Bisiodonium triflates

The synthetic potential of coupling reactions between vinyliodonium salts and organocuprates has not been exploited. However, some indication of their promise is provided by reported syntheses of bicyclic enediynes in the norbornadiene and 7-oxanor-bornadiene series from the appropriate bisiodonium triflates and lithium dialkynyl-cuprates (equation 221)148. 

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). 

The propensity of the thiocyanate ion for alkynylation with alkynyliodonium ions has also been demonstrated with a series of bis(phenyliodonium)diyne triflates (equations 61 and 62)43. The efficient production of diynediyl dithiocyanates in these reactions may be contrasted with the favored formation of mono- and bis-cyclopentenyl sulfones from bisiodonium diyne salts and sodium/ -toluenesulfinate (see equation 57)86. 

The reactions of various bisiodonium diyne triflates with two equivalents of triph-enylphosphine in dichloromethane similarly result in alkynylation of the nucleophile and afford good yields of bisphosphonium diyne triflates (equations 74 and 75)42. 

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