Cp*Ir-Catalyzed Acceptorless Dehydrogenation of Carbon–Carbon Single Bonds

Pentamethylcyclopentadienyl (Cp*) iridium(III) chloride catalyzed acceptorless dehydrogenation of α-tetralone is reported. Cp* iridium chloride showed higher activity in comparison to other Cp* iridium complexes having bromide, iodide, or hydride or complexes without a Cp ring. The desired product, naphthol, was obtained in up to 71% yield from α-tetralone. The dehydrogenation by Cp* iridium catalyst could be applied to not only α-tetralone but also dihydrocoumarin, dihydroquinolinone, dimethylcyclohexanone, dihydrobenzofuran and 1-isochromanone, although the conversion stayed moderate. The catalytic turnover was not limited by the increased concentration of the product but by catalyst decomposition.