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Saha J, Banerjee S, Malo S, Das AK, Das I. A Torquoselective Thermal 6π-Electrocyclization Approach to 1,4-Cyclohexadienes via Solvent-Aided Proton Transfer: Experimental and Theoretical Studies. Chemistry 2024; 30:e202304009. [PMID: 38179806 DOI: 10.1002/chem.202304009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 12/26/2023] [Accepted: 01/05/2024] [Indexed: 01/06/2024]
Abstract
The thermal 6π-electrocyclization of hexatriene typically delivers 1,3-cyclohexadiene (1,3-CHD). However, there is only limited success in directly synthesizing 1,4-cyclohexadiene (1,4-CHD) using such an approach, probably due to the difficulty in realizing thermally-forbidden 1,3-hydride shift after electrocyclic ring closure. The present study shows that by heating (2E,4E,6E)-hexatrienes bearing ester or ketone substituents at the C1-position in a mixture of toluene/MeOH or EtOH (2 : 1) solvents at 90-100 °C, 1,4-CHDs can be selectively synthesized. This is achieved through a torquoselective disrotatory 6π-electrocyclic ring closure followed by a proton-transfer process. The success of this method depends on the polar protic solvent-assisted intramolecular proton transfer from 1,3-CHD to 1,4-CHD, which has been confirmed by deuterium-labeling experiments. There are no reports to date for such a solvent-assisted isomerization. Density functional theory (DFT) studies have suggested that forming 1,3-CHD and subsequent isomerization is a thermodynamically feasible process, regardless of the functional groups involved. Two possible successive polar solvent-assisted proton-transfer pathways have been identified for isomerization.
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Affiliation(s)
- Jayanta Saha
- Organic and Medicinal Chemistry Division, CSIR-Indian Institute of Chemical BiologyJadavpur, Kolkata, 700032, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Soumadip Banerjee
- School of Mathematical and Computational Sciences, Indian Association for the Cultivation of Science Jadavpur, Kolkata, 700032, India
| | - Sidhartha Malo
- Organic and Medicinal Chemistry Division, CSIR-Indian Institute of Chemical BiologyJadavpur, Kolkata, 700032, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Abhijit Kumar Das
- School of Mathematical and Computational Sciences, Indian Association for the Cultivation of Science Jadavpur, Kolkata, 700032, India
| | - Indrajit Das
- Organic and Medicinal Chemistry Division, CSIR-Indian Institute of Chemical BiologyJadavpur, Kolkata, 700032, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India
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Arfan NHBZ, Hamid MHSA, Sheikh NS. A computational investigation towards substitution effects on 8π electrocyclisation of conjugated 1,3,5,7-octatetraenes. RSC Adv 2023; 13:30787-30797. [PMID: 37869396 PMCID: PMC10587816 DOI: 10.1039/d3ra05127g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Accepted: 10/09/2023] [Indexed: 10/24/2023] Open
Abstract
A computational investigation using M06-2X/6-31+G(d) method is reported for the substitution effects on 8π electrocyclisation of conjugated octatetraene. This systematic study describes the mono- and di-substitution effect across the 1,3,5,7-octatetraene skeleton. A general preference of the outward substitution over the inward, at C1 position of the monosubstituted system is observed. However, mesomerically electron donating group (-NH2 and -OH) display an opposite effect with respect to secondary orbital interaction (SOI) between the lone pair on the substituent and the orbital. A comparative evaluation on the computed activation energies for the 1-, 2-, 3-, and 4-monosubstituted system showed an insignificant impact on the rate of the reaction, in contrast to the electrocyclic ring closure of the unsubstituted compound. Computations of disubstituted system are more pronounced, where a remarkable acceleration is observed for 2-NO2-7-NO2 substituted octatetraene at 4.9 kcal mol-1, and a noticeable deceleration for 4-CH3-5-CH3 substituted octatetraene at 25.4 kcal mol-1 from the parent molecule, 17.0 kcal mol-1. A visible accelerated effects are commonly exhibited by the substitution on the terminal double bonds (C1, C2, C7, and C8), that are 1,2-, 1,7-, 1,8-, and 2,7-patterns, in regard to the greater orbital interaction for the new σ-bond formation. Despite the unfavourable steric clashes of the substituents in the 1,8-system, an apparent reduction in the energy barrier up to 7.4 kcal mol-1 is computed for 1-NH2-8-NO2 system from 17.0 kcal mol-1. This is due to the synergistic effect of the electron donor and electron acceptor, enhancing the stability of the transition structure. The electrocyclic ring closure involving vicinal substitution patterns, such as 1,2-, 2,3-, 3,4-, and 4,5-systems are critically dominated by steric crowding between the adjacent functional groups. In certain cases of the 1,2-substituted system, a noticeable accelerated effects are found for 1-NH2-2-NH2-substituted compound (9.7 kcal mol-1) due to an increased in electronic density on the substituted terminal double bond (C1-C2), hence favouring the formation of the new σ-bond.
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Affiliation(s)
- Nur Hazimah B Z Arfan
- Chemical Sciences, Faculty of Science, Universiti Brunei Darussalam Jalan Tungku Link, Gadong BE1413 Brunei Darussalam
| | - Malai Haniti S A Hamid
- Chemical Sciences, Faculty of Science, Universiti Brunei Darussalam Jalan Tungku Link, Gadong BE1413 Brunei Darussalam
| | - Nadeem S Sheikh
- Chemical Sciences, Faculty of Science, Universiti Brunei Darussalam Jalan Tungku Link, Gadong BE1413 Brunei Darussalam
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Jänner S, Isak D, Li Y, Houk KN, Miller AK. Bioinspired Asymmetric Total Synthesis of Emeriones A–C**. Angew Chem Int Ed Engl 2022; 61:e202205878. [PMID: 35670768 PMCID: PMC9401028 DOI: 10.1002/anie.202205878] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Indexed: 01/10/2023]
Abstract
We report asymmetric bioinspired total syntheses of the fungal metabolites emeriones A–C via stereoselective oxidations of two bicyclo[4.2.0]octadiene diastereomers. The central bicyclic scaffolds are prepared in an 8π/6π electrocyclization cascade of a stereodefined pentaene, which contains the fully assembled side chains of the emeriones. The anti‐aldol side chain is made using a Paterson‐aldol addition, and the epoxide of the dioxabicyclo[3.1.0]hexane side chain via ring‐closure onto an oxidized acetal. Our work has enabled the structural revision of emerione C, and resulted in the synthesis of a “missing” family member, which we call emerione D. DFT calculations identified two methyl groups that govern torquoselectivity in the 8π/6π cascade.
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Affiliation(s)
- Sven Jänner
- Cancer Drug Development Group German Cancer Research Center (DKFZ) Heidelberg Germany
| | - Daniel Isak
- Cancer Drug Development Group German Cancer Research Center (DKFZ) Heidelberg Germany
| | - Yuli Li
- Department of Chemistry School of Science Tianjin University Tianjin China
| | - Kendall N. Houk
- Department of Chemistry and Biochemistry University of California Los Angeles, CA USA
| | - Aubry K. Miller
- Cancer Drug Development Group German Cancer Research Center (DKFZ) Heidelberg Germany
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Jänner S, Isak D, Li Y, Houk KN, Miller AK. Bioinspired Asymmetric Total Synthesis of Emeriones A–C. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202205878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Sven Jänner
- German Cancer Research Centre: Deutsches Krebsforschungszentrum Cancer Drug Development GERMANY
| | - Daniel Isak
- German Cancer Research Centre: Deutsches Krebsforschungszentrum Cancer Drug Development GERMANY
| | - Yuli Li
- Tianjin University Department of Chemistry CHINA
| | - K. N. Houk
- UCLA: University of California Los Angeles Department of Chemistry and Biochemistry UNITED STATES
| | - Aubry Kern Miller
- German Cancer Research Center: Deutsches Krebsforschungszentrum Cancer Drug Development Im Neuenheimer Feld 280 69120 Heidelberg GERMANY
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Patel HD, Fallon T. Two Steps to Bicyclo[4.2.0]octadienes from Cyclooctatetraene: Total Synthesis of Kingianic Acid A. Org Lett 2022; 24:2276-2281. [PMID: 35293754 DOI: 10.1021/acs.orglett.2c00325] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Synthetic approaches to bicyclo[4.2.0]octadiene natural products frequently employ the synthesis of linear tetraenes to initiate a biosynthetic 8π/6π-electrocyclization cascade. This work forges a functionalized bicyclo[4.2.0]octadiene in two steps from cyclooctatetraene. The versatility of this method is demonstrated through natural product synthesis, including the first total synthesis of kingianic acid A and formal syntheses of kingianins A, D, and F and cryptobeilic acid D ethyl ester. The unexpected formation of an E,E,Z,E-tetraene byproduct is rationalized through density functional theory modeling.
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Affiliation(s)
- Harshal D Patel
- Department of Chemistry, The University of Adelaide, Adelaide, SA 5005 (Australia)
| | - Thomas Fallon
- Department of Chemistry, The University of Adelaide, Adelaide, SA 5005 (Australia)
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Yahiaoui O, Almass A, Fallon T. Total synthesis of endiandric acid J and beilcyclone A from cyclooctatetraene. Chem Sci 2020; 11:9421-9425. [PMID: 34094208 PMCID: PMC8161681 DOI: 10.1039/d0sc03073b] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 07/16/2020] [Indexed: 12/25/2022] Open
Abstract
The endiandric acids are classic targets in natural product synthesis. The spectacular 8π/6π-electrocylisation/intramolecular Diels-Alder (8π/6π/IMDA) reaction cascade at the heart of their biosynthesis has inspired practitioners and students of pericyclic chemistry for nearly forty years. All previous synthetic approaches have sought to prepare a linear tetraene and thereby initiate the cascade. In this communication we demonstrate the use of cyclooctatetraene to rapidly intercept the 8π/6π/IMDA cascade at the cyclooctatriene stage. Endiandric acid J and beilcyclone A are prepared for the first time in six and five steps, respectively. The strategy features a tactical overall anti-vicinal difunctionalisation of cyclooctatetraene through SN2' alkylation of cyclooctatetraene oxide followed by an intriguing tandem Claisen rearrangement/6π-electrocyclisation from the corresponding vinyl ether. This rapidly constructs an advanced bicyclo[4.2.0]octadiene aldehyde intermediate. Olefinations and intramolecular Diels-Alder cycloadditions complete the syntheses. This establishes a short and efficient new path to the endiandric acid natural products. DFT modelling predicts thermal racemisation of bicyclo[4.2.0]octadiene intermediates, dashing hopes of enantioselective synthesis.
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Affiliation(s)
- Oussama Yahiaoui
- Department of Chemistry, The University of Adelaide Adelaide SA 5005 Australia
| | - Adrian Almass
- Department of Chemistry, The University of Adelaide Adelaide SA 5005 Australia
| | - Thomas Fallon
- Department of Chemistry, The University of Adelaide Adelaide SA 5005 Australia
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Hu YJ, Li LX, Han JC, Min L, Li CC. Recent Advances in the Total Synthesis of Natural Products Containing Eight-Membered Carbocycles (2009-2019). Chem Rev 2020; 120:5910-5953. [PMID: 32343125 DOI: 10.1021/acs.chemrev.0c00045] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Natural products containing eight-membered carbocycles constitute a class of structurally intriguing and biologically important molecules such as the famous diterpenes taxol and vinigrol. Such natural products are being increasingly investigated because of their fascinating architectural features and potent medicinal properties. However, synthesis of natural products with cyclooctane moieties has proved to be highly challenging. This review highlights the recently completed total syntheses of natural products with eight-membered carbocycles with a focus on strategic considerations. A collection of 27 representative studies from the literature covering the decade from 2009 to 2019 is described in chronological order with relevant studies grouped together, including syntheses of the same natural product by different research groups using different strategies. Finally, a summary and outlook including a discussion of the major features of each strategy used in the syntheses are presented. This review illustrates the diversity and creativity in the elegant synthetic designs of eight-membered carbocycles. We hope this review will provide timely illumination and beneficial guidance for future synthetic efforts for organic chemists who are interested in this area.
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Affiliation(s)
- Ya-Jian Hu
- Shenzhen Grubbs Institute and Department of Chemistry, Southern University of Science and Technology (SUSTech), Shenzhen 518055, China
| | - Li-Xuan Li
- Shenzhen Grubbs Institute and Department of Chemistry, Southern University of Science and Technology (SUSTech), Shenzhen 518055, China
| | - Jing-Chun Han
- Shenzhen Grubbs Institute and Department of Chemistry, Southern University of Science and Technology (SUSTech), Shenzhen 518055, China
| | - Long Min
- Shenzhen Grubbs Institute and Department of Chemistry, Southern University of Science and Technology (SUSTech), Shenzhen 518055, China
| | - Chuang-Chuang Li
- Shenzhen Grubbs Institute and Department of Chemistry, Southern University of Science and Technology (SUSTech), Shenzhen 518055, China
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Quintela-Varela H, Jamieson CS, Shao Q, Houk KN, Trauner D. Bioinspired Synthesis of (-)-PF-1018. Angew Chem Int Ed Engl 2020; 59:5263-5267. [PMID: 31788926 PMCID: PMC9899496 DOI: 10.1002/anie.201912452] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Revised: 11/09/2019] [Indexed: 11/10/2022]
Abstract
The combination of electrocyclizations and cycloadditions accounts for the formation of a range of fascinating natural products. Cascades consisting of 8π electrocyclizations followed by a 6π electrocyclization and a cycloaddition are relatively common. We now report the synthesis of the tetramic acid PF-1018 through an 8π electrocyclization, the product of which is immediately intercepted by a Diels-Alder cycloaddition. The success of this pericyclic cascade was critically dependent on the substitution pattern of the starting polyene and could be rationalized through DFT calculations. The completion of the synthesis required the instalment of a trisubstituted double bond by radical deoxygenation. An unexpected side product formed through 4-exo-trig radical cyclization could be recycled through an unprecedented triflation/fragmentation.
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Affiliation(s)
- Hugo Quintela-Varela
- Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 Müchen (Germany),Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003 (USA)
| | - Cooper S. Jamieson
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095 (USA)
| | - Qianzhen Shao
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095 (USA),The College of Chemistry, Nankai University, Tianjin 300071 (China)
| | - K. N. Houk
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095 (USA)
| | - Dirk Trauner
- Department of Chemistry, New York University, 100 Washington Square East, New York, NY 10003 (USA)
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Quintela‐Varela H, Jamieson CS, Shao Q, Houk KN, Trauner D. Bioinspired Synthesis of (−)‐PF‐1018. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201912452] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Hugo Quintela‐Varela
- Department of Chemistry Ludwig-Maximilians-Universität München Butenandtstrasse 5–13 81377 München Germany
- Department of Chemistry New York University 100 Washington Square East New York NY 10003 USA
| | - Cooper S. Jamieson
- Department of Chemistry and Biochemistry University of California, Los Angeles Los Angeles CA 90095 USA
| | - Qianzhen Shao
- Department of Chemistry and Biochemistry University of California, Los Angeles Los Angeles CA 90095 USA
- The College of Chemistry Nankai University Tianjin 300071 China
| | - K. N. Houk
- Department of Chemistry and Biochemistry University of California, Los Angeles Los Angeles CA 90095 USA
| | - Dirk Trauner
- Department of Chemistry New York University 100 Washington Square East New York NY 10003 USA
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Kron KJ, Kosich M, Cave RJ, Vosburg DA. Divergent Diels-Alder Reactions in the Biosynthesis and Synthesis of Endiandric-Type Tetracycles: A Computational Study. J Org Chem 2018; 83:10941-10947. [PMID: 30113843 DOI: 10.1021/acs.joc.8b01594] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Endiandric acids and related polyketide natural products arise from polyene precursors and occur naturally as fused and bridged tetracycles. In some cases, the intramolecular Diels-Alder reactions that produce fused and bridged tetracycles result from a diene tether that may act as either a 4π or 2π component in the cycloaddition. To examine the preference for fused or bridged products, we applied density functional theory (using the M06-2X and B3LYP functionals) to reactants with various substituents for both fused and bridged transition states. Fused products were generally preferred except when disfavored by extreme steric hindrance (e.g., a tert-butyl group). These computational results are consistent with experimental data and suggest the existence of as-yet undiscovered natural products.
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Affiliation(s)
- Kareesa J Kron
- Department of Chemistry , Harvey Mudd College , 301 Platt Boulevard , Claremont , California 91711-5901 , United States
| | - Mikaela Kosich
- Department of Chemistry , Harvey Mudd College , 301 Platt Boulevard , Claremont , California 91711-5901 , United States
| | - Robert J Cave
- Department of Chemistry , Harvey Mudd College , 301 Platt Boulevard , Claremont , California 91711-5901 , United States
| | - David A Vosburg
- Department of Chemistry , Harvey Mudd College , 301 Platt Boulevard , Claremont , California 91711-5901 , United States
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Palazzo TA, Mose R, Jørgensen KA. Cycloadditionen: Warum ist der Übergang von sechs zu zehn Elektronen so schwer? Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201701085] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
| | - Rasmus Mose
- Department of Chemistry; Aarhus University; DK-8000 Aarhus C Dänemark
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Cycloaddition Reactions: Why Is It So Challenging To Move from Six to Ten Electrons? Angew Chem Int Ed Engl 2017; 56:10033-10038. [DOI: 10.1002/anie.201701085] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 04/06/2017] [Indexed: 12/26/2022]
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Boon BA, Green AG, Liu P, Houk KN, Merlic CA. Using Ring Strain to Control 4π-Electrocyclization Reactions: Torquoselectivity in Ring Closing of Medium-Ring Dienes and Ring Opening of Bicyclic Cyclobutenes. J Org Chem 2017; 82:4613-4624. [DOI: 10.1021/acs.joc.7b00203] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Byron A. Boon
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Aaron G. Green
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Peng Liu
- Department
of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260-3900, United States
| | - K. N. Houk
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Craig A. Merlic
- Department
of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
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Lindel T. Chemistry and Biology of the Pyrrole–Imidazole Alkaloids. THE ALKALOIDS: CHEMISTRY AND BIOLOGY 2017; 77:117-219. [DOI: 10.1016/bs.alkal.2016.12.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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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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