Reactivity of anodically-generated methoxystilbene cation radicals: The effect of ortho’-substitution / Chong Kam Weng
A systematic study was undertaken to determine the influence of ortho-substituted nucleophilic (OH, NH2, CH2OH, CH2NHR, CO2H, CH=CH2) and non-nucleophilic (OMe, OAc, CN, NO2, CF3, CO2Me, CONH2, CHO) groups on the reactivity of anodically generated 4-methoxy- and 3,4-dimethoxystilbene cation radical...
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| Format: | Thesis |
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2019
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| Online Access: | http://studentsrepo.um.edu.my/12700/ http://studentsrepo.um.edu.my/12700/1/Chong_Kam_Weng.pdf http://studentsrepo.um.edu.my/12700/2/Chong_Kam_Weng.pdf |
| _version_ | 1848774714048118784 |
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| author | Chong , Kam Weng |
| author_facet | Chong , Kam Weng |
| author_sort | Chong , Kam Weng |
| building | UM Research Repository |
| collection | Online Access |
| description | A systematic study was undertaken to determine the influence of ortho-substituted nucleophilic (OH, NH2, CH2OH, CH2NHR, CO2H, CH=CH2) and non-nucleophilic (OMe, OAc, CN, NO2, CF3, CO2Me, CONH2, CHO) groups on the reactivity of anodically generated 4-methoxy- and 3,4-dimethoxystilbene cation radicals. The results showed that when ortho-substituted nucleophilic groups such as OH or NHR are directly attached to the aromatic ring, both direct and crossover intramolecular cation-nucleophile reactions occur to give bisbenzofurans/bisindoles or fused bisbenzopyrans/bisquinolines, respectively. When the ortho'-substituted side chains have been extended to include an intervening CH2 group (CH2OH, CH2NHR), only direct intramolecular cation-nucleophile reactions occur to give bisbenzopyrans or bisisoquinolines. Crossover products (previously obtained when the ortho substituents were OH and NH2) such as the fused benzoxepanes/fused benzoazepanes were not formed. When the ortho substituents are CO2H and vinyl groups, direct intramolecular cation-nucleophile reaction occur to give the corresponding bis--lactones and bisdihydronaphthalene, respectively. An unusual doubly-bridged, dibenzofused cyclononane derivative is also obtained in the oxidation of the ortho-vinyl-substituted stilbene. When the ortho substituents are non-nucleophilic groups such as OMe, OAc, CN, NO2, CF3, or CO2Me, the products are the tetraaryltetrahydrofurans and dehydrotetralin derivatives. In the case of an ortho-amide substituent, the major products are the tetraaryltetrahydrofurans, accompanied by a minor product incorporating an isocoumarin moiety. When the ortho substituent is a formyl group, the products include fused indanylnaphthalenes, indanylbenzopyran aldehydes, and indenyl benzaldehyde. Where an additional 3-methoxy substituent is present, additional products are formed as a result of competing aromatic substitution/Friedel Crafts reactions. Mechanistic rationalization for the formation of the various products is presented and discussed.
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| first_indexed | 2025-11-14T14:02:41Z |
| format | Thesis |
| id | um-12700 |
| institution | University Malaya |
| institution_category | Local University |
| last_indexed | 2025-11-14T14:02:41Z |
| publishDate | 2019 |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | um-127002021-12-14T19:28:26Z Reactivity of anodically-generated methoxystilbene cation radicals: The effect of ortho’-substitution / Chong Kam Weng Chong , Kam Weng Q Science (General) QD Chemistry A systematic study was undertaken to determine the influence of ortho-substituted nucleophilic (OH, NH2, CH2OH, CH2NHR, CO2H, CH=CH2) and non-nucleophilic (OMe, OAc, CN, NO2, CF3, CO2Me, CONH2, CHO) groups on the reactivity of anodically generated 4-methoxy- and 3,4-dimethoxystilbene cation radicals. The results showed that when ortho-substituted nucleophilic groups such as OH or NHR are directly attached to the aromatic ring, both direct and crossover intramolecular cation-nucleophile reactions occur to give bisbenzofurans/bisindoles or fused bisbenzopyrans/bisquinolines, respectively. When the ortho'-substituted side chains have been extended to include an intervening CH2 group (CH2OH, CH2NHR), only direct intramolecular cation-nucleophile reactions occur to give bisbenzopyrans or bisisoquinolines. Crossover products (previously obtained when the ortho substituents were OH and NH2) such as the fused benzoxepanes/fused benzoazepanes were not formed. When the ortho substituents are CO2H and vinyl groups, direct intramolecular cation-nucleophile reaction occur to give the corresponding bis--lactones and bisdihydronaphthalene, respectively. An unusual doubly-bridged, dibenzofused cyclononane derivative is also obtained in the oxidation of the ortho-vinyl-substituted stilbene. When the ortho substituents are non-nucleophilic groups such as OMe, OAc, CN, NO2, CF3, or CO2Me, the products are the tetraaryltetrahydrofurans and dehydrotetralin derivatives. In the case of an ortho-amide substituent, the major products are the tetraaryltetrahydrofurans, accompanied by a minor product incorporating an isocoumarin moiety. When the ortho substituent is a formyl group, the products include fused indanylnaphthalenes, indanylbenzopyran aldehydes, and indenyl benzaldehyde. Where an additional 3-methoxy substituent is present, additional products are formed as a result of competing aromatic substitution/Friedel Crafts reactions. Mechanistic rationalization for the formation of the various products is presented and discussed. 2019-05 Thesis NonPeerReviewed application/pdf http://studentsrepo.um.edu.my/12700/1/Chong_Kam_Weng.pdf application/pdf http://studentsrepo.um.edu.my/12700/2/Chong_Kam_Weng.pdf Chong , Kam Weng (2019) Reactivity of anodically-generated methoxystilbene cation radicals: The effect of ortho’-substitution / Chong Kam Weng. PhD thesis, Universiti Malaya. http://studentsrepo.um.edu.my/12700/ |
| spellingShingle | Q Science (General) QD Chemistry Chong , Kam Weng Reactivity of anodically-generated methoxystilbene cation radicals: The effect of ortho’-substitution / Chong Kam Weng |
| title | Reactivity of anodically-generated methoxystilbene cation radicals: The effect of ortho’-substitution / Chong Kam Weng |
| title_full | Reactivity of anodically-generated methoxystilbene cation radicals: The effect of ortho’-substitution / Chong Kam Weng |
| title_fullStr | Reactivity of anodically-generated methoxystilbene cation radicals: The effect of ortho’-substitution / Chong Kam Weng |
| title_full_unstemmed | Reactivity of anodically-generated methoxystilbene cation radicals: The effect of ortho’-substitution / Chong Kam Weng |
| title_short | Reactivity of anodically-generated methoxystilbene cation radicals: The effect of ortho’-substitution / Chong Kam Weng |
| title_sort | reactivity of anodically-generated methoxystilbene cation radicals: the effect of ortho’-substitution / chong kam weng |
| topic | Q Science (General) QD Chemistry |
| url | http://studentsrepo.um.edu.my/12700/ http://studentsrepo.um.edu.my/12700/1/Chong_Kam_Weng.pdf http://studentsrepo.um.edu.my/12700/2/Chong_Kam_Weng.pdf |