Figure 3 High-resolution ESI-MS/MS of [M –OTf]+: (a ) 9 , theinset showed an expanded view of [PhO]+ atm /z 93, (b ) 10 , (c ) 11and (d ) 12 .
To our surprise, the fragment ion [o -NO-C6H4I]+•at m /z 233 appeared in the ESI-MS/MS of [C6H5-I+-(o -NO2-C6H4)] at m/z 326 from salt 9 . Meanwhile, this same fragment ion [o -NO-C6H4I]+•at m /z 233 was also observed in the ESI-MS/MS of [10 –OTf]+ and [11 –OTf]+ (Figure 3 ). The structural assignments for fragment ions were supported by accurate mass measurements (in Table S1 and S2 ). The fragment ion [o -NO-Ar2I]+• was proposed to be the counterpart product ion of gas-phase O-atom transfer reaction from nitro to Ar1 due to the charge transfer between the neutral [o -NO-Ar2I] with [Ar1O]+. All these result supposed that the O atom in the [Ar1O]+ originated from the nitro group of Ar2 to Ar1. Consequently, the fragment ions [t Bu-C6H4O]+at m/z 149 and [o -NO-C6H4I]+•at m/z 233 in the MS/MS of [4 –OTf]+ at m/z 382 (Figure 1d and Scheme 3 ) could be attributed to the gas-phase O-atom transfer reaction from the nitro group in Ar2 to Ar1.
Scheme 5 Proposed rearrangement patterns of [M –OTf]+ of salts9 ~11 .