Investigation of Sulfur(VI) Chemistry

This thesis focuses closely on the latest advancements in the synthesis of sulfur(VI) analogues, namely sulfonimidates and sulfoximines. A detailed analysis of their applications and syntheses is reported into two sections: synthesis of racemic sulfoximines from acyclic sulfonimidates, and secondly, the synthesis of enantioenriched NH-sulfoximines from cyclic sulfonimidates. The route towards the synthesis of racemic sulfoximine products starting from sulfinamides (sulfur(IV) species) that were converted into sulfonimidates through a hypervalent iodine mediated oxidative alkoxylation reaction and explored in detail to allow modification of the core structure. Subjecting the acyclic sulfonimidates to Grignard reaction conditions allowed a general method for C-S bond formation to be explored and adding a third point of diversity to the sulfoximine products. The second part of the results and discussion closely follows the synthesis of cyclic sulfonimidates and their subsequent conversion into sulfoximine products. Oxidative chlorination of sulfinamides followed by cyclisation allows access to cyclic sulfonimidates. Structural diversity was investigated further through Grignard addition to these cyclic sulfonimidate templates. Furthermore, the stereochemical outcome of all steps towards sulfoximines was carefully monitored by X-ray crystallography. Pleasingly, NH-sulfoximines were isolated using basic conditions under an oxygen atmosphere to cleave the phenylethanol moiety with no loss of stereochemical information at sulfur during this transformation giving free NH-sulfoximines with excellent enantiomeric excess