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.