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Das P, DeSpain M, Ethridge A, Weaver JD. Exploiting Visible Light Triggered Formation of trans-Cyclohexene for the Contra-thermodynamic Protection of Alcohols. Org Lett 2023; 25:7316-7321. [PMID: 37773592 DOI: 10.1021/acs.orglett.3c02666] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/01/2023]
Abstract
We report herein a method for the contra-thermodynamic protection and thermodynamic deprotection of alcohols in which all reagents are returned to their original state. This is accomplished by the use of visible light photochemical energy to drive the formation of a highly strained trans-(Z)-cyclohexene. At STP the product ethers contain more potential energy than the starting materials and, thus, can be catalytically returned to the starting materials, effectively realizing a protection-deprotection scheme paid for with an energy currency.
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Affiliation(s)
- Pritha Das
- 107 Physical Science, Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Megan DeSpain
- 107 Physical Science, Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Avery Ethridge
- 107 Physical Science, Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Jimmie D Weaver
- 107 Physical Science, Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States
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Schoch TD, Weaver JD. Efforts toward Synthetic Photosynthesis: Visible Light-Driven CO 2 Valorization. J Am Chem Soc 2023; 145:14945-14951. [PMID: 37390455 DOI: 10.1021/jacs.3c04837] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/02/2023]
Abstract
Current methods of urethane preparation from amines invariably involve high-energy and often toxic or cumbersome molecules to make the process exergonic. CO2 aminoalkylation using olefins and amines represents an attractive albeit endergonic alternative. We report a moisture-tolerant method that uses visible light energy to drive this endergonic process (+25 kcal/mol at STP) using sensitized arylcyclohexenes. They convert much of the photon's energy to strain upon olefin isomerization. This strain energy greatly enhances alkene basicity, allowing for sequential protonation by and interception of ammonium carbamates. Following optimization steps and amine scope evaluation, an example product arylcyclohexyl urethane underwent transcarbamoylation with some demonstrative alcohols to form more general urethanes with concomitant regeneration of the arylcyclohexene. This represents a closure of the energetic cycle, producing H2O as the stoichiometric byproduct.
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Affiliation(s)
- Timothy D Schoch
- Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Jimmie D Weaver
- Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States
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Lantz E, El Mokadem R, Schoch T, Fleske T, Weaver JD. A new twist for Stork-Danheiser products enabled by visible light mediated trans-cyclohexene formation; access to acyclic distal enones. Chem Sci 2022; 13:9271-9276. [PMID: 36093001 PMCID: PMC9384155 DOI: 10.1039/d1sc03774a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 07/03/2022] [Indexed: 11/21/2022] Open
Abstract
Herein, we investigate the use of visible light to indirectly drive ring opening in unstrained 6- and 7-membered ring systems via reaction with a transiently generated trans-cycloalkene. Identification of conditions that capture visible light energy in the form of ring strain was key to success. Under mildly acidic conditions, cycloalkenols were shown to undergo formally endothermic ring-opening isomerization to give acyclic exo-methylene and distal ketones or aldehydes in high yields. Ultimately, this work demonstrates the ability of cycloalkenes to capture visible light energy and its use to drive both kinetically and thermally unfavorable rearrangements.
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Affiliation(s)
- Erik Lantz
- 107 Physical Science, Department of Chemistry, Oklahoma State University Stillwater Oklahoma 74078 USA
| | | | - Tim Schoch
- 107 Physical Science, Department of Chemistry, Oklahoma State University Stillwater Oklahoma 74078 USA
| | - Tyler Fleske
- 107 Physical Science, Department of Chemistry, Oklahoma State University Stillwater Oklahoma 74078 USA
| | - Jimmie D Weaver
- 107 Physical Science, Department of Chemistry, Oklahoma State University Stillwater Oklahoma 74078 USA
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Day JI, Singh K, Trinh W, Weaver JD. Visible Light Mediated Generation of trans-Arylcyclohexenes and Their Utilization in the Synthesis of Cyclic Bridged Ethers. J Am Chem Soc 2018; 140:9934-9941. [DOI: 10.1021/jacs.8b04642] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Jon I. Day
- 107 Physical Science, Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Kamaljeet Singh
- 107 Physical Science, Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Winston Trinh
- 107 Physical Science, Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States
| | - Jimmie D. Weaver
- 107 Physical Science, Department of Chemistry, Oklahoma State University, Stillwater, Oklahoma 74078, United States
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Sandströum J. Static and Dynamic Stereochemistry of Push-Pull and Strained Ethylenes. TOPICS IN STEREOCHEMISTRY 2007. [DOI: 10.1002/9780470147238.ch2] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
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Abstract
In reexamining medium effects on photochemical reactions, we have emphasized those on unequilibrated excited species such as the Franck-Condon species. Despite recent advances in femtochemistry, such a discussion in molecular photochemistry is uncommon, and the problem remains challenging on account of the extremely short-lived excited species. However, in such cases, a small perturbation resulting from, for example, weak guest-host interactions could turn into a determining factor in dictating the course of a photochemical channel of deactivation. Examples of medium-directed diabatic processes have been examined with this idea in mind. A modified view on rhodopsin photoisomerization is presented along with the consideration that confinement does not necessarily lead to inhibition of reactions of the trapped substrate.
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Affiliation(s)
- Robert S H Liu
- Department of Chemistry, University of Hawaii, 2545 The Mall, Honolulu, Hawaii 96822, USA.
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Baldwin JE, Gallagher SS, Leber PA, Raghavan AS, Shukla R. Deuterium Kinetic Isotope Effects and Mechanism of the Thermal Isomerization of Bicyclo[4.2.0]oct-7-ene to 1,3-Cyclooctadiene. J Org Chem 2004; 69:7212-9. [PMID: 15471471 DOI: 10.1021/jo040220l] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The thermal conversion of cis-bicyclo[4.2.0]oct-7-ene to cis,cis-1,3-cyclooctadiene might involve a direct disrotatory ring opening, or it might possibly take place by way of cis,trans-1,3-cyclooctadiene. This cis,trans-diene might possibly form the more stable cis,cis isomer through a [1,5] hydrogen shift or a trans-to-cis isomerization about the trans double bond. Deuterium kinetic isotope effect determinations for the isomerizations of 2,2,5,5-d(4)-bicyclo[4.2.0]oct-7-ene and 7,8-d(2)-bicyclo[4.2.0]oct-7-ene rule out these two alternatives because the observed effects are much smaller than would be anticipated for these mechanisms: k(H)/k(D)(d(4)) at 250 degrees C is 1.17 (1.04 per D), and k(H)/k(D)(d(2)) at 238 degrees C is 1.20 (1.10 per D). The direct disrotatory ring opening route remains the preferred mechanism.
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Affiliation(s)
- John E Baldwin
- Department of Chemistry, Syracuse University, Syracuse, New York 13244, USA.
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11
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Shim SC, Kim DS, Yoo DJ, Wada T, Inoue Y. Diastereoselectivity control in photosensitized addition of methanol to (R)-(+)-limonene. J Org Chem 2002; 67:5718-26. [PMID: 12153274 DOI: 10.1021/jo025782o] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Highly diastereodifferentiating bimolecular asymmetric photoreaction was achieved in the photosensitized polar addition of methanol to (R)-(+)-limonene. The diastereomeric excess (de) of the photoadduct could be controlled and fine-tuned by changing the internal/external factors such as solvent polarity, reaction temperature, and structure of the sensitizers. The de increased from 23% obtained upon xylene photosensitization in pure methanol at room temperature to >96% upon singlet sensitization with methyl benzoate at -75 degrees C in 0.5 M methanol/diethyl ether solution.
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Affiliation(s)
- Sang Chul Shim
- Center for Molecular Design and Synthesis, Department of Chemistry and School of Molecular Science (BK-21), Korea Advanced Institute of Science and Technology (KAIST), 373-1 Guseong-Dong, Yuseong-Gu, Daejeon 305-701, Korea.
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12
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Nekipelova TD. Mechanism of the photoinduced addition of methanol to the double bond of 2,2,4,6-tetramethyl- and 1,2,2,4,6-pentamethyl-1,2-dihydroquinolines. Photochem Photobiol Sci 2002; 1:204-10. [PMID: 12659518 DOI: 10.1039/b110113g] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The mechanism of the photoinduced Markovnikov addition of methanol to the double bond of 2,2,4,6-tetramethyl-1,2-dihydroquinoline (1) and 1,2,2,4,6-pentamethyl-1,2-dihydroquinoline (2) was studied by the flash photolysis technique over a wide range of acetic acid and KOH concentrations. The successive formation of two transients was observed in neutral solutions in the case of compound 1. These transients have lifetimes on ms time-scales and absorption spectra with maxima at 420 and 480 nm for the first and the second transient, respectively. The decay rate constants of these transients (k1 and k2) were measured over the temperature range from 10 to 45 degrees C and the activation energies E1 approximately 0 and E2 (31.4 +/- 3.1) kJ mol(-1) were determined. In MeOH acidified with acetic acid only the second transient (lambda(max) = 480 nm) was observed, and it is proposed that this is due to a carbocation. The deuterium kinetic isotope effects determined in MeOD are 2 and 1.3 for k1 and k2, respectively, indicating that the first reaction is proton transfer proceeding via the A-SE2 mechanism and the second reaction is the nucleophilic addition of the solvent to the carbocation. In alkaline media, only the first transient (lambda(max) = 420 nm) was observed with a lifetime of 250 ms at [KOH] > 2 x 10(-3) mol dm(-3). In the case of compound 2, the formation of a carbocation with lambda(max) = 490 mn and a lifetime of several ms is observed within 10 ns of excitation in neutral, acidic, and alkaline solutions. The carbocation is quenched with KOH with a rate constant of 7 x 10(6) mol(-1) dm(3) s(-1). The quantum yields of the reaction and of the fluorescence were measured and possible mechanisms discussed.
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Affiliation(s)
- Tatiana D Nekipelova
- Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, 4 Kosygin str., Moscow, 119991, Russia.
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Fuss W, Schmid WE, Trushin SA. Ultrafast dynamics of cyclohexene and cyclohexene-d10 excited at 200 nm. J Am Chem Soc 2001; 123:7101-8. [PMID: 11459489 DOI: 10.1021/ja004115e] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
By exciting cyclohexene in the gas phase at 200 nm and probing it by nonresonant multiphoton ionization with mass-selective detection of the ion yields, we found four time constants tau(i) (20, 47, 43, 350 fs). Whereas deuteration lengthens tau2 by a factor of 1.4, the other constants do not change. Tau1-tau3 represent traveling times through observation windows on excited surfaces, whereas tau4 reflects a process in the hot ground state. We assign tau1 (20 fs) to departure from the Franck-Condon regions of the Rydberg and pipi* states, which are both populated at 200 nm, and tau2 (47 fs) to traveling along the pipi* surface and suggest that a [1,3]-sigmatropic H shift begins in this state. This rationalizes the deuterium effect on tau2. To explain why this window is followed by a process not subject to a D effect, we postulate that the pipi surface is crossed late (i.e., at low energy) by the zwitterionic state Z and that formation of a carbene (the known photochemical product, cyclopentylcarbene) begins there. The corresponding 1,2-shift of a CC bond is then (within tau4 = 350 fs) largely reversed on the ground-state surface, while a smaller part of the carbene forms products such as methylenecyclopentane within the same time. Carbene formation is probably accompanied by some cis-trans isomerization. The wavelength dependence of carbene formation is attributed to a memory for the initially excited state, based on momentum conservation. The processes are most likely typical of simple olefins. The fragmentation pattern showed that butadiene is not formed until at least 500 ps. The retro-Diels-Alder reaction, known to take place in the ground state, thus only occurs later.
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Affiliation(s)
- W Fuss
- Max-Planck-Institut für Quantenoptik, D-85741 Garching, Germany
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Woeller M, Grimme S, Peyerimhoff SD, Danovich D, Filatov M, Shaik S. A Theoretical Study of the Radiationless Decay Mechanism of Cyclic Alkenes in the Lowest Triplet State. J Phys Chem A 2000. [DOI: 10.1021/jp0003398] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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15
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Smith RE, Richards NGJ. Importance of Steric Effects in the Photochemical Ring Opening of Isochromenes. J Org Chem 1997. [DOI: 10.1021/jo961496z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Richard E. Smith
- Department of Chemistry, University of Florida, Gainesville, Florida 32611
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Herbertz T, Roth HD. Electron Transfer Photochemistry of Chrysanthemol: An Intramolecular SN2‘ Reaction of a Vinylcyclopropane Radical Cation. J Am Chem Soc 1996. [DOI: 10.1021/ja953596c] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Torsten Herbertz
- Contribution from the Department of Chemistry, Rutgers University, Wright-Rieman Laboratories, New Brunswick, New Jersey 08855-0939
| | - Heinz D. Roth
- Contribution from the Department of Chemistry, Rutgers University, Wright-Rieman Laboratories, New Brunswick, New Jersey 08855-0939
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Unett DJ, Caldwell RA, Hrncir DC. Photodimerization of 1-Phenylcyclohexene. A Novel Transient−Transient Component. J Am Chem Soc 1996. [DOI: 10.1021/ja9533860] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- David J. Unett
- Contribution from the Department of Chemistry, The University of Texas at Dallas, Richardson, Texas 75083
| | - Richard A. Caldwell
- Contribution from the Department of Chemistry, The University of Texas at Dallas, Richardson, Texas 75083
| | - Duane C. Hrncir
- Contribution from the Department of Chemistry, The University of Texas at Dallas, Richardson, Texas 75083
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McGarry PF, Cheh J, Ruiz-Silva B, Hu S, Wang J, Nakanishi K, Turro NJ. A Laser Flash Photolysis Study of 11-Cis-Locked Retinal Analogues. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp9518769] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Peter F. McGarry
- Department of Chemistry, Columbia University, New York, New York 10027
| | - James Cheh
- Department of Chemistry, Columbia University, New York, New York 10027
| | | | - Shuanghua Hu
- Department of Chemistry, Columbia University, New York, New York 10027
| | - Jun Wang
- Department of Chemistry, Columbia University, New York, New York 10027
| | - Koji Nakanishi
- Department of Chemistry, Columbia University, New York, New York 10027
| | - Nicholas J. Turro
- Department of Chemistry, Columbia University, New York, New York 10027
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Schuster DI, Yang JM, Woning J, Rhodes TA, Jensen AW. Mechanism of acid-catalyzed photoaddition of methanol to 3-alkyl2-cyclohexenones. CAN J CHEM 1995. [DOI: 10.1139/v95-247] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Contrary to a previous report, it is concluded that formation of methanol adducts to 3-methyl-2-cyclohexenones and of deconjugated enones on irradiation of the enones in acidified solutions proceeds via protonation of the intermediate enone π,π* triplet excited state and not by protonation of a relatively long-lived ground state trans-cyclohexenone. A rate constant for protonation of the triplet state of 3-methyl-2-cyclohexenone by sulfuric acid of 1.7 × 109 M−1 s−1 was determined by laser flash photolysis in ethyl acetate. Based on quantum efficiencies of product formation, a rate constant of ca. 108 M−1 s−1 was estimated for protonation of the enone triplet by acetic acid, which is too small to cause measurable reduction in the triplet state lifetime in the mM concentration range used in the preparative studies. The intermediate carbocation can be trapped by methanol, or revert to starting enone or the exocyclic deconjugated enone by loss of a proton. Since products revert to starting materials in an acid-catalyzed process, there is an acid concentration at which the yields of products are optimal. This concentration is ca. 6 mM for acetic acid, but is only 0.1 mM for p-toluenesulfonic or sulfuric acids. Product formation could be quenched using 1-methylnaphthalene and cyclopentene as triplet quenchers; in the latter case, formation of [2 + 2] photoadducts was observed to compete with formation of methanol adducts. Quenching rate constants were determined by laser flash studies. Keywords: laser flash photolysis, kinetic absorption spectroscopy (KAS), photoacoustic calorimetry (PAC), protonation of triplet states, trans-cyclohexenones.
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BRENNAN COLINM, CALDWELL RICHARDA. PHOTOACOUSTIC CALORIMETRY OF CYCLOHEPTENE DERIVATIVES. RELAXED TRIPLET ENERGIES OF 1-PHENYLCYCLOHEPTENE AND 1, 3-CYCLOHEPTADIENE AND THE ENERGETICS OF GROUND-STATE cis-trans ISOMERIZATION. Photochem Photobiol 1991. [DOI: 10.1111/j.1751-1097.1991.tb03918.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Affiliation(s)
- Y Shichida
- Department of Biophysics, Faculty of Science, Kyoto University, Japan
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Mintas M, Schuster DI, Williard PG. Stereochemistry and mechanism of the [2 + 2] and [4 + 2] photocycloaddition of alkenes and dienes to pummerer's ketone. Tetrahedron 1988. [DOI: 10.1016/s0040-4020(01)89788-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Kojima M, Sakuragi H, Tokumaru K. Photochemical Reactions of Contact Charge-Transfer Pairs of 1-Arylcyclohexenes and Oxygen. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 1987. [DOI: 10.1246/bcsj.60.3331] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Bonneau R. Some new examples of “trans” cyclohexenes: properties characteristic of these species. ACTA ACUST UNITED AC 1987. [DOI: 10.1016/0047-2670(87)80022-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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cis,trans-1,1′-bicyclohexenyl: a strained ground state intermediate in the photocyclization of 1,1′-bicyclohexenyl to its isomeric cis-cyclobutene. ACTA ACUST UNITED AC 1985. [DOI: 10.1016/0047-2670(85)85038-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Photochemical Rearrangements of Enones. ACTA ACUST UNITED AC 1980. [DOI: 10.1016/b978-0-12-481303-8.50010-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2023]
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Havrilla GJ, Goldfarb TD. Matrix photolysis of cis, cis-1,3-cycloheptadiene: evidence for the existence of the highly strained cis, trans isomer. ACTA ACUST UNITED AC 1979. [DOI: 10.1016/0047-2670(79)80023-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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32
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Kinetic studies of transient photochemical isomers of 2-cycloheptenone, 1-acetylcyclohexene and 2-cyclohexenone. ACTA ACUST UNITED AC 1978. [DOI: 10.1016/0047-2670(78)80004-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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33
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Sakuragi M, Sakuragi H, Hasegawa M. Photochemistry of 1,2-Diphenylcyclobutene in Protic Solvents. Addition of Alcohols, Acetic Acid, and Water. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 1977. [DOI: 10.1246/bcsj.50.1562] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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34
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Bonneau R, Joussot-Dubien J, Yarwood J, Pereyre J. Spectre electronique de la forme “trans” du phenyl-1 cycloheptene. Tetrahedron Lett 1977. [DOI: 10.1016/s0040-4039(01)92599-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Evidence and Reactivity of a Twisted Form of Medium Size Cycloalkene Rings Presenting a Double Bond Past Orthogonality. ACTA ACUST UNITED AC 1977. [DOI: 10.1007/978-94-010-1273-7_23] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Gisin M, Wirz J. Photolysis of the azo-precursors of 2,3- and 1,8-naphtoquinodimethane. Preliminary communication. Helv Chim Acta 1976. [DOI: 10.1002/hlca.19760590644] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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