Hypervalent iodine compounds diaryliodonium salts

Diaryliodonium salts, with few exceptions, are stable compounds towards heat, oxygen and humidity they are mildly light-sensitive and should be stored in the dark, without refrigeration. Generally, their reactivity is less pronounced than that of other hypervalent iodine compounds. Indeed, in several of their reactions relatively drastic conditions may be necessary, especially for the least reactive heterocyclic iodonium salts. The search for optimum conditions is often desirable even for well-established reactions, by applying new findings concerning the use of specific... 

Diaryliodonium salts and other hypervalent iodine compounds in the synthesis of biaryls... 

Aqueous media are often used for reactions with hypervalent iodine compounds. A number of mild and selective methods for arylation of acetylenes by diaryliodonium salts have been published. In neat water the reaction is run at room temperature in a heterogeneous system (PdCl2(PPh3)2, Cul, K2CO3, 10 mol % BU3N) and must be assisted by amine base, which possibly additionally serves as PTC agent. ... 

The focus of this chapter is to provide an overview of the reactivity of diaryliodonium salts, discuss common synthetic routes to them, and describe the recent developments in applications of these reagents after a brief historical perspective in each section. The chemistry of hypervalent iodine compounds has been summarized in a number of books and reviews [1-3], and the topics of diaryliodonium salts [4, 5], cyclic diaryliodonium salts [6], and iodonium salts [7] have been reviewed. Literature summaries of mechanistic aspects and selected transformations with diaryliodonium salts are referenced in the appropriate sections below. 

With the development of efficient synthetic routes to diaryliodonium salts, these hypervalent iodine compounds have become easily available and interesting alternatives to other arylation reagents. Their low toxicity, high stability, and high reactivity are attractive features which enable difficult transformations without the need for excess reagents or high temperatures. This chapter has summarized recent developments in metal-free and metal-catalyzed arylations of heteroatom nucleophiles and carbon-centered nucleophiles. The boundaries of the field have moved forward considerably in the last decade, and many more applications are foreseen based on the deepened mechanistic understanding of arylations under both metal-free and metal-catalyzed conditions. 

Recent progress on the use of hypervalent iodine reagents for the construction of heteroatom-heteroatom bonds is reviewed. Reactions of aryl-A3-iodanes with heteroatom substrates derived from third-row elements and beyond are considered first, and an unusual example of heteroatom-heteroatom bond formation with diaryliodonium salts is then discussed. Finally, the use of sulfonylimino(aryl)iodanes for imidations of phosphorus, sulfur, selenium, and arsenic compounds, including enantioselective transformations (S,Se), and alternate hypervalent iodine approaches to N-sulfonylsulfilimines and N-sulfonylarsinimines are summarized. 

Notorious toxicity of heavy metal compounds can be avoided using hypervalent iodine(III) reagents [131]. Diaryliodonium salts yield biaryls in the reaction with methylmagnesium bromide in the... 

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