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Deslongchamps P. A new mechanism for the thermal and photochemical Diels-Alder cycloaddition based on the bent bond / antiperiplanar hypothesis orbital model. J Mol Struct 2022. [DOI: 10.1016/j.molstruc.2022.133288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Stereochemistry of Eʹ and Eʹʹ decarboxylative-dehydration reactions and the bent bond / antiperiplanar hypothesis orbital model. Tetrahedron 2021. [DOI: 10.1016/j.tet.2021.132538] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Revisiting the conformational analysis of unsaturated organic compounds using the bent bond / antiperiplanar hypothesis. Tetrahedron 2021. [DOI: 10.1016/j.tet.2021.132249] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Deslongchamps P. Bent bond / antiperiplanar hypothesis and antiaromatic, aromatic and nonaromatic molecules. Tetrahedron 2021. [DOI: 10.1016/j.tet.2021.132161] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Deslongchamps P. The conformation and reactivity of butadiene and the bent bond/antiperiplanar hypothesis orbital model. Tetrahedron 2021. [DOI: 10.1016/j.tet.2021.132060] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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The thermal rearrangements of naphthalene and azulene. An analysis through the bent bond and antiperiplanar hypothesis orbital model. Tetrahedron 2021. [DOI: 10.1016/j.tet.2021.131956] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Deslongchamps P. The bent bond / antiperiplanar hypothesis and the thermal rearrangement of cyclopropyl halides and tosylates. Tetrahedron 2020. [DOI: 10.1016/j.tet.2020.131416] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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Deslongchamps G, Deslongchamps P. Bent Bond/Antiperiplanar Hypothesis and the Chemical Reactivity of Annulenes. J Org Chem 2020; 85:8645-8655. [PMID: 32501012 DOI: 10.1021/acs.joc.0c01069] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The properties and stereochemical reactivity of cyclobutadiene, benzene, cyclooctatetraene, and the [10]- to [14]annulenes can be uniformly rationalized through the bent bond/antiperiplanar hypothesis (BBAH). This new orbital model considers electronic delocalization between pyramidal diradical resonance structures and associated bent bonds, as it applies to aromatic, nonaromatic, and antiaromatic molecules.
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Affiliation(s)
- Ghislain Deslongchamps
- Department of Chemistry, University of New Brunswick, P.O. Box 4400, Fredericton, New Brunswick E3B 5A3, Canada
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Parent JF, Deslongchamps G, Deslongchamps P. Bent Bond/Antiperiplanar Hypothesis: Modulating the Reactivity and the Selectivity in the Glycosylation of Bicyclic Pyranoside Models. J Org Chem 2020; 85:4220-4236. [PMID: 32068401 DOI: 10.1021/acs.joc.9b03412] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Glycosylation reactions were performed on a series of bicyclic C2-substituted pyranoside models to isolate and analyze factors that control the glycosylation stereoselectivities observed in carbohydrates. The bent bond/antiperiplanar hypothesis (BBAH) orbital model rationalizes all of these results by considering hyperconjugation interactions between groups at C2 and the two τ bonds (bent bonds) of oxocarbenium ion intermediates formed under the glycosylation conditions. According to the BBAH, nucleophiles add to oxocarbenium intermediates by SN2-like antiperiplanar displacement of the weaker of their two τ bonds.
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Parent JF, Bertrand X, Deslongchamps G, Deslongchamps P. Applying the Bent Bond/Antiperiplanar Hypothesis to the Stereoselective Glycosylation of Bicyclic Furanosides. J Org Chem 2020; 85:758-773. [PMID: 31820643 DOI: 10.1021/acs.joc.9b02791] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The glycosylation stereoselectivities for a series of bicyclic furanoside models have been carried out in the presence of weak nucleophiles. These results were analyzed through the bent bond/antiperiplanar hypothesis (BBAH) orbital model to test its validity. According to the BBAH, incoming nucleophiles displace one of the two bent bonds of bicyclic oxocarbenium ion intermediates in an antiperiplanar fashion. The glycosylation stereoselectivity is then governed by the displacement of the weaker bent bond as determined by the presence of electron-withdrawing or -donating substituents at C2. Overall, the BBAH analysis expands Woerpel's "inside/outside attack" glycosylation model by considering the stereoelectronic influence of neighboring electron-withdrawing and -donating groups on the nucleophilic addition to oxocarbenium ion intermediates.
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Affiliation(s)
| | - Xavier Bertrand
- Département de Chimie , Université Laval , Québec , QC G1V 0A6 , Canada
| | - Ghislain Deslongchamps
- Department of Chemistry , University of New Brunswick , Fredericton , NB E3B 5A3 , Canada
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Deslongchamps G, Deslongchamps P. Thermal rearrangement of optically active tetradeuterated 2-methoxymethyl-methylenecyclopropane and the bent bond/antiperiplanar hypothesis. Org Biomol Chem 2019; 17:7007-7012. [PMID: 31282912 DOI: 10.1039/c9ob01030k] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The thermolysis of an optically active tetradeuterated 2-methoxymethyl methylenecyclopropane produces a specific ratio of eight possible rearrangement stereoisomers. Despite numerous efforts, this reaction and other similar transformations have defied mechanistic interpretation until now. The direct application of the bent bond/antiperiplanar hypothesis (BBAH) to this reaction produces a mechanistic model that rationalizes all the observed reaction kinetics and products. The BBAH dictates that allyl diradical intermediates, produced during methylenecyclopropane thermolysis, retain pyramidal character due to antiperiplanar delocalization into their respective bent bond.
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Affiliation(s)
- Ghislain Deslongchamps
- Department of Chemistry, University of New Brunswick, P. O. Box 4400, Fredericton, NB E3B 5A3, Canada.
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Deslongchamps G, Deslongchamps P. Bent Bonds and the Antiperiplanar Hypothesis. A Model To Account for Sigmatropic [1, n]-Hydrogen Shifts. J Org Chem 2018; 83:10383-10388. [PMID: 30041522 DOI: 10.1021/acs.joc.8b01472] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The bent bond/antiperiplanar hypothesis (BBAH) is used to propose a mechanism-based orbital model for the facial selectivity of sigmatropic hydrogen shifts under both thermal and photochemical conditions. The BBAH analysis of these concerted rearrangements invokes transient vibrationally excited singlet diradicals in both 4 n and 4 n+2 polyenes.
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Affiliation(s)
- Ghislain Deslongchamps
- Department of Chemistry , University of New Brunswick , Fredericton , New Brunswick E3B 5A3 , Canada
| | - Pierre Deslongchamps
- Département de Chimie , Université Laval , Québec City , Québec G1V 0A6 , Canada
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Deslongchamps G, Deslongchamps P. Bent Bonds (τ) and the Antiperiplanar Hypothesis-The Chemistry of Cyclooctatetraene and Other C 8H 8 Isomers. J Org Chem 2018; 83:5751-5755. [PMID: 29715429 DOI: 10.1021/acs.joc.8b00809] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The bent bond/antiperiplanar hypothesis (BBAH) has been applied to the thermal rearrangements of cyclooctatetraene and related C8H8 isomers. This novel orbital model shows that pyramidal singlet diradical intermediates produced from thermal vibrational states of C8H8 isomers account for their chemical reactivity.
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Affiliation(s)
- Ghislain Deslongchamps
- Department of Chemistry , University of New Brunswick , Fredericton , NB , E3B 5A3 , Canada
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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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Parent JF, Deslongchamps P. Bent bonds (τ) and the antiperiplanar hypothesis, and the reactivity at the anomeric center in pyranosides. Org Biomol Chem 2018; 14:11183-11198. [PMID: 27834970 DOI: 10.1039/c6ob02263d] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The stereoselectivity of nucleophilic addition on oxocarbenium ions derived from the bicyclic pyranoside model with or without a C2-OR group can be understood through the use of the bent-bond and the antiperiplanar hypothesis in conjunction with the concept of hyperconjugation as an alternative interpretive model of structure and reactivity.
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Affiliation(s)
- Jean-François Parent
- Département de chimie, Faculté des sciences et de génie, Université Laval, Pavillon Alexandre-Vachon, 1045 avenue de la médecine, Québec, Québec G1V 0A6, Canada.
| | - Pierre Deslongchamps
- Département de chimie, Faculté des sciences et de génie, Université Laval, Pavillon Alexandre-Vachon, 1045 avenue de la médecine, Québec, Québec G1V 0A6, Canada.
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