How an early or late transition state impacts the stereoselectivity of tetrahydropyran formation by intramolecular oxa-Michael addition
The intramolecular oxa-Michael addition giving tetrahydropyrans has been examined experimentally using both acidic and basic catalysis. With acidic catalysis, the diequatorial product is exclusively obtained in a kinetically controlled reaction in all cases. Under basic conditions at low temperature...
| Main Authors: | , , , |
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| Format: | Journal Article |
| Language: | English |
| Published: |
2020
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| Online Access: | https://hdl.handle.net/10356/141244 |
| _version_ | 1811680172408045568 |
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| author | Csókás, Dániel Ho, Annabel Xuan Ying Ramabhadran, Raghunath O. Bates, Roderick Wayland |
| author2 | School of Physical and Mathematical Sciences |
| author_facet | School of Physical and Mathematical Sciences Csókás, Dániel Ho, Annabel Xuan Ying Ramabhadran, Raghunath O. Bates, Roderick Wayland |
| author_sort | Csókás, Dániel |
| collection | NTU |
| description | The intramolecular oxa-Michael addition giving tetrahydropyrans has been examined experimentally using both acidic and basic catalysis. With acidic catalysis, the diequatorial product is exclusively obtained in a kinetically controlled reaction in all cases. Under basic conditions at low temperature, the reaction is again under kinetic control, but formation of the axial-equatorial isomer is generally favoured with an (E)-Michael acceptor, although isomerisation to the diequatorial isomer is observed at higher temperatures. Computationally, it is found that the acid catalysed reaction has a late transition state and the kinetic favouring of the diequatorial isomer has a steric explanation. In contrast, under strongly basic conditions, an early transition state is found. Electrostatic effects are likely to be the main contributor to the stereoselectivity for the (E)-isomer and steric interactions for the (Z)-isomer. |
| first_indexed | 2024-10-01T03:20:49Z |
| format | Journal Article |
| id | ntu-10356/141244 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T03:20:49Z |
| publishDate | 2020 |
| record_format | dspace |
| spelling | ntu-10356/1412442023-02-28T19:50:10Z How an early or late transition state impacts the stereoselectivity of tetrahydropyran formation by intramolecular oxa-Michael addition Csókás, Dániel Ho, Annabel Xuan Ying Ramabhadran, Raghunath O. Bates, Roderick Wayland School of Physical and Mathematical Sciences Science::Chemistry Oxa-Michael Addition Stereoselectivity The intramolecular oxa-Michael addition giving tetrahydropyrans has been examined experimentally using both acidic and basic catalysis. With acidic catalysis, the diequatorial product is exclusively obtained in a kinetically controlled reaction in all cases. Under basic conditions at low temperature, the reaction is again under kinetic control, but formation of the axial-equatorial isomer is generally favoured with an (E)-Michael acceptor, although isomerisation to the diequatorial isomer is observed at higher temperatures. Computationally, it is found that the acid catalysed reaction has a late transition state and the kinetic favouring of the diequatorial isomer has a steric explanation. In contrast, under strongly basic conditions, an early transition state is found. Electrostatic effects are likely to be the main contributor to the stereoselectivity for the (E)-isomer and steric interactions for the (Z)-isomer. Accepted version 2020-06-05T04:43:25Z 2020-06-05T04:43:25Z 2019 Journal Article Csókás, D., Ho, A. X. Y., Ramabhadran, R. O., & Bates, R. W. (2019). How an early or late transition state impacts the stereoselectivity of tetrahydropyran formation by intramolecular oxa-Michael addition. Organic & Biomolecular Chemistry, 17(25), 6293-6304. doi:10.1039/C9OB00750D 1477-0520 https://hdl.handle.net/10356/141244 10.1039/C9OB00750D 25 17 6293 6304 en Organic & Biomolecular Chemistry © 2019 The Royal Society of Chemistry. All rights reserved. This paper was published in Organic & Biomolecular Chemistry and is made available with permission of The Royal Society of Chemistry. application/pdf |
| spellingShingle | Science::Chemistry Oxa-Michael Addition Stereoselectivity Csókás, Dániel Ho, Annabel Xuan Ying Ramabhadran, Raghunath O. Bates, Roderick Wayland How an early or late transition state impacts the stereoselectivity of tetrahydropyran formation by intramolecular oxa-Michael addition |
| title | How an early or late transition state impacts the stereoselectivity of tetrahydropyran formation by intramolecular oxa-Michael addition |
| title_full | How an early or late transition state impacts the stereoselectivity of tetrahydropyran formation by intramolecular oxa-Michael addition |
| title_fullStr | How an early or late transition state impacts the stereoselectivity of tetrahydropyran formation by intramolecular oxa-Michael addition |
| title_full_unstemmed | How an early or late transition state impacts the stereoselectivity of tetrahydropyran formation by intramolecular oxa-Michael addition |
| title_short | How an early or late transition state impacts the stereoselectivity of tetrahydropyran formation by intramolecular oxa-Michael addition |
| title_sort | how an early or late transition state impacts the stereoselectivity of tetrahydropyran formation by intramolecular oxa michael addition |
| topic | Science::Chemistry Oxa-Michael Addition Stereoselectivity |
| url | https://hdl.handle.net/10356/141244 |
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