Ethenyl iodonium triflate

Other similar approaches have used alkenylsilanes and PhI0/Et30+ BF4 and also alkenylstannanes and PhI+CN TfO [123,124]. The reactions proceed also stereoselectively. The parent ethenyl(phenyl)iodonium triflate as well as several trisubstituted alkenyl members were obtained in this way. In an analogous manner E-alkenylzirconium compounds upon reaction with (diacetoxyiodo)ben-zene afforded -alkenyl(phenyl)iodonium salts stereoselectively [125]. 

A similar approach to aryl- and heteroaryl(phenyl)iodonium triflates 285 involves the ligand-transfer reaction between vinyliodonium salt 284 with aryllithiums (Scheme 2.83) [405]. Likewise, the reaction of ( )-[(3-(trifluoromethanesulfonyloxy)ethenyl](aryl)iodonium triflates 286 with aryllithiums or alkynyllithiums can be used for a selective preparation of the respective diaryl- or alkynyl(aryl)iodonium triflates in high yields [406]. 

Instead of silyl-, stannylalkenes are also suitable precursors [4] cyano phenyliodonium triflate (Section 9.1.4) was here the reagent of choice. This variation enabled the preparation of the parent ethenyl and several trisubstituted alkenyl phenyliodonium triflates [5], More elaborate members were obtained through additions to the triple bond of alkynyl iodonium salts, notably Diels-Alder adducts. 

The reactions of vinyl(tri-n-butyl)stannanes with the appropriate [cyano(sulfonyloxy)-iodo]benzenes in dichloromethane constitute a facile stereoselective approach to / ,/ -disubstituted vinyl(phenyl)iodonium tosylates and triflates (equation 168)130,131. Although this method has not yet been used for the preparation of a,/ -disubstituted and a,/ ,/ -trisub-stituted analogs, it has been applied to the synthesis of ethenyl(phenyl)iodonium triflate131. The efficiency of this approach may be contrasted with the early work on chlorostannanes and chloroiodanes. 

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