Vinyliodonium tetrafluoroborates

Vinyliodonium tetrafluoroborates.l These salts are obtained with retention of configuration by reaction of vinylsilanes with iodosylbenzene activated with triethyloxonium tetrafluoroborate (equation I). 

Vinyliodonium salts.3 Reaction of vinylsilanes (2) with iodosylbenzene catalyzed by BF3 etherate results in vinyliodonium tetrafluoroborates (3) in generally... 

The nitrite ion behaves as a nitrogen nucleophile with vinyliodonium ions. Thus, admixture of the vinyliodonium tetrafluoroborates shown in equations 188 and 189 with sodium nitrite results in the production of nitroalkenes119,125,126. Cupric sulfate is apparently necessary for the success of the latter reaction, although its role has not been clarified. The (cyclohexenyl)iodonium salt also reacts with sodium thiophenoxide to give the corresponding vinyl phenyl sulfide125,126. 

The production of the (Z)-haloalkenes is thought to proceed via initial exchange of the tetrafluoroborate and halide ions and collapse of the resulting vinyliodonium halides by the addition-elimination (Ad-E) mechanism (equations 203 and 204)84. As with Ad-E reactions of moderately activated vinyl halides (X = Cl, Br), which typically occur with configurational retention (> 95%)143 145, the intermediate carbanions apparently prefer a least motion rotation of 60° prior to the expulsion of iodobenzene. It has been demonstrated by an NMR study that anion exchange between (Z)-(2)-phenylsulfonyl-l-decenyl)-phenyliodonium tetrafluoroborate and tetrabutylammonium chloride occurs instantaneously in deuteriochloroform84. Furthermore, when authentic halide salts of the... 

Anion exchange between (E)-1 -decenyl(phenyl)iodonium tetrafluoroborate and TB AC1 occurs instantaneously in CDC13 at room temperature, while addition of the authentic chloride salt to dichloromethane (rt) affords a 45 55 mixture of (Z)-l-chlorodecene and 1-decyne146. Thus, the reactions shown in equations 206-208 are thought to involve the initial formation of vinyliodonium halides which then give rise to the observed products. 

In an effort to demonstrate the synthetic utility of vinyliodonium salts, small-scale reactions of (4-rm-butyl-1 -cyclohexenyl)phenyliodonium tetrafluoroborate (62) with various nucleophilic species, especially copper(I) reagents, have been conducted125,126. The copper(I)-assisted reactions include the conversions of 62 to 1-cyano-, 1-halo-, 1-alkyl- and 1-phenyl-4-ter r-butylcyclohexenes (equation 215). The alkylation and phenylation of the cyclohexenyl ligand in 62 with lithium diorganocuprates is noteworthy, since the treatment of 62 with H-butyllithium leads to fragmentation of the iodonium ion and affords only a 0.2% yield of 1 -w-butyl-4-terr-butylcyclohexene (equation 216)126. 

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