Bromination of endo-7-norbornene derivatives revisited: failure of a computational NMR method in elucidating the configuration of an organic structure
Previously we reported on the bromination of endo-7-bromonorbornene at different temperatures yielding mixtures of addition products. The structural elucidations of the formed compounds were achieved by NMR spectroscopy. Particularly, the γ-gauche effect and long-range couplings were instrumental in...
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| Format: | Article |
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Beilstein-Institut
2023-06-01
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| Series: | Beilstein Journal of Organic Chemistry |
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| Online Access: | https://doi.org/10.3762/bjoc.19.56 |
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| author | Demet Demirci Gültekin Arif Daştan Yavuz Taşkesenligil Cavit Kazaz Yunus Zorlu Metin Balci |
| author_facet | Demet Demirci Gültekin Arif Daştan Yavuz Taşkesenligil Cavit Kazaz Yunus Zorlu Metin Balci |
| author_sort | Demet Demirci Gültekin |
| collection | DOAJ |
| description | Previously we reported on the bromination of endo-7-bromonorbornene at different temperatures yielding mixtures of addition products. The structural elucidations of the formed compounds were achieved by NMR spectroscopy. Particularly, the γ-gauche effect and long-range couplings were instrumental in assigning the stereochemistry of the adducts. However, in a recent paper, Novitskiy and Kutateladze claimed that based on an applied machine learning-augmented DFT method for computational NMR that the structure of the product, (1R,2R,3S,4S,7s)-2,3,7-tribromobicyclo[2.2.1]heptane was wrong. With the aid of their computational method, they revised a number of published structures, including ours, and assigned our product the structure (1R,2S,3R,4S,7r)-2,3,7-tribromobicyclo[2.2.1]heptane. To fit their revised structure, they proposed an alternative mechanism featuring a skeletal rearrangement without the intermediacy of a carbocation. Herein, we are not only confirming the structure originally assigned by us through crucial NMR experiments, we also present the ultimate structural proof by means of X-ray crystallography. Moreover, we disprove the mechanism proposed by the aforementioned authors based on sound mechanistic reasoning and point to an oversight by the authors that led them to an erroneous mechanistic pathway. |
| first_indexed | 2024-03-13T06:54:29Z |
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| institution | Directory Open Access Journal |
| issn | 1860-5397 |
| language | English |
| last_indexed | 2024-03-13T06:54:29Z |
| publishDate | 2023-06-01 |
| publisher | Beilstein-Institut |
| record_format | Article |
| series | Beilstein Journal of Organic Chemistry |
| spelling | doaj.art-1a3f061d12cf4d0982d634bdd733f1bf2023-06-07T12:01:23ZengBeilstein-InstitutBeilstein Journal of Organic Chemistry1860-53972023-06-0119176477010.3762/bjoc.19.561860-5397-19-56Bromination of endo-7-norbornene derivatives revisited: failure of a computational NMR method in elucidating the configuration of an organic structureDemet Demirci Gültekin0Arif Daştan1Yavuz Taşkesenligil2Cavit Kazaz3Yunus Zorlu4Metin Balci5Askale Vocational College, Department of Metallurgical Program, Atatürk University 25500 Erzurum, Turkey Department of Chemistry, Atatürk University, 25240 Erzurum, Turkey Faculty of Education, Atatürk University, 25240 Erzurum, Turkey Department of Chemistry, Atatürk University, 25240 Erzurum, Turkey Department of Chemistry, Gebze Technical University, 41400, Gebze, Turkey Department of Chemistry, Middle East Technical University, 06800 Ankara, Turkey Previously we reported on the bromination of endo-7-bromonorbornene at different temperatures yielding mixtures of addition products. The structural elucidations of the formed compounds were achieved by NMR spectroscopy. Particularly, the γ-gauche effect and long-range couplings were instrumental in assigning the stereochemistry of the adducts. However, in a recent paper, Novitskiy and Kutateladze claimed that based on an applied machine learning-augmented DFT method for computational NMR that the structure of the product, (1R,2R,3S,4S,7s)-2,3,7-tribromobicyclo[2.2.1]heptane was wrong. With the aid of their computational method, they revised a number of published structures, including ours, and assigned our product the structure (1R,2S,3R,4S,7r)-2,3,7-tribromobicyclo[2.2.1]heptane. To fit their revised structure, they proposed an alternative mechanism featuring a skeletal rearrangement without the intermediacy of a carbocation. Herein, we are not only confirming the structure originally assigned by us through crucial NMR experiments, we also present the ultimate structural proof by means of X-ray crystallography. Moreover, we disprove the mechanism proposed by the aforementioned authors based on sound mechanistic reasoning and point to an oversight by the authors that led them to an erroneous mechanistic pathway.https://doi.org/10.3762/bjoc.19.56brominationcomputational nmrγ-gauche effectnmrnoe-diff experiments |
| spellingShingle | Demet Demirci Gültekin Arif Daştan Yavuz Taşkesenligil Cavit Kazaz Yunus Zorlu Metin Balci Bromination of endo-7-norbornene derivatives revisited: failure of a computational NMR method in elucidating the configuration of an organic structure Beilstein Journal of Organic Chemistry bromination computational nmr γ-gauche effect nmr noe-diff experiments |
| title | Bromination of endo-7-norbornene derivatives revisited: failure of a computational NMR method in elucidating the configuration of an organic structure |
| title_full | Bromination of endo-7-norbornene derivatives revisited: failure of a computational NMR method in elucidating the configuration of an organic structure |
| title_fullStr | Bromination of endo-7-norbornene derivatives revisited: failure of a computational NMR method in elucidating the configuration of an organic structure |
| title_full_unstemmed | Bromination of endo-7-norbornene derivatives revisited: failure of a computational NMR method in elucidating the configuration of an organic structure |
| title_short | Bromination of endo-7-norbornene derivatives revisited: failure of a computational NMR method in elucidating the configuration of an organic structure |
| title_sort | bromination of endo 7 norbornene derivatives revisited failure of a computational nmr method in elucidating the configuration of an organic structure |
| topic | bromination computational nmr γ-gauche effect nmr noe-diff experiments |
| url | https://doi.org/10.3762/bjoc.19.56 |
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