Wild-type AroA gave a partitioning factor, f(PEP) = 0.25 +/- 0.02 at pH 7.5, where f(PEP) = [[1-(14)C]PEP]/([[1-(14)C]PEP] + [[1-(14)C]EPSP]). Eighteen mutations were made to 14 amino acids to discover which residues preferentially catalyzed either the addition or the elimination step. Mutating a residue catalyzing one step (e.g., addition) should change f(PEP) to favor the opposite step (e.g., elimination). No mutants caused large changes in f(PEP), with experimental values from 0.07 to 0.41. This implied that there are no side chains that catalyze only addition or elimination, which further implied that the same residues are general acid/base catalysts in both forward and reverse THI breakdown. Only Lys22 (protonating S3P hydroxyl or phosphate) and Glu341 (deprotonating C3 of PEP) are correctly situated in the active site. In the overall reaction, Lys22 would act as a general base during addition, while Glu341 would act as a general acid. Almost half of the mutations (eight of 18) caused a >1000-fold decrease in specific activity, demonstrating that a large number of residues are important for transition state stabilization, "ensemble catalysis", in contrast to some enzymes where a single amino acid can be responsible for up to 10(8)-fold catalytic enhancement.
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Affiliation(s)
- Shehadeh Mizyed
- Department of Chemistry, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4M1, Canada
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Cuevas G, Juaristi E. Manifestation of stereoelectronic effects on the calculated carbon-hydrogen bond lengths and one bond (1)J(C-H) NMR coupling constants in cyclohexane, six-membered heterocycles, and cyclohexanone derivatives. J Am Chem Soc 2002; 124:13088-96. [PMID: 12405836 DOI: 10.1021/ja020317u] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cyclohexane (1), oxygen-, sulfur-, and/or nitrogen-containing six-membered heterocycles 2-5, cyclohexanone (6), and cyclohexanone derivatives 7-16 were studied theoretically [B3LYP/6-31G(d,p) and PP/IGLO-III//B3LYP/6-31G(d,p) methods] to determine the structural (in particular C-H bond distances) and spectroscopic (specifically, one bond (1)J(C-H) NMR coupling constants) consequences of stereoelectronic hyperconjugative effects. The results confirm the importance of n(X) --> sigma*(C-H)(app) (where X = O, N), sigma(C-H)(ax) --> pi*(C=O), sigma(S-C) --> sigma*(C-H)(app), sigma(C-S)-->sigma*(C-H)(app), beta-n(O) --> sigma*(C-H), and sigma(C-H) --> sigma*(C-H)(app) hyperconjugation, as advanced in previous theoretical models. Calculated r(C-H) bond lengths and (1)J(C-H) coupling constants for C-H bonds participating in more than one hyperconjugative interaction show additivity of the effects.
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Affiliation(s)
- Gabriel Cuevas
- Instituto de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, Apdo. Postal 70213, 04510 México, D.F., México.
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