Synthesis Of Substituted Tetrahydron-1H-carbazol-1-one And Analogs Via PhI（OCOCF₃）₂-mediated Oxidative C-C Bond Formation

Among the structurally important nitrogen-containing heterocycles, tetrahydro-1H-carbazol-1-one and its analogs have been widely identified in many prodrugs,including anti-bacterial, anti-HIV, anti-human papillomaviruses (HPV), anti-prion,anti-tumor ones and the like. As the importance of this structure, more researcherspaid their attention on the synthesis of this skeleton and several methods have beendiscovered so far. Based on the former work on the C-C bond coupling reaction viahypervalent iodine reagents, we proposed a unique method for the synthesis oftetrahydro-1H-carbazol-1-ones and analogs in the presence of PIFA.As the starting materials,2-(substituted phenylamino)cyclohex-2-enones and2-(substituted phenylamino)cyclohept-2-enones were prepared by known methodsthrough several steps, using cyclohexanone, cycloheptanone and substituted anilines.These two kinds of starting materials were treated with PIFA in Ac2O or TFE, leadingto the corresponding products quickly and smoothly. With the optimized reactionconditions, we constructed a series of tetrahydro-1H-carbazol-1-ones and analogs.And then the possible mechanisms involving the reaction process were studied andone most reasonable process was proposed.A variety of functionalized tetrahydro-1H-carbazol-1-ones and analogs weresynthesized through this method. And for all these obtained tetrahydro-1H-carbazol-1-ones and analogs, they were all well characterized by HRMS,1H&13C NMR spectroscopy.