Intramolecular Oxygen Transfer from Nitro Groups to C⋮C Bonds Mediated by Iridium Hydrides

The functionalized alkynes o-RC⋮C(C6H4)NO2 (R = H or alkyl) formally insert into two
iridium hydrides, during which O-transfer of the nitro group into the C⋮C bond of o-RC⋮C(C6H4)NO2 is observed. For the terminal alkyne with R = H, iridium(III) nitroso complexes
were isolated. For internal alkynes with R = Me or nPr, iridium hydride anthranil complexes
were obtained as a result of O-transfer with a different regiochemistry. Mechanisms for
these transformations, including a previously unknown O-transfer step from the nitro to
the RC⋮C bond, are proposed.