Figure 1 High-resolution ESI-MS/MS of [M –OTf]+: (a ) 1 , (b ) 2 , (c ) 3 and (d )4 .
Scheme 3 Proposed fragmentation patterns of [M –OTf]+: (a ) 1 , (b ) 2 , (c ) 3 and (d )4 .
When we examined diaryliodonium salt 4 with introduction of a nitro group into Ar2, We not only observed fragment ions consistent with the processes outlined in Scheme 3 but also identified novel types of fragment ions: [t Bu-C6H4O]+at m/z 149 and [p -NO-C6H4I]+•at m/z 233 in the ESI-MS/MS of [(p -t Bu-C6H4)-I+-(p -NO2-C6H4)] at m/z 382 (Figure 1d and Scheme 3 ). These findings strongly suggested the involvement of a gas-phase O-atom transfer reaction from the nitro group to the aryl moiety in the ESI-MS/MS of [(p -t Bu-C6H4)-I+-(p -NO2-C6H4)]. It could be attributed to the presence of a nitro group in Ar2 of the diaryliodonium cations.