Three-Component, Four-Molecule, Ru-Catalyzed Cascade Reactions of Indoles and Alkyl Bromides with Sodium Nitrite

<div><p></p><p>An operationally simple domino approach for the ruthenium-catalyzed synthesis of (<i>E</i>)-2,3′-bi(3<i>H</i>-indol)-3-one <i>O</i>-alkyl oximes by the region- and stereoselective three-component, four-molecule reactions of indoles with sodium nitrite and alkyl bromides under mild reaction condition in dimethylformamide is described. Remarkably, multiple bonds including C‒C, C=N, and C‒O bonds were conveniently formed in one pot. The reaction is tolerant to air and is atom economical, in accordance with the concept of modern green chemistry.</p></div

Cu₂O-Catalyzed C(sp³)-H/C(sp³)-H Cross-Coupling Using TEMPO: Synthesis of 3-(2-Oxoalkyl)-3-hydroxyoxindoles

<div><p></p><p>A simple, convenient and efficient oxidative cross-coupling reaction of oxindoles with ketones toward a variety of 3-(2-oxoalkyl)-3-hydroxyoxindoles in moderate to excellent yields has been developed. This transformation proceeds<i>via</i> a tandem oxidative cross-coupling by using TEMPO in air as an environmentally benign oxidant. This methodology provides an alternative approach for the direct generation of all-carbon quaternary centers at the C3 position of oxindoles.</p></div

Metal-Free–Catalyzed Oxidative Trimerization of Indoles Using NaNO₂ to Construct Quaternary Carbon Centers: Synthesis of 2-(1<i>H</i>-Indol-3-yl)-2,3′-biindolin-3-ones

<div><p></p><p>A simple, convenient, and efficient synthesis of 2-(1<i>H</i>-indol-3-yl)-2,3′-biindolin-3-one derivatives via a transition-metal-free-catalyzed oxidative trimeric reaction of indoles has been developed. This transformation may have occurred through a tandem oxidative homocoupling reaction by using NaNO₂ in pyridine as oxidant. This methodology provides an alternative approach for the direct generation of all-carbon quaternary centers at the C2 position of indoles.</p> </div