Alkenyl iodonium salts, preparation alkynes

Simple and phenylated alkynes were prepared from alkenyl iodonium salts and lithium organocuprates. 

There are two approaches for the preparation of alkenyl(phenyl)iodonium salts reaction of an activated alkene with an iodine(III) species and addition to a triple bond, either of simple alkynes or of alkynyl(phenyl)iodonium salts. 

Vinyliodonium ions, 35 and 36, are hypervalent iodine species in which one or two alkenyl ligands are bound to a positively charged iodine(III) atom. Although they are reactive with nucleophilic reagents, they are less labile than alkynyliodonium ions, and stable halide salts of vinyliodonium ions can be prepared. The first vinyliodonium compounds [i.e. (a, / -dichlorovinyl)iodonium salts] were synthesized by the treatment of silver acetylide-silver chloride complexes with (dichloroiodo)arenes or l-(dichloroiodo)-2-chloroethene in the presence of water (equation 152). The early work was summarized by Willgerodt in 1914115. This is, of course, a limited and rather impractical synthetic method, and some time elapsed before the chemistry of vinyliodonium salts was developed. Contemporary synthetic approaches to vinyliodonium compounds include the treatment of (1) vinylsilanes and vinylstannanes with 23-iodanes, (2) terminal alkynes with x3-iodanes, (3) alkynyliodonium salts with nucleophilic reagents and (4) alkynyliodonium salts with dienes. 

Several types of functionalized alkenyl(aryl)iodonium salts have been prepared by the addition of hyperva-lent iodine reagents to alkynes. Reactions of terminal alkynes with iodosylbenzene and triflic acid proceed as a highly stereoselective anti-addition to afford ( )-(P-trifluoromethanesulfonyloxyaIkenyl)phenyliodonium triflates 310 in high yield (Scheme 2.90) [446-448], Similar products were obtained Ifom the reactions of internal alkynes and parent acetylene [447],... 

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