Study of the Gas-Phase Intramolecular Aryltrifluoromethylation of Phenyl(Trifluoromethyl)Iodonium by ESI-MS/MS

The gas-phase reactions of the reactive lambda (3)-phenyl(trifluoromethyl)iodonium (PhI+(III)CF3, 1 at m/z 273) to the radical cation of iodobenzene (PhIaEuro cent+, 2 at m/z 204) via the loss of center dot CF3 and the radical cation of trifluoromethylbenzene (PhCF3 (aEuro cent+), 3 at m/z 146) via the loss of center dot I, were studied by electrospray ionization tandem mass spectrometry (ESI-MS/MS). Interestingly, the gas-phase intramolecular coupling reaction of CF3 with phenyl via the CF3 migration process of 1 at m/z 273 from iodine to the phenyl to give 3 at m/z 146 could only occur according to an intramolecular aromatic substitution mechanism. Density functional theory (DFT) calculations showed that the gas-phase intramolecular aryltrifluoromethylation of 1 at m/z 273 to 3 at m/z 146 occurred via a Meisenheimer complex intermediate (MC), where the triplevalent I center of 1 was reduced to monovalent I. Most importantly, the structure of 3 at m/z 146 derived from 1 at m/z 273 in ESI-MS/MS process was confirmed by comparison of its MS/MS with that of an authentic PhCF3 (aEuro cent+) at m/z 146 acquired from the electron ionization (EI)-MS/MS analysis of PhCF3. Thus, our studies revealed the intrinsic reactivity tendencies of lambda(3)-phenyl(trifluoromethyl)iodonium under solvent-free conditions.