Synthesis of distally substituted thioether resorcinarene ligands

Bhana, Ashlyn (2017-12)

Thesis (Msc)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: In this thesis it is reported the attempts to synthesise a series of distal thioether functionalised resorcinarene ligands. Chapter 1 provides an overview in order to familiarize the reader about the history and synthesis of resorcinarenes as well as methods pertaining to the functionalization of resorcinarenes. In particular the synthesis of resorcinarenes for use as ligands in metal complexes as well as some examples of such resorcinarene-metal complexes are provided within this chapter. It is reported that resorcinarenes are mostly exploited within the application of host-guest complexes, but that only a few examples of resorcinarenes that are used as ligands for catalysis exist and are reported within the literature. Chapter 2 discusses the synthesis of parent resorcinarenes and the attempted synthesis of distal thioether resorcinarene ligands via the ortholithiation approach, using disulphides and sulfenyl chlorides as electrophiles. The ortholithiation procedure was compatible when using dimethyl disulphide as the electrophile; however the use of di-tert-butyl disulphide and benzenesulfenyl chloride as electrophiles returned negative results. Benzenesulfenyl chloride was successful when used as an electrophile within the ortholithiation procedure of the model system, 1,3-dimethoxybenzene, whereas di-tert-butyl disulphide was unsuccessful in this regard. Chapter 3 discusses the investigation into the attempted synthesis of a series of distal thioether resorcinarene ligands. This was attempted via transition metal catalysis as resorcinarenes can easily be functionalized with bromine which can be compared to aryl bromides which are commonly used as precursors in such coupling reactions. The literature suggested that copper and palladium would be good candidates to perform thioetherfication, the coupling of thiols to aryl bromides, on the resorcinarene. Copper mediated thioetherfication reactions were tested on the pre-functionalized model system, 2-bromo-1,3-dimethoxybenzene, and showed low conversion of starting materials. Palladium mediated thioetherfication reactions were also tested on the same model system, performed with the reportedly highly active [Pd(IPr*OMe)(cin.)(Cl)] catalytic species, and returned near quantitative yields of the coupled product. When the same catalytic species was tested on a distal dibromo resorcinarene precursor, however only starting material was isolated from the reaction. Chapter 4, Conclusions and Future Work, and Addendum A discusses work that was only preliminary and not thoroughly investigated due to time constraints. Future work towards the attempted synthesis of distal thioether resorcinarene ligands via catalysis, the use of sulphur nucleophiles or using different types of sulphur-derived electrophiles within the ortholithiation approach are also discussed within these two chapters.

AFRIKAANSE OPSOMMING: In hierdie tesis word die pogings van die sintese van ‟n reeks van distaal tio-eter gefunksioneerde resorsinareenligande gerapporteer. Hoofstuk 1 bied ‟n oorsig om die leser bekend te stel aan die geskiedenis en sintese van resorsinarene. In besonder word die sintese van resorsinarene vir die gebruik as ligande in metaalkomplekse bespreek sowel voorbeelde van resorsinareen-metaalkomplekse word verskaf in die hoofstuk. Dit word gerapporteer in die literatuur dat resorsinarene word meestal gebruik in die toepassing van gas-gasheer komplekse. Daar onstaan net ‟n klein hoeveelheid resorsinarene wat word gebruik as ligande vir katalise. Hoofstuk 2 bespreek die sintese van resorsinarene en die poging tot die sintese van distaal tio-eter resorsinareenligande deur die orto-litiëringbenadering wanneer di-sulfiede en sulfenielchloriede word gebruik as elektrofiele. Die orto-litiëring prosedure was versoenbaar wanneer dimetiel disulfied gebruik word as die elektrofiel; alhoewel die gebruik van di-tert-butiel disulfied en benseensulfenielchloried as elektrofiele negatiewe resultate opgelewer het. Benseensulfenielchloried was suksesvol wanneer dit gebruik was in die orto-litiëring prosedure van ‟n model sisteem, 1,3-dimethoksybenseen, terwyl di-tert-butiel disulfied was onsuksesvol in die verband. Hoofstuk 3 bespreek die ondersoek in ‟n poging tot die sintese van distaal tio-eter resorsinareenligande deur oorgangsmetaal katalise as gevolg van die feit dat resorsinarene kan maklik gefunksionaliseer word met broom wat kan vergelyk word met arielbromied wat in die algemeen gebruik as voorlopers in sulke koppelingsreaksies. Die literatuur het aangedui dat koper en palladium goeie kandidate sou wees om tio-eterfikasie uit te voer, die koppeling van tiole aan arielbromiede, op die resorsinareen. Die bemiddeling van koper tio-eterfikasie was getoets op ‟n arielbromied model sisteem, 2-broom-1,3-dimethoksybenseen, en het laag omskakeling van uitgangsmateriaal getoon. Die bemiddeling van palladium tio-eterfikasie reaksies was ook getoets op dieselfde model sisteem, uitgevoer deur die gerapporteerde hoogs aktiewe [Pd(IPr*OMe)(cin.)(Cl)] katalitiese spesie, en het ‟n baie na aan kwantitatiewe opbrengs van die gekoppelde produk opgelewer. Wanneer dieselfde katalitiese spesie getoets was op die distaal dibroom resorsinareen voorloper, het die reaksie net uitgangsmateriaal opgelewer. Hoofstuk 4 (Gevolgtrekkings en Toekomstige Werk) en Aanhangsel A bespreek voorlopige werk wat nie deeglik ondersoek en nagevors was nie as gevolg van beperkings in terme van tyd. Toekomstige werk teenoor die pogings tot die sintese van distaal tio-eter resorsinareenligande deur katalise, die gebruik van swaelnukleofiele of die gebruik van verskillende tipe swael-afgeleide elektrofiele in die orto-litiëringbenadering word ok bespreek in die twee hoofstukke.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/102735
This item appears in the following collections: