Transition-metal-free approaches towards synthesis of nitrogen-containing molecules
Nitrogen-containing molecules are omnipresent in biologically active natural products, pharmaceutical drugs and functional materials. To date, numerous transition-metal-catalyzed reactions have been investigated and applied towards synthesis of nitrogen-containing molecules. On the other hand, devel...
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| Format: | Thesis |
| Language: | English |
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2015
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| Online Access: | http://hdl.handle.net/10356/65742 |
| _version_ | 1826126867063635968 |
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| author | Zhang, Feng-Lian |
| author2 | Chiba Shunsuke |
| author_facet | Chiba Shunsuke Zhang, Feng-Lian |
| author_sort | Zhang, Feng-Lian |
| collection | NTU |
| description | Nitrogen-containing molecules are omnipresent in biologically active natural products, pharmaceutical drugs and functional materials. To date, numerous transition-metal-catalyzed reactions have been investigated and applied towards synthesis of nitrogen-containing molecules. On the other hand, development of efficient supply for valuable nitrogen-containing molecules by transition-metal-free approaches is becoming more and more desirable considering the recent environmental sustainability issues as well as strict international standards about the level of transition-metal contamination in the drug ingredients. The author has developed new synthetic methods of azaheterocycles and amides operated under transition-metal-free manners during the PhD study and the detailed results will be described in this thesis. Part I of this thesis describes molecular oxygen-induced radical transformations for synthesis of azaheterocycles. Molecular oxygen (O2), as a triplet diradical in its ground state, has the ability to trigger cleavage of X-H (X = C, O) bonds through single-electron-oxidation or hydrogen abstraction pathways. It was found that
amidoximes bearing relatively low BDEs of O-H bonds (80-90 kcal/mol) could generate iminoxyl radicals by O2-triggered O-H bond cleavage. The resulting iminoxyl radical underwent 1,5-H radical shift to form the corresponding C-radical, that was further transformed to 4,5-dihydro-1,2,4-oxadiazole. This 4,5-dihydro-1,2,4-oxadiazole was further oxidized to 1,2,4-oxadiazole or converted into quinazolinone through oxidative skeletal rearrangement (Scheme 1). These results are summarized in Chapter 2. |
| first_indexed | 2024-10-01T06:59:23Z |
| format | Thesis |
| id | ntu-10356/65742 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T06:59:23Z |
| publishDate | 2015 |
| record_format | dspace |
| spelling | ntu-10356/657422023-02-28T23:52:24Z Transition-metal-free approaches towards synthesis of nitrogen-containing molecules Zhang, Feng-Lian Chiba Shunsuke School of Physical and Mathematical Sciences DRNTU::Science::Chemistry::Organic chemistry::Heterocyclic compounds DRNTU::Science::Chemistry::Organic chemistry::Organic synthesis Nitrogen-containing molecules are omnipresent in biologically active natural products, pharmaceutical drugs and functional materials. To date, numerous transition-metal-catalyzed reactions have been investigated and applied towards synthesis of nitrogen-containing molecules. On the other hand, development of efficient supply for valuable nitrogen-containing molecules by transition-metal-free approaches is becoming more and more desirable considering the recent environmental sustainability issues as well as strict international standards about the level of transition-metal contamination in the drug ingredients. The author has developed new synthetic methods of azaheterocycles and amides operated under transition-metal-free manners during the PhD study and the detailed results will be described in this thesis. Part I of this thesis describes molecular oxygen-induced radical transformations for synthesis of azaheterocycles. Molecular oxygen (O2), as a triplet diradical in its ground state, has the ability to trigger cleavage of X-H (X = C, O) bonds through single-electron-oxidation or hydrogen abstraction pathways. It was found that amidoximes bearing relatively low BDEs of O-H bonds (80-90 kcal/mol) could generate iminoxyl radicals by O2-triggered O-H bond cleavage. The resulting iminoxyl radical underwent 1,5-H radical shift to form the corresponding C-radical, that was further transformed to 4,5-dihydro-1,2,4-oxadiazole. This 4,5-dihydro-1,2,4-oxadiazole was further oxidized to 1,2,4-oxadiazole or converted into quinazolinone through oxidative skeletal rearrangement (Scheme 1). These results are summarized in Chapter 2. Doctor of Philosophy (SPMS) 2015-12-11T02:38:51Z 2015-12-11T02:38:51Z 2015 2015 Thesis Zhang, F.-L. (2015). Transition-metal-free approaches towards synthesis of nitrogen-containing molecules. Doctoral thesis, Nanyang Technological University, Singapore. http://hdl.handle.net/10356/65742 en 216 p. application/pdf |
| spellingShingle | DRNTU::Science::Chemistry::Organic chemistry::Heterocyclic compounds DRNTU::Science::Chemistry::Organic chemistry::Organic synthesis Zhang, Feng-Lian Transition-metal-free approaches towards synthesis of nitrogen-containing molecules |
| title | Transition-metal-free approaches towards synthesis of nitrogen-containing molecules |
| title_full | Transition-metal-free approaches towards synthesis of nitrogen-containing molecules |
| title_fullStr | Transition-metal-free approaches towards synthesis of nitrogen-containing molecules |
| title_full_unstemmed | Transition-metal-free approaches towards synthesis of nitrogen-containing molecules |
| title_short | Transition-metal-free approaches towards synthesis of nitrogen-containing molecules |
| title_sort | transition metal free approaches towards synthesis of nitrogen containing molecules |
| topic | DRNTU::Science::Chemistry::Organic chemistry::Heterocyclic compounds DRNTU::Science::Chemistry::Organic chemistry::Organic synthesis |
| url | http://hdl.handle.net/10356/65742 |
| work_keys_str_mv | AT zhangfenglian transitionmetalfreeapproachestowardssynthesisofnitrogencontainingmolecules |