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Oxazoline directed lithiation of Calix[4]arene and Ferrocene
Thesis (PhD)--Stellenbosch University, 2011.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2011
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| _version_ | 1867614087972651008 |
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| access_status_str | Open Access |
| author | Herbert, Simon Anthony |
| author2 | Arnott, Gareth E. |
| author_browse | Arnott, Gareth E. Herbert, Simon Anthony |
| author_facet | Arnott, Gareth E. Herbert, Simon Anthony |
| author_sort | Herbert, Simon Anthony |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2011. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/17867 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:46:28.519Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2011 |
| publishDateRange | 2011 |
| publishDateSort | 2011 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/17867 Oxazoline directed lithiation of Calix[4]arene and Ferrocene Herbert, Simon Anthony Arnott, Gareth E. Stellenbosch University. Faculty of Sciences. Dept. of Chemistry and Polymer Science. Chirality Calixarenes Ferrocene Oxazoline Ortholithiation Ligand tuneable diastereoselectivity Dissertations -- Chemistry Theses -- Chemistry Chemistry and Polymer Science Thesis (PhD)--Stellenbosch University, 2011. ENGLISH ABSTRACT: The use of chiral oxazoline directed lithiation provides a highly diastereoselective (up to >99% de) route to meta functionalised inherently chiral calixarenes. This methodology can be used on both the butylated and debutylated calixarene systems and is tolerant of a wide range of different electrophillic quenches allowing access to a structurally diverse range of inherently chiral metafunctionalised calixarenes. The oxazoline directing group can be removed via hydrolysis, generating a range of functionalised calixarene carboxylic acids in high ee. We also demonstrate that the use of derivative alkyllithiums such as cyclopentyl lithium can provide significantly enhanced diastereoselectivity over the conventional organolithiums such as sec-butyl lithium, when employed in ortholithiation reactions of this nature. The differences in diastereoselectivity associated with the different alkyllithiums can be tied, in certain cases, to the steric bulkiness associated with the individual reagents. In this regard we have found that the use of the so called Tolman angle or cone angle approach allows quantification of the relative steric bulk of the alkyllithium. We also detail that the oxazoline directing group provides a hitherto unknown ability to be diastereoselectively tuned through the choice of the ligand system in the ortholithiation reaction. In this regard the development of a series of diglyme based ligands have proved to provide a highly diastereoselective means of inverting the chirality from that which the use of the conventional TMEDA ligand is able to generate (up to –92% de). The use of diglyme ligands to invert the sense of chirality is also shown to occur on the ferrocenyloxazoline system and presents an apparently general and hitherto unknown facet of asymmetric oxazoline directed ortholithiation. This diglyme induced inversion has been shown to be controlled through a secondary nitrogen coordinated mechanism that is able to operate with chiral oxazolines. AFRIKAANSE OPSOMMING: Die gebruik van chirale oksasoliengerigte litiëring verskaf ’n hoogs diastereoselektiewe (tot en met >99% do) roete om metagefunksionaliseerde, inherente chirale calixareen produkte te sintetiseer. Deur gebruik te maak van verskillende elektrofiele kan die metodologie toegepas word op beide gebutileerde en de-gebutileerde calixareen sisteme om ’n reeks uiteenlopende inherente chirale, meta-gefunksionaliseerde calixareen produkte te vorm. Die oksasolien groep kan daarna verwyder word deur hidroliese om ’n reeks gefunksionaliseerde calixareenkarboksielsure te vorm in baie hoë eo. Ons het ook gedemonstreer dat die gebruik van afgeleide alkiel-litiums, soos siklopentiel-litium, kan bydrae tot aansienlik verhoogde diastereoselektiwiteit as dit vergelyk word met meer algemene organolitiums soos sekbutiellitium, tydens ortolitiëring reaksies van hierdie natuur. Die verskille in diastereoselektiwiteit kan verbind word, in sekere gevalle, tot die steriese bonkigheid van die individuele reagense. Deur gebruik te maak van die sogenaamde Tolmanhoeke of die koniesehoek benadering is dit moontlik om die relatiewe steriese bonkighied van alkiellitiums te kwantifiseer. Daar was ook bepaal dat die oksasoliengroep die ongekende vermoë besit om die diastereoselektiwiteit van die produk te stem deur die keuse van verskillende ligand sisteme tydens die ortolitiëring reaksie. Daar was bepaal dat die chiralitiet van die produkte omgekeer kan word op ’n hoogs diastereoselektiewe manier, deur gebruik te maak van ’n reeks ontwikkelde diglymegebaseerde ligande, indien dit vergelyk word met die produkte wat deur die konvensionele TMEDA gegenereer was (tot en met –92% do). Die gebruik van diglyme ligande was ook getoets op ferroseenoksasolien sisteme en dit was bevind dat dieselfde omkering in chiraliteit ook plaasvind wat aanleiding kan gee tot 'n oënskynlik algemene en tot nou toe onbekende faset van asimmetriese oksasoliengerigte orto-litiëring. Dit is bepaal dat hierdie diglyme geïnduseerde omkering in chiraliteit beheer word deur middel van 'n sekondêre stikstofgekoördineerde meganisme, wat in staat is om saam te werk met chirale oksasoliene. Doctoral 2011-11-11T08:32:05Z 2011-12-05T13:06:24Z 2011-11-11T08:32:05Z 2011-12-05T13:06:24Z 2011-11-11T08:32:05Z 2011-12 Thesis http://hdl.handle.net/10019.1/17867 en_ZA Stellenbosch University application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Chirality Calixarenes Ferrocene Oxazoline Ortholithiation Ligand tuneable diastereoselectivity Dissertations -- Chemistry Theses -- Chemistry Chemistry and Polymer Science Herbert, Simon Anthony Oxazoline directed lithiation of Calix[4]arene and Ferrocene |
| title | Oxazoline directed lithiation of Calix[4]arene and Ferrocene |
| title_full | Oxazoline directed lithiation of Calix[4]arene and Ferrocene |
| title_fullStr | Oxazoline directed lithiation of Calix[4]arene and Ferrocene |
| title_full_unstemmed | Oxazoline directed lithiation of Calix[4]arene and Ferrocene |
| title_short | Oxazoline directed lithiation of Calix[4]arene and Ferrocene |
| title_sort | oxazoline directed lithiation of calix 4 arene and ferrocene |
| topic | Chirality Calixarenes Ferrocene Oxazoline Ortholithiation Ligand tuneable diastereoselectivity Dissertations -- Chemistry Theses -- Chemistry Chemistry and Polymer Science |
| url | http://hdl.handle.net/10019.1/17867 |
| work_keys_str_mv | AT herbertsimonanthony oxazolinedirectedlithiationofcalix4areneandferrocene |