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.

邻位取代官能化炔烃o-RC≡C(C₆H₄)NO₂（R = H或烷基）可与两分子氢化铱（iridium hydrides）发生形式插入反应，过程中可观测到硝基（nitro group）向该炔烃的碳碳三键发生氧转移（O-transfer）。当底物为R=H的末端炔烃（terminal alkyne）时，可分离得到铱(III)亚硝酰配合物（iridium(III) nitroso complexes）。当底物为R=甲基（Me）或正丙基（nPr）的内炔烃（internal alkynes）时，经区域选择性（regiochemistry）不同的氧转移过程，可得到氢化铱苯并异噁唑（anthranil）配合物。本文提出了上述转化的反应机理，其中包含了此前未见报道的、从硝基向RC≡C键发生氧转移的关键步骤。