1
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Bai M, Feng Z, Li J, Tantillo DJ. Bouncing off walls - widths of exit channels from shallow minima can dominate selectivity control. Chem Sci 2020; 11:9937-9944. [PMID: 34094255 PMCID: PMC8162169 DOI: 10.1039/d0sc04036c] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A selectivity model based on the widths of pathways to competing products, rather than barrier heights, is formulated for the butadiene + allyl cation reaction. This model was arrived at via analysis of stationary points, intrinsic reaction coordinates, potential energy surface shapes and direct dynamics trajectories, all determined using quantum chemical methods.
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Affiliation(s)
- Mengna Bai
- School of Chemistry and Chemical Engineering, Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University No. 55 Daxuecheng South Rd., Shapingba Chongqing 401331 China.,Department of Chemistry, University of California Davis One Shields Avenue Davis CA 95616 USA
| | - Zhitao Feng
- Department of Chemistry, University of California Davis One Shields Avenue Davis CA 95616 USA
| | - Jun Li
- School of Chemistry and Chemical Engineering, Chongqing Key Laboratory of Theoretical and Computational Chemistry, Chongqing University No. 55 Daxuecheng South Rd., Shapingba Chongqing 401331 China
| | - Dean J Tantillo
- Department of Chemistry, University of California Davis One Shields Avenue Davis CA 95616 USA
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2
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Saima B, Wang YA, Hussain R, Muhammad S, Ayub K. Thermal decomposition of syn- and anti-dihydropyrenes; functional group-dependent decomposition pathway. J Mol Model 2019; 25:215. [PMID: 31292739 DOI: 10.1007/s00894-019-4052-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 04/24/2019] [Indexed: 10/26/2022]
Abstract
Syn and anti dihydropyrene (DHP) are excellent thermochromes, and therefore extensively studied for their thermochromic and photochromic properties, respectively. However, they suffer from thermal decomposition due to thermal instability. In this study, we thoroughly investigated pathways for the thermal decomposition of anti- and syn- dihydropyrenes through computational methods. The decomposition pathways include sigmatropic shift and hemolytic and heterolytic (cationic and anionic) cleavages. The decomposition pathway is influenced not only by the dihydropyrene (syn- or anti-) but also by the functional groups present. For anti-dihydropyrenes, sigmatropic shift is the most plausible pathways for CN and CHO internal groups. The cascade of sigmatropic shifts is followed by elimination to deliver substituted pyrenes. For CH3- and H- dihydropyrenes, hemolytic cleavage of the internal groups is the most plausible pathway for decomposition to pyrenes. The pathway is changed to heterolytic cleavage when the internal groups on the dihydropyrenes are Cl-, Br-, and SMe-. Comparison of the activation barriers for syn (30.18 kcal mol-1) and anti (32.10 kcal mol-1) dimethyldihydropyrenes for radical pathway reveal that decomposition of syn- DHP is more facile over anti-, which is consistent with the experimental observation. The decomposition pathway for syn-dihydropyrene is also hemolytic in cleavage when the internal groups are methyl and hydrogen. Syn-dihydropyrenes (symmetrical or unsymmetrical) bearing CN group do not follow sigmatropic shift, quite contrary to the anti-dihydropyrene. The lack of tendency of the syn-dihydropyrene for sigmatropic shift is rationalized on the planarity of the scaffold. The results of the theoretical study are consistent with the experimental observations. The results here help in understanding the behavior of substituents on the dihydropyrene scaffold, which will be useful in designing new molecules with improved thermal stabilities. Graphical abstract Functional group dependent decomposition pathways of dihydropyrenes.
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Affiliation(s)
- Bibi Saima
- Department of Chemistry, COMSATS University, Abbottabad Campus, Abbottabad, 22060, Pakistan
| | - Yan Alexander Wang
- Department of Chemistry, University of British Columbia, Vancouver, V6T 1Z1, Canada
| | - Riaz Hussain
- Department of Chemistry, University of Okara, Okara, Punjab, Pakistan
| | - Shabbir Muhammad
- Department of Physics, College of Science, King Khalid University, Abha, Saudi Arabia.,Research Center for Advanced Materials Science (RCAMS), King Khalid University, Abha, Saudi Arabia
| | - Khurshid Ayub
- Department of Chemistry, COMSATS University, Abbottabad Campus, Abbottabad, 22060, Pakistan.
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3
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Saima B, Khan N, Al-Faiyz YSS, Ludwig R, Rehman W, Habib-Ur-Rehman M, Sheikh NS, Ayub K. Photo-tunable linear and nonlinear optical response of cyclophanediene-dihydropyrene photoswitches. J Mol Graph Model 2019; 88:261-272. [PMID: 30780115 DOI: 10.1016/j.jmgm.2019.01.019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2018] [Revised: 01/31/2019] [Accepted: 01/31/2019] [Indexed: 11/26/2022]
Abstract
Cyclophanediene (CPD)-dihydropyrene (DHP) is a negative T-type photochrome pair having a thermodynamically stable colored form, i.e., DHP. Interconversion between cyclophanediene and dihydropyrene is associated with significant changes in dipole moment, absorption wavelength and polarizability, which can impart substantial linear and nonlinear optical response. In this study, phototunable linear and nonlinear optical response of cyclophanediene-dihdyropyrene photoswitches is described. Cyclophanedienes and dihydropyrenes are functionalized at the internal position for maximum changes in volume and polarizability. The UV-Vis spectra are calculated at ɷB97XD, which was validated through a benchmark approach. An excellent correlation is observed between theoretical and experimental absorption spectra. Several CPD-DHP pairs have been recognized for clean interconversion in UV-Vis light without formation of a photostationary state. Nonlinear optical response of dihydropyrenes is remarkably higher than that of cyclophanedienes. In general, the calculated hyperpolarizability values of dihydropyrenes are about two to three orders of magnitude higher than those for cyclophanedienes. The trends in calculated hyperpolarizabilities are rationalized through two level method. The high nonlinear optical response of dihydropyrenes stems from low excitation energies. The remarkable difference in hyperpolarizabilities of these isomeric forms paves path for the design of phototunable nonlinear optical materials.
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Affiliation(s)
- Bibi Saima
- Department of Chemistry, COMSATS University, Abbottabad Campus, 22060, Pakistan
| | - Nasir Khan
- Department of Chemistry, Hazara University, Mansehra, Pakistan
| | - Yasair S S Al-Faiyz
- Department of Chemistry, College of Science, King Faisal University, P.O. Box 380, Al-Ahsa, 31982, Saudi Arabia
| | - Ralf Ludwig
- Department of Physical Chemistry, University of Rostock, Dr.-Lorenz-Weg 1, 18059, Rostock, Germany; Leibniz-Institut für Katalyse an der Universität Rostock e, V. Alebert-Einstein-Strasse 29a, 18059, Rostock, Germany
| | - Wajid Rehman
- Department of Chemistry, Hazara University, Mansehra, Pakistan
| | - Mian Habib-Ur-Rehman
- Department of Chemistry, University of Education Lahore, Faisalabad Campus, Pakistan
| | - Nadeem S Sheikh
- Department of Chemistry, College of Science, King Faisal University, P.O. Box 380, Al-Ahsa, 31982, Saudi Arabia.
| | - Khurshid Ayub
- Department of Chemistry, COMSATS University, Abbottabad Campus, 22060, Pakistan.
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4
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Parent JF, Deslongchamps P. High-Temperature Isomerization of Benzenoid Polycyclic Aromatic Hydrocarbons. Analysis through the Bent Bond and Antiperiplanar Hypothesis Orbital Model. J Org Chem 2018; 83:3299-3304. [PMID: 29470083 DOI: 10.1021/acs.joc.8b00095] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
L. T. Scott has discovered the 1,2-swapping of carbon and hydrogen atoms which is known to take place on benzenoid aromatics (up to ∼1000 °C range). For example, 13C-1-naphthalene is specifically converted to 13C-2-naphthalene, and there is evidence that this occurs through the formation of benzofulvene and a naphthalene-carbene intermediate. Application of the bent bond/antiperiplanar hypothesis leads to the postulate that higher in energy pyramidal singlet diradical intermediates can be used to propose a mechanism that rationalizes various atom rearrangements on benzenoid aromatics and related isomeric compounds.
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Affiliation(s)
- Jean-François Parent
- Département de Chimie, Faculté des Sciences et de Génie , 1045 avenue de la médecine , Université Laval , Québec , QC G1 V 0A6 , Canada
| | - Pierre Deslongchamps
- Département de Chimie, Faculté des Sciences et de Génie , 1045 avenue de la médecine , Université Laval , Québec , QC G1 V 0A6 , Canada
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5
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Rajale T, Sharma S, Unruh DK, Stroud DA, Birney DM. A pseudopericyclic [3,5]-sigmatropic rearrangement of a coumarin trichloroacetimidate derivative. Org Biomol Chem 2018; 16:874-879. [DOI: 10.1039/c7ob02335a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
A Woodward–Hoffmann forbidden, eight-centered transition state leads to the sole product of a pentadienyl imidate rearrangement.
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Affiliation(s)
- Trideep Rajale
- Department of Chemistry and Biochemistry
- Texas Tech University
- Lubbock
- USA
- Center for Integrated Nanotechnologies
| | - Shikha Sharma
- Department of Chemistry and Biochemistry
- Texas Tech University
- Lubbock
- USA
| | - Daniel K. Unruh
- Department of Chemistry and Biochemistry
- Texas Tech University
- Lubbock
- USA
| | - Daniel A. Stroud
- Department of Chemistry and Biochemistry
- Texas Tech University
- Lubbock
- USA
| | - David M. Birney
- Department of Chemistry and Biochemistry
- Texas Tech University
- Lubbock
- USA
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6
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Nguyen QNN, Tantillo DJ. When To Let Go—Diradical Intermediates from Zwitterionic Transition State Structures? J Org Chem 2016; 81:5295-302. [DOI: 10.1021/acs.joc.6b00533] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Q. Nhu N. Nguyen
- Department
of Chemistry, University of California—Davis, Davis, California 95616, United States
| | - Dean J. Tantillo
- Department
of Chemistry, University of California—Davis, Davis, California 95616, United States
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7
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Deslongchamps G, Deslongchamps P. Bent bonds and the antiperiplanar hypothesis – a simple model to rationalize [1,3]-sigmatropic alkyl shifts. Org Biomol Chem 2016; 14:7754-67. [DOI: 10.1039/c6ob01139j] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The stereochemical outcome of [1,3]-sigmatropic rearrangements can be rationalized by the use of olefinic tau (τ) bonds, and by considering that diradical intermediates have pyramidal character.
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8
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Towards thermally stable cyclophanediene-dihydropyrene photoswitches. J Mol Model 2015; 21:148. [PMID: 25986774 DOI: 10.1007/s00894-015-2695-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Accepted: 05/03/2015] [Indexed: 10/23/2022]
Abstract
Cyclophanediene dihydropyrenes (CPD-DHP) are photochromic compounds because they change their color by irradiation with lights of different color. Potential use of CPD-DHP photoswitch in memory devices requires a very slow thermal return in the dark in the absence of any side reaction. Herein, thermal return of CPDs to DHPs, and an unwanted sigmatropic shift in DHP is studied through density functional theory calculations at (U)B3LYP/6-31+G(d). The thermal return occurs through symmetry forbidden conrotatory electrocyclic reaction. Dimethyl amino CPD-DHP photoswitch pair has the highest activation barrier for electrocyclization and sigmatropic shifts. The lowest activation barrier for symmetry forbidden electrocyclization is observed for GeBr3 functionalized CPD. An unprecedented decomposition pathway involving elimination of the internal substituents is predicted for Cl, Br and SMe functionalized DHPs. This study shows great promise in understanding the Woodward Hoffmann forbidden processes and, in reducing the synthetic efforts toward robust photochromes for memory applications.
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9
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Goossens H, Winne JM, Wouters S, Hermosilla L, De Clercq PJ, Waroquier M, Van Speybroeck V, Catak S. Possibility of [1,5] sigmatropic shifts in bicyclo[4.2.0]octa-2,4-dienes. J Org Chem 2015; 80:2609-20. [PMID: 25615563 DOI: 10.1021/jo5027639] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The thermal equilibration of the methyl esters of endiandric acids D and E was subject to a computational study. An electrocyclic pathway via an electrocyclic ring opening followed by a ring flip and a subsequent electrocyclization proposed by Nicolaou [ Nicolaou , K. C. ; Chen , J. S. Chem. Soc. Rev. 2009 , 38 , 2993 ], was computationally explored. The free-energy barrier for this electrocyclic route was shown to be very close to the bicyclo[4.2.0]octa-2,4-diene reported by Huisgen [ Huisgen , R. ; Boche , G. ; Dahmen , A. ; Hechtl , W. Tetrahedron Lett. 1968 , 5215 ]. Furthermore, the possibility of a [1,5] sigmatropic alkyl group shift of bicyclo[4.2.0]octa-2,4-diene systems at high temperatures was explored in a combined computational and experimental study. Calculated reaction barriers for an open-shell singlet biradical-mediated stepwise [1,5] sigmatropic alkyl group shift were shown to be comparable with the reaction barriers for the bicyclo[4.1.0]hepta-2,4-diene (norcaradiene) walk rearrangement. However, the stepwise sigmatropic pathway is suggested to only be feasible for appropriately substituted compounds. Experiments conducted on a deuterated analogous diol derivative confirmed the calculated (large) differences in barriers between electrocyclic and sigmatropic pathways.
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Affiliation(s)
- Hannelore Goossens
- Center for Molecular Modeling, Ghent University , Technologiepark 903, 9052 Zwijnaarde, Belgium
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10
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Abstract
Covering: up to 2014. Prenylated indole alkaloids comprise a large and structurally diverse family of natural products that often display potent biological activities. In recent years a large family of prenyltransferases that install prenyl groups onto the indole core have been discovered. While the vast majority of these enzymes are evolutionarily related and share a common protein fold, they are remarkably versatile in their ability to catalyze reverse and normal prenylations at all positions on the indole ring. This highlight article will focus on recent studies of the mechanisms utilized by indole prenyltransferases. While all of the prenylation reactions may follow a direct electrophilic aromatic substitution mechanism, studies of structure and reactivity suggest that in some cases prenylation may first occur at the nucleophilic C-3 position, and subsequent rearrangements then generate the final product.
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Affiliation(s)
- Martin E Tanner
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, V6T 1Z1, British Columbia, Canada.
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11
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Abstract
The indole prenyltransferases are a family of metal-independent enzymes that catalyze the transfer of a prenyl group from dimethylallyl diphosphate (DMAPP) onto the indole ring of a tryptophan residue. These enzymes are remarkable in their ability to direct the prenyl group in either a “normal” or “reverse” fashion to positions with markedly different nucleophilicity. The enzyme 4-dimethylallyltryptophan synthase (4-DMATS) prenylates the non-nucleophilic C-4 position of the indole ring in free tryptophan. Evidence is presented in support of a mechanism that involves initial ion pair formation followed by a reverse prenylation at the nucleophilic C-3 position. A Cope rearrangement then generates the C-4 normal prenylated intermediate and deprotonation rearomatizes the indole ring. The enzyme tryprostatin B synthase (FtmPT1) catalyzes the normal C-2 prenylation of the indole ring in brevianamide F (cyclo-L-Trp-L-Pro). It shares high structural homology with 4-DMATS, and evidence is presented in favor of an initial C-3 prenylation (either normal or reverse) followed by carbocation rearrangements to give product. The concept of a common intermediate that partitions to different products via rearrangements can help to explain how these evolutionarily related enzymes can prenylate different positions on the indole ring.
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12
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Sharma S, Rajale T, Cordes DB, Hung-Low F, Birney DM. Experimental and Computational Studies on the [3,3]- and [3,5]-Sigmatropic Rearrangements of Acetoxycyclohexadienones: A Non-ionic Mechanism for Acyl Migration. J Am Chem Soc 2013; 135:14438-47. [DOI: 10.1021/ja4077364] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shikha Sharma
- Department of Chemistry and
Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States
| | - Trideep Rajale
- Department of Chemistry and
Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States
| | - David B. Cordes
- Department of Chemistry and
Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States
| | - Fernando Hung-Low
- Department of Chemistry and
Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States
| | - David M. Birney
- Department of Chemistry and
Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States
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13
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Mahmoodi N, Tanner ME. Potential rearrangements in the reaction catalyzed by the indole prenyltransferase FtmPT1. Chembiochem 2013; 14:2029-37. [PMID: 24014462 DOI: 10.1002/cbic.201300385] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Indexed: 12/13/2022]
Abstract
The indole prenyltransferase FtmPT1 catalyzes the C-2 normal prenylation of brevianamide F (cyclo-L-Trp-L-Pro) to give tryprostatin B. A previous structural analysis and studies with alternate substrates suggest that the reaction might not proceed through a direct C-2 attack, but could involve a C-3 prenylation followed by a rearrangement. In this work we investigated the reactivity of FtmPT1 with tryptophan, 5-hydroxybrevianamide, and 2-methylbrevianamide, and isolated products that had been reverse prenylated at C-3 and normal prenylated at N-1, C-3, or C-4. The formation of these products can be rationalized through mechanisms involving either an initial C-3 normal or C-3 reverse prenylation. In addition, we demonstrate that a C-3 reverse prenylated indole can undergo a nonenzymatic aza-Cope rearrangement at 37 °C to give an N-1 normal prenylated product. Together, these studies broaden the known product scope of this interesting catalyst and suggest that alternative mechanisms might be operating.
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Affiliation(s)
- Niusha Mahmoodi
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1 (Canada)
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14
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Shahzad N, Nisa RU, Ayub K. Substituents effect on thermal electrocyclic reaction of dihydroazulene–vinylheptafulvene photoswitch: a DFT study to improve the photoswitch. Struct Chem 2013. [DOI: 10.1007/s11224-013-0212-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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15
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Sugden IJ, Plant DF, Bell RG. Thermal rearrangement mechanisms in icosahedral carboranes and metallocarboranes. Chem Commun (Camb) 2013; 49:975-7. [PMID: 23254297 DOI: 10.1039/c2cc37520f] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Ab initio MD and potential energy surface sampling has been used to study the rearrangement processes in carboranes and their derivatives. A new mechanism is found, in addition to those previously proposed. The fact that theoretical activation energies are lower than those observed experimentally, and the differing activity of technetium and rhenium complexes, are rationalised by orbital symmetry constraints.
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Affiliation(s)
- Isaac J Sugden
- University College London, Chemistry Department, 20 Gordon Street, London, WC1H0AJ, UK
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16
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Ishikawa A, Tanimura Y, Nakao Y, Sato H, Sakaki S. Complicated Electronic Process of C–C σ-Bond Activation of Cyclopropene by Ruthenium and Iridium Complexes: Theoretical Study. Organometallics 2012. [DOI: 10.1021/om300811g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Atsushi Ishikawa
- Department
of Molecular Engineering,
Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Yudai Tanimura
- Department
of Molecular Engineering,
Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Yoshihide Nakao
- Fukui Institute for Fundamental
Chemistry, Kyoto University, Nishihiraki-cho
34-4, Takano, Sakyo-ku, Kyoto 606-8103, Japan
| | - Hirofumi Sato
- Department
of Molecular Engineering,
Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Shigeyoshi Sakaki
- Fukui Institute for Fundamental
Chemistry, Kyoto University, Nishihiraki-cho
34-4, Takano, Sakyo-ku, Kyoto 606-8103, Japan
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17
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Heinrich N, Willis AC, Cade IA, Ho J, Coote ML, Banwell MG. Reversible Cyclopropane Ring-Cleavage Reactions within Etheno-Bridged [4.3.1]Propelladiene Frameworks Leading to Aza- and Oxa-[5.6.5.6]fenestratetraenes. Chemistry 2012; 18:13585-8. [DOI: 10.1002/chem.201202903] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Indexed: 11/09/2022]
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18
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Gutierrez O, Harrison JG, Pemberton RP, Tantillo DJ. Re-examining the mechanisms of competing pericyclic reactions of 1,3,7-octatriene. Chemistry 2012; 18:11029-35. [PMID: 22836223 DOI: 10.1002/chem.201201193] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2012] [Indexed: 11/07/2022]
Abstract
DFT (both B3LYP and M06-2X), CASSCF, and CASPT2 calculations were used to investigate competing [3, 3] and [3, 5] sigmatropic shifts and intramolecular [4+2] cycloaddition of 1,3,7-octatriene. In accord with previous results on 1,5-hexadiene, CASSCF calculations found both stepwise and concerted pathways for the [3, 3] rearrangement. For the competing [3, 5] sigmatropic rearrangement, CASSCF and CASPT2 calculations revealed three stepwise pathways with similar barriers. UB3LYP and UM06-2X calculations predicted a different potential energy landscape: no stepwise [3, 3] pathway, only two competing [3, 5] sigmatropic shifts, and an intramolecular Diels-Alder cycloaddition/homolytic ring-opening pathway. Significant lowering of barriers for all rearrangements was predicted for some 1,3,7-octatrienes with substituents at the 4- and 7-positions.
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Affiliation(s)
- Osvaldo Gutierrez
- Department of Chemistry, University of California-Davis, Davis, CA 95616, USA
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19
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Gilmore K, Manoharan M, Wu JIC, Schleyer PVR, Alabugin IV. Aromatic Transition States in Nonpericyclic Reactions: Anionic 5-Endo Cyclizations Are Aborted Sigmatropic Shifts. J Am Chem Soc 2012; 134:10584-94. [DOI: 10.1021/ja303341b] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Kerry Gilmore
- Department of Chemistry and
Biochemistry, Florida State University,
Tallahassee, Florida 32306-4390, United States
| | - Mariappan Manoharan
- School of Science, Engineering
and Mathematics, Bethune-Cookman University, Daytona Beach, Florida 32114, United States
| | - Judy I-Chia Wu
- Center for Computational Chemistry,
Department of Chemistry, University of Georgia, Athens, Georgia 30602-2525, United States
| | - Paul v. R. Schleyer
- Center for Computational Chemistry,
Department of Chemistry, University of Georgia, Athens, Georgia 30602-2525, United States
| | - Igor V. Alabugin
- Department of Chemistry and
Biochemistry, Florida State University,
Tallahassee, Florida 32306-4390, United States
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20
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Harrison JG, Tantillo DJ. Fusing cubanes to 1,5-hexadiene. Phys Chem Chem Phys 2012; 14:14756-9. [DOI: 10.1039/c2cp41844d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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21
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Lan Y, Houk KN. Mechanism and stereoselectivity of the stepwise 1,3-dipolar cycloadditions between a thiocarbonyl ylide and electron-deficient dipolarophiles: a computational investigation. J Am Chem Soc 2010; 132:17921-7. [PMID: 21121653 DOI: 10.1021/ja108432b] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The 1,3-dipolar cycloadditions of a thiocarbonyl ylide to dimethyl 2,3-dicyanofumarate and 2,3-dicyanomaleate have been studied with DFT computations. The first C-C bond is formed via an anti attack to produce a very polar, zwitterionic diradical. The low stereoselectivity of the reaction was found to arise from rotations about single bonds in the intermediates that compete with cyclization. A distortion-interaction energy analysis was performed to compare the stepwise and concerted mechanisms, and to explain why the stepwise mechanism is favored in this unusual case.
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Affiliation(s)
- Yu Lan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
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22
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Yamabe S, Yamazaki S. A remarkable difference in the deprotonation steps of the Friedel-Crafts acylation and alkylation reactions. J PHYS ORG CHEM 2009. [DOI: 10.1002/poc.1564] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Williams RV, Edwards WD, Mitchell RH, Robinson SG. A DFT Study of the Thermal, Orbital Symmetry Forbidden, Cyclophanediene to Dihydropyrene Electrocyclic Reaction. Predictions to Improve the Dimethyldihydropyrene Photoswitches. J Am Chem Soc 2005; 127:16207-14. [PMID: 16287311 DOI: 10.1021/ja054553r] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The orbital symmetry forbidden thermal electrocyclic equilibria between a series of cyclophanedienes and dimethyldihydropyrenes (CPD<==>DDPs) were studied using density functional theory (DFT). These reactions are important not only because of their fundamental interest but also in how they restrict the potential utility of the DDP photoswitches by limiting the thermal lifetime of the CPDs. The transition states (TSs) for these reactions could not be modeled using restricted DFT (RB3LYP) but were located using unrestricted DFT (UB3LYP). Each TS possesses significant biradical character as indicated by their spin contaminated wave functions, S2 not = 0. Specific substitution by nitrile or trifluoromethyl group(s) is predicted to strongly affect the magnitude of the activation barriers for these reactions. In particular, replacing the internal methyl groups of the CPDs/DDPs with nitrile groups is predicted to have the maximum effect and to raise the activation barriers and lifetimes of the CPDs considerably.
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Khuong KS, Jones WH, Pryor WA, Houk KN. The mechanism of the self-initiated thermal polymerization of styrene. Theoretical solution of a classic problem. J Am Chem Soc 2005; 127:1265-77. [PMID: 15669866 DOI: 10.1021/ja0448667] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Mayo and Flory mechanisms for the self-initiation of styrene polymerization were explored with B3LYP and BPW91 density functional calculations. The Diels-Alder dimer (AH) is the key intermediate, and the lowest energy pathway for AH formation is a stepwise mechanism via a gauche/sickle (*M2*Gs) or gauche/U-shaped (*M2*Gu) diradical. Ring closure of the 1,4-diradical to diphenylcyclobutane (DCB) is predicted to have a lower barrier than ring closure to AH. Dynamic effects are likely to play an important role in determining the rate of AH versus DCB formation. Hydrogen transfer from AH to styrene to generate two monoradical species is predicted to be a reasonable process that initiates monoradical polymerization.
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Affiliation(s)
- Kelli S Khuong
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA
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Augé F, Sapi J, Laronze JY. Computational insight into the thermal reactivity of N-methyl-3-cyanomethyl-2-vinylindole. Competition between two pericyclic reactions. Tetrahedron 2004. [DOI: 10.1016/j.tet.2004.05.031] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Leach AG, Goldstein E, Houk KN. A cornucopia of cycloadducts: theoretical predictions of the mechanisms and products of the reactions of cyclopentadiene with cycloheptatriene. J Am Chem Soc 2003; 125:8330-9. [PMID: 12837105 DOI: 10.1021/ja029694x] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The potential cycloaddition reactions between cyclopentadiene and cycloheptatriene have been explored theoretically. B3LYP/6-31G was used to locate the transition states, intermediates, and products for concerted pathways and stepwise pathways passing through diradical intermediates. Interconversions of various cycloadducts through sigmatropic shifts were also explored. CASPT2/6-31G single point calculations were employed to obtain independent activation energy estimates. MM3 was also used to compute reaction energetics. Several bispericyclic cycloadditions in which two cycloadducts are linked by a sigmatropic shift have been identified. B3LYP predicts, in line with frontier molecular orbital predictions, that the [6+4] cycloaddition is the favored concerted pathway, but an alternative [4+2] pathway is very close in energy. By contrast, CASPT2 predicts that a [4+2] cycloaddition is the preferred pathway. B3LYP predicts that the lowest energy path to many of the cycloadducts will involve diradical intermediates, whereas CASPT2 predicts that each of the products of orbital symmetry allowed reactions will be reached most readily by closed shell processes-concerted cycloadditions and sigmatropic shift rearrangements of cycloadducts.
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Affiliation(s)
- Andrew G Leach
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
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Zhang G, Li S, Jiang Y. Effects of Substitution on the Singlet−Triplet Energy Splittings and Ground-State Multiplicities of m-Phenylene-Based Diradicals: A Density Functional Theory Study. J Phys Chem A 2003. [DOI: 10.1021/jp022596d] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ganbing Zhang
- Department of Chemistry, Institute of Theoretical and Computational Chemistry, Lab of Mesoscopic Materials Science, Nanjing University, Nanjing 210093, People's Republic of China
| | - Shuhua Li
- Department of Chemistry, Institute of Theoretical and Computational Chemistry, Lab of Mesoscopic Materials Science, Nanjing University, Nanjing 210093, People's Republic of China
| | - Yuansheng Jiang
- Department of Chemistry, Institute of Theoretical and Computational Chemistry, Lab of Mesoscopic Materials Science, Nanjing University, Nanjing 210093, People's Republic of China
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Leach AG, Houk KN. The ene reactions of nitroso compounds involve polarized diradical intermediates. J Am Chem Soc 2002; 124:14820-1. [PMID: 12475303 DOI: 10.1021/ja012757b] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ene reactions of nitroso compounds were studied with B3LYP/6-31G* geometry optimizations and energy calculations, along with single point energy evaluations using CASPT2/6-31G** and UCCSD(T)/6-311+G* methods. Reactions of HNO with propene and of MeNO and p-NO2C6H4NO with propene or substituted alkenes were also studied. The reaction mechanism is stepwise and involves a polarized diradical intermediate. The electronic structure of this intermediate is between that of a closed shell polar species and that of a pure diradical, and it is stabilized by polar solvents. A weak C-N bonding interaction combined with a CH-O hydrogen bond leads to heightened barriers to rotation about formally single bonds compared to conventional diradicals. Consequently, rotation is slower than hydrogen abstraction and cyclization to form an aziridine N-oxide. This aziridine N-oxide does not lead to ene products without subsequent ring opening but provides a mechanism for the RNO moiety to translate from one end of the alkene to the other. B3LYP calculations are also able to reproduce kinetic isotope effects and regioselectivity.
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Affiliation(s)
- Andrew G Leach
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095-1569, USA
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