New methodology in iodonium salt synthesis. Reactions of [hydroxy(tosyloxy)iodo]arenes with aryltrimethylsilanes

Diaryliodonium Salts: A Journey from Obscurity to Fame

“…The reaction of hydroxy(tosyloxy)iodobenzene (PhI(OH)OTs, Kosers reagent) with arylsilanes under neutral conditions occurred at the ipso-position regardless of substituents (Scheme 4 b). [19] Substituted versions of Kosers reagent could also be employed, delivering both symmetric and unsymmetric salts in moderate yields. Electron-rich arenes, such as thiophene, react with ArI(OH)OTs without need for the trimethylsilyl (TMS) activating group.…”

ipso-Fluorination of aryltrimethylsilanes using xenon difluoride

“…It is known that hypervalent iodine reagents react with aryltrimethylsilanes 1 to give diaryliodonium salts. 3 We anticipated that, in a similar manner, xenon difluoride would give the intermediate cation 2, which can be stabilized by both the b-effect of the trimethylsilyl substituent and interaction with the non-bonding molecular orbital associated with the hypervalent xenon bonds. Subsequent elimination of fluorotrimethylsilane (Me 3 SiF) can lead to an aryl xenon derivative 3, which undergoes ligand coupling to form the desired aryl fluoride 4 (Scheme 1).…”

Xenon difluoride in the organic laboratory: a tale of substrates, solvents and vessels

“…We were aware that a hypervalent derivative of iodine, [hydroxy-(tosyloxy)iodo]benzene 9 (Koser's reagent), reacts with aryltrimethylsilanes 10 to give diaryliodonium tosylates 11 (Equation 1). 15 On the assumption that hypervalent iodine and hypervalent xenon might have properties in common, we wondered if XeF 2 might similarly react with aryltrimethylsilanes 10 to give arylxenon fluorides 12 followed by ligand coupling to give aryl fluorides (Equation 2). Mechanistically this seemed reasonable on the assumption that electrophilic addition of XeF 2 to aryltrimethylsilanes might lead to the intermediate cations 13 in which the  system of the cation is stabilised by the NBMO of the hypervalent xenon and by the  effect of the trimethylsilyl substituent.…”