Synthesis of distally substituted thioether resorcinarene ligands

[摘要] 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.

[发布机构] Stellenbosch University