Mild Oxidation of C?C Bonds of Benzoiridacycles

We describe herein the formation of two metallacyclic derivatives, 4b and 5b, which contain a coordinated ketone functionality (from an ?-keto ester metallacyclic substituent). An iridafuran, 6, that results from the reaction of TpMe2Ir(Ph)2(N2) (TpMe2 = hydrotris(3,5-dimethylpyrazolyl)borate) with di-tert-butyl acetylenedicarboxylate (DTAD) and oxygen is also reported. Our results reveal that the reactions proceed through iridacycle intermediates (detected by NMR) resulting formally from the coupling of one (in the case of 6) or two (for 4b and 5b) molecules of DTAD, with the metal unit TpMe2Ir(C6H4) derived from the iridium precursor. These intermediates experience very mild and selective oxidation by air to incorporate one (4b and 5b) or three (6) oxygen atoms in the final oxidation products.