Iodonium special

In contrast to the previous method (equation 70), reaction 72 made possible the preparation of iodonium triflates from functionalized acetylenes bearing an electron-withdrawing group such as tosyl, cyano, or carbonyl [138]. Of special interest is the application of this method to the synthesis of the bisiodonium acetylenic salt [139, 140] (equation 73). 

Nurnberger T, Brunner F, Kemmerling BT, Piater L (2004) Innate immunity in plants and animals striking similarities and obvious differences. Immunol Rev 198 249-266 O Donnell VB, Tew DG, Jones OTG, England PJ. (1993) Studies on the inhibitory mechanism of iodonium compounds with special reference to neutrophil NADPH oxidase. Biochem J 290 41 49... 

A special method was needed for the synthesis of bis(pentafluorophenyl)-iodonium salts this was achieved either by reaction of pentafluoroiodobenzene with C6F5Xe+ TfO- or, more conveniently, from pentafluorobenzene and I(OOC-CF3)3 in strongly acidic conditions [101]. 

Special iodonium salts. A range of o-trimethylsilyl-phenyliodonioarenes [111] and heteroarenes [112] as well as some similar Wc-compounds coming from norbornadiene [113] and o-carborane [114] have been obtained from the corresponding bis trimethylsilyl precursors upon reaction with one equivalent of (diacetoxyiodo)benzene. These compounds are useful for their facile in situ conversion into benzyne-type intermediates for benzyne itself the whole procedure is available in Organic Syntheses [115]. A recent improvement involved the synthesis of a new benzyne precursor illustrated in Scheme 38 [116]. 

Some phenyliodonium salts not belonging to the above types are of special interest because they have been used as reagents, e.g. PhI+CN TfO" [135]. Another interesting iodonium salt not yet fully explored is the a-phenyliodonio-diazo compound which has been obtained from ethyl diazoacetate and (diacetoxyio-do)benzene in presence of Me3SiOTf (Scheme 49) [147]. 

In several instances BTI has been used for the preparation of other hypervalent iodine compounds, such as iodonium salts and zwitterions. Of special interest is its reaction with hard nucleophiles which attack the carbonyl carbon rather than iodine, with eventual formation of a weso-compound [61] ... 

Silyl enol ethers are quite reactive towards IOB-boron trifluoride (or tetrafluoroboric acid) and can be considered as valuable starting materials for several reactions of synthetic importance. Of special interest is their use for carbon-carbon bond formation 1,4-diketones and unsaturated ketones are the products of such reactions further, they can be transformed to oc-hydroxy, methoxy or trifyloxy ketones. With tetrafluoroboric acid IOB forms a yellow solution containing the highly electrophilic Phi+ OH BF4 , stable up to 0°C. This species reacts readily with silyl ethers of several ketones, notably acetophenones, at —78°C, forming an unstable iodonium ion (ArCOCH2I+ Ph) which with another silyl ether affords 1,4-diketones. 

Of special importance was the synthesis of bicyclic tosylenamides in tandem reactions of appropriate tosylamide-containing alkynyl iodonium salts [71] ... 

Cationic polymerizations proceed as chain reactions involving initiation and propagation. In most cases, there is no termination by neutralization, and the growing chains are terminated by nucleophilic impurities. Cationic chain reactions are photoinitiated by special initiators (Table 3.10) which date back to the pioneering studies of Crivello on sulfonium and iodonium salts containing non-nucleophilic anions such as and AsFs ... 

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