Heterogeneously Catalyzed Domino Synthesis of 3-Indolylquinones Involving Direct Oxidative C–C Coupling of Hydroquinones and Indoles

[Image: see text] A domino synthesis of 3-indolylquinones was achieved successfully via direct oxidative C–C coupling of hydroquinones with indoles over Ag(2)O and Fe(3)O(4)/povidone–phosphotungstic acid (PVP–PWA) catalysts using H(2)O(2) in tetrahydrofuran at room temperature. Ag(2)O catalyzed the in situ oxidation of hydroquinone and 3-indolylhydroquinone intermediates, whereas ferrite solid acid, Fe(3)O(4)/PVP–PWA, with a 1:4:1 ratio of Fe(3)O(4), PVP, and PWA, catalyzed the activation of quinones. The efficiency of this catalytic domino approach was established by a broad scope of substrates involving a variety of hydroquinones and quinones to give high yields (81–97%) of 3-indolylquinones. Fe(3)O(4)/PVP–PWA was separated magnetically, whereas simple filtration could separate Ag(2)O, both of which could be recycled several times without losing their activities.