Efficient Synthesis of Indole Derivatives via Tandem Cyclization Catalyzed by Magnetically Recoverable Palladium/Magnetite (Pd‐Fe 3 O 4 ) Nanocrystals

Palladium-Catalyzed Tandem Nucleophilic Addition/C-H Functionalization of Anilines and Bromoalkynes for the Synthesis of 2-Phenylindoles

A novel and efficient palladium-catalyzed annulation of anilines with bromoalkynes for the synthesis of 2-phenylindoles has been described. This approach features excellent regio- and stereoselectivities and good functional group tolerance. Preliminary mechanistic studies indicate that anilines undergo anti-nucleophilic addition to bromoalkynes to generate (Z)-N-(2-bromo-1-phenylvinyl) anilines, followed by sequential C-H functionalization to deliver different substituted 2-phenylindoles. This method provides potential applications for the construction of various biologically active compounds.

One-pot C-C, C-N, and C-S bond construction for synthesis of 3-sulfenylindoles directly from unactivated anilines involving dual palladium catalysis and mechanistic insights from DFT

An efficient dual Pd-catalytic system was developed for one-pot synthesis of 3-sulfenylindoles via C-C, C-N and C-S bond construction directly from unactivated 2-iodo(NH)anilines under mild reaction conditions. Furthermore, 3-selenyl/halo/carbon-functionalized indoles were synthesized in good yields and a short reaction time. The synthetic utility of 3-sulfenylindole was also demonstrated. The key role of solvent in palladium catalysis was unravelled by DFT.

Aromatic Ketone-Catalyzed Photochemical Synthesis of Imidazo-isoquinolinone Derivatives

We have developed an efficient photocatalytic decarboxylative radical addition/cyclization strategy to synthesize imidazo-isoquinolinone derivatives using inexpensive aromatic ketone photocatalysts. This method not only tolerates a wide range of functional groups but also works well for both alkyl and aryl radicals.

Oxidative N-Formylation of Secondary Amines Catalyzed by Reusable Bimetallic AuPd-Fe3O4 Nanoparticles

Bimetallic catalysts are gaining attention due to their characteristics of promoting reactivity and selectivity in catalyzed reactions. Herein, a new catalytic N-formylation of secondary amines using AuPd–Fe₃O₄ at room temperature is reported. Methanol was utilized as the formyl source and 1.0 atm of O₂ gas served as an external oxidant. The bimetallic catalyst, consisting of Au and Pd, makes the reaction more efficient than that using each metal separately. In addition, the catalyst can be effectively recycled owing to the Fe₃O₄ support.

Chemoselective cyclization of 3-arylamino-2-hydroxy-tetrahydroindol-4-one in water at room temperature

A convenient and green protocol is developed for the chemoselective synthesis of indole derivatives by the one-pot, multi-component reaction of 5,5-dimethyl-3-(arylamino)cyclohex-2-enone derivatives (derived from the addition of various anilines to dimedone) with phenylglyoxal monohydrate, and diverse anilines, in water at room temperature. Advantages of this reaction include the availability of starting materials, use of water as a green solvent, catalyst-free approach, simple work-up, high yields, and preparation of potentially bioactive compounds.

Synthesis of Indoles and Benzofurans Using a Graphene Oxide-Grafted Aminobisphosphine-PdII Complex

Indoles and benzofurans have been synthesized using a graphene oxide-grafted aminobisphosphine-Pd^II complex (GO@PNP-Pd) under copper-free condition. A range of indole and benzofuran derivatives have been made by the reaction of N-protected 2-iodoanilines and 2-iodophenols with terminal acetylenes in presence of GO@PNP-Pd. The activity of the aminobisphosphine-Pd^II complex remains the same under both homogeneous and heterogeneous conditions. Finally, the recycling ability of the immobilized catalyst (GO@PNP-Pd) has been examined for five consecutive runs with appreciable conversion.

A copper(ii)-catalyzed annulative formylation of o-alkynylanilines with DMF: a single-step strategy for 3-formyl indoles

In this paper, a copper(ii)-catalyzed reaction of o-alkynylanilines with dimethylformamide (DMF) in the presence of oxygen has been developed for synthesizing multisubstituted 3-formyl indole scaffolds.