Asymmetric nucleophilic substitutions to construct all-carbon quaternary stereocenters under PTC conditions
Nucleophilicity and nucleophilic substitution is one of the most important concepts and processes in organic chemistry. Traditionally, the term nucleophilic substitution in organic chemistry implies substitution exactly at the carbon atom, but there is a rather wide class of reactions in which the n...
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| Format: | Thesis |
| Language: | English |
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2019
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| Online Access: | https://hdl.handle.net/10356/83133 http://hdl.handle.net/10220/47585 |
| _version_ | 1826112500924416000 |
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| author | Ban, Xu |
| author2 | Tan Choon Hong |
| author_facet | Tan Choon Hong Ban, Xu |
| author_sort | Ban, Xu |
| collection | NTU |
| description | Nucleophilicity and nucleophilic substitution is one of the most important concepts and processes in organic chemistry. Traditionally, the term nucleophilic substitution in organic chemistry implies substitution exactly at the carbon atom, but there is a rather wide class of reactions in which the nucleophile attacks a halogen atom but not the carbon atom, such reactions, then are named halophilic or halogenophilic reactions and proceeded by SNX route.
Herein we describe a novel asymmetric nucleophilic substitution to construct all-carbon quaternary stereocenters under PTC conditions. In this reaction, the C-Br bond is cleaved to generate a newly C-C bond with high enantioselectivity. Different kinds of tertiary bromides with electron withdrawing groups are proved to be excellent electrophiles for malonates under a base condition. We envisioned that the breakthrough of the C-halogen bond is proceed by a SNX route and our guanidiniums PTC induce the formation of the all carbon quaternary canter. This concept provide a new direction for the development of nucleophilic substitutions. |
| first_indexed | 2024-10-01T03:08:04Z |
| format | Thesis |
| id | ntu-10356/83133 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T03:08:04Z |
| publishDate | 2019 |
| record_format | dspace |
| spelling | ntu-10356/831332023-02-28T23:35:04Z Asymmetric nucleophilic substitutions to construct all-carbon quaternary stereocenters under PTC conditions Ban, Xu Tan Choon Hong School of Physical and Mathematical Sciences DRNTU::Science::Chemistry::Organic chemistry Nucleophilicity and nucleophilic substitution is one of the most important concepts and processes in organic chemistry. Traditionally, the term nucleophilic substitution in organic chemistry implies substitution exactly at the carbon atom, but there is a rather wide class of reactions in which the nucleophile attacks a halogen atom but not the carbon atom, such reactions, then are named halophilic or halogenophilic reactions and proceeded by SNX route. Herein we describe a novel asymmetric nucleophilic substitution to construct all-carbon quaternary stereocenters under PTC conditions. In this reaction, the C-Br bond is cleaved to generate a newly C-C bond with high enantioselectivity. Different kinds of tertiary bromides with electron withdrawing groups are proved to be excellent electrophiles for malonates under a base condition. We envisioned that the breakthrough of the C-halogen bond is proceed by a SNX route and our guanidiniums PTC induce the formation of the all carbon quaternary canter. This concept provide a new direction for the development of nucleophilic substitutions. Doctor of Philosophy 2019-01-30T02:15:21Z 2019-12-06T15:12:25Z 2019-01-30T02:15:21Z 2019-12-06T15:12:25Z 2019 Thesis Ban, X. (2019). Asymmetric nucleophilic substitutions to construct all-carbon quaternary stereocenters under PTC conditions. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/83133 http://hdl.handle.net/10220/47585 10.32657/10220/47585 en 241 p. application/pdf |
| spellingShingle | DRNTU::Science::Chemistry::Organic chemistry Ban, Xu Asymmetric nucleophilic substitutions to construct all-carbon quaternary stereocenters under PTC conditions |
| title | Asymmetric nucleophilic substitutions to construct all-carbon quaternary stereocenters under PTC conditions |
| title_full | Asymmetric nucleophilic substitutions to construct all-carbon quaternary stereocenters under PTC conditions |
| title_fullStr | Asymmetric nucleophilic substitutions to construct all-carbon quaternary stereocenters under PTC conditions |
| title_full_unstemmed | Asymmetric nucleophilic substitutions to construct all-carbon quaternary stereocenters under PTC conditions |
| title_short | Asymmetric nucleophilic substitutions to construct all-carbon quaternary stereocenters under PTC conditions |
| title_sort | asymmetric nucleophilic substitutions to construct all carbon quaternary stereocenters under ptc conditions |
| topic | DRNTU::Science::Chemistry::Organic chemistry |
| url | https://hdl.handle.net/10356/83133 http://hdl.handle.net/10220/47585 |
| work_keys_str_mv | AT banxu asymmetricnucleophilicsubstitutionstoconstructallcarbonquaternarystereocentersunderptcconditions |