Ir(III)-Catalyzed Oxidative Coupling of NH Isoquinolones with Benzoquinone

The oxidative coupling reactions of NH isoquinolones with 1,4-benzoquinone proceeded efficiently to form spiro compounds in the presence of an Ir­(III) catalyst through C–H activation. The reactions have a broad range of substrates, with nearly quantitative yields, without the use of external oxidants. For 1,4-naphthoquinone and other substituted 1,4-benzoquinone substrates the reactions also gave high yields with Cu­(OAc)2·H2O as an external oxidant. A catalytically competent five-membered iridacycle has been isolated and structurally characterized, thus revealing a key intermediate in the catalytic cycle.