Indoxyl-based umpolung strategy for the synthesis of unsymmetrical 3,3′-biindoles

Azo Coupling of Indoles Revisited: Synthesis of Biindolyl Photoswitches via the Azo-Coupling/C-H Functionalization Domino Approach

When azo coupling of aryldiazonium salts with indoles was carried out in aprotic nonpolar solvent on air, a pseudo-three-component reaction has been discovered. Azo coupling is followed by a nucleophilic addition of a second indole unit to the indolium intermediate; aromatization and oxidation are achieved under air.

Accessing indole-isoindole derivatives via palladium-catalyzed [3+2] cyclization of isocyanides with alkynyl imines

A facile protocol for the preparation of indole-isoindole derivatives was developed and proceeds via a palladium-catalyzed [3+2] cyclization of isocyanides with alkynyl imines. In this transformation, the palladium catalyst has a triple role, serving simultaneously as a π acid, a transition-metal catalyst and a hydride ion donor, thus enabling the dual function of isocyanide both as a C1 synthon for cyanation and a C1N1 synthon for imidoylation. Significantly, the reaction is the sole successful example for accessing indole-isoindole derivatives, and will open up new avenues to assemble unique N-heterocycle frameworks. Furthermore, the synthetic value of this protocol is demonstrated in the late-stage modification of physiologically active molecules and in the construction of aggregation-induced emission compounds.

Anodic C(sp3)-H Acyloxylation of Indolin-3-ones Enabled by Oxidant-Free Cross-Dehydrogenative C(sp3)-O Coupling

An efficient anodic C(sp³)-H acyloxylation protocol has been established via intermolecular cross-dehydrogenative C(sp³)-O coupling. The protocol provides various C2-acyloxy indolin-3-ones without the addition of metal catalysts and external oxidants because indolin-3-ones can be directly oxidized at the anode. The effective application of several medical drugs and the realization of the gram-scale experiment have proven the practicality of this protocol.

2,3-Dimethoxyindolines: a latent electrophile for SNAr reactions triggered by indium catalysts

An unprecedented utilization of 2,3-dimethoxyindolines (DiMeOINs) as a latent electrophile in regioselective In-catalyzed aromatic substitutions has been reported.