Diaryliodonium salts are versatile reagents that are utilised for several transformations in organic chemistry. They are mainly used in transition metal-free arylations of C-, N-, O- as well as S-nucleophiles and show a high efficiency in transition metal catalysed reactions due to their high activity towards oxidative addition. Furthermore, diaryliodonium salts are considered as low toxic reagents that can be synthesised in one-pot procedures.

In Chapter 1 the term hypervalent iodine is introduced along with structure, reactivity and synthesis of diaryliodonium salts. To understand later research topics nucleophilic aromatic substitution, including electronic and structural factors that influence reactivity and selectivity are described. Furthermore, sustainability in organic chemistry is discussed through selected examples along with discussions about the principles of green chemistry.

In Chapter 2 we present a strategy for the synthesis of novel functionalised diaryliodonium salts that would not be possible to synthesise under the acidic and oxidative state-of-the-art conditions. The incorporation of these functionalities is done via S_NAr utilising amines, phenols and anilines as nucleophiles, enabling the synthesis of more than 50 novel functionalised iodonium salts. In Chapter 3, reactivity studies give insight into competing functionalities in these reagents as well as downstream diversifications to show the applicability of the novel products.

Diaryliodonium salts are typically synthesised in non-sustainable solvents such as dichloromethane. In Chapter 4 we show that it is possible to form these reagents in the more sustainable solvent ethyl acetate. A plethora of salts are presented with useful ligands for synthesis using these compounds. To prove the robustness of the method three large-scale reactions are performed and their sustainability assessed by E-factors.

Finally, in Chapter 5 we present a one-pot functionalisation of arenes and iodoarenes by combining our method for the synthesis of iodonium salts in ethyl acetate with a consecutive arylation of sodium thiocyanate, potassium ethyl xanthate and sodium nitrite, avoiding the isolation of an iodine(III) intermediate.