Synthesis of substituted tetrahydron-1H-carbazol-1-one and analogs via PhI(OCOCF3)2-mediated oxidative C-C bond formation

A variety of tetrahydro-1H-carbazol-1-ones and analogs were conveniently synthesized from the reaction of the corresponding 2-(phenylamino)cyclohex-2-enone with hypervalent iodine reagent PhI(OCOCF3)2 (PIFA), through a direct intramolecular oxidative C(sp2)-C(sp2) bond formation. This approach realized the construction of the biologically important tetrahydro-1H-carbazol-1-one and tetrahydrocyclohepta[b]indol-6(5H)-one skeletons. The mechanism of the process was proposed and briefly discussed.