Herein, we report a greener protocol for the synthesis of 3-Se/S-indoles and imidazo[1,2-a]pyridines through direct C(sp2 )-H bond chalcogenation of heteroarenes with half molar equivalents of different dichalcogenides, using KIO3 as a non-toxic, easy-to-handle catalyst and a stoichiometric amount of glycerol. The reaction features are high yields, based on atom economy, easy performance on gram-scale, metal- and solvent-free conditions as well as applicability to different types of N-heteroarenes.

Direct, Metal-free C(sp2 )-H Chalcogenation of Indoles and Imidazopyridines with Dichalcogenides Catalysed by KIO3.

In this report, the highly efficient Rose Bengal-catalysed C(sp2)-H selenylation of indoles, imidazoles and arenes was achieved using a half molar equiv. of diorganoyl diselenides. This metal-free, photo-induced protocol resulted in selenylated products in good to excellent yields. The reaction features are high yields, an atom-economic, gram-scalable and metal-free approach, and applicability to different biologically relevant (hetero)arenes.

Rose Bengal catalysed photo-induced selenylation of indoles, imidazoles and arenes: a metal free approach.

Visible-light-induced metal and reagent-free oxidative coupling of sp2 C–H bonds with organo-dichalcogenides: synthesis of 3-organochalcogenyl indoles

A copper-mediated direct C3 amination of imidazopyridines has been disclosed under additive-free conditions in short reaction times. This methodology utilizes commercially available N-fluorobenzenesulfonimide (NFSI) as the amino source, which exhibits broad substrate scope and good functional group tolerance. The obtained C3-aminated imidazopyridines can undergo further desulfonylation transformations. Control experiments suggest that this reaction probably proceeds via a free-radical mechanism. Moreover, NFSI also shows potential application in C-H fluorination of imidazopyridines.

Copper-Mediated C-H Amination of Imidazopyridines with N-Fluorobenzenesulfonimide.

A convenient and efficient oxidative dual C–H selenation radical reaction of imidazoheterocycles with ethers or alkanes using selenium powder was developed with moderate to good yields. This procedure provides a wide range of valuable and structurally diverse 3-alkylselanyl-imidazoheterocycle derivatives with broad substrate scope, excellent functional group tolerance and high efficiency.

Lais T. Silva

Papers

Direct, Metal-free C(sp2 )-H Chalcogenation of Indoles and Imidazopyridines with Dichalcogenides Catalysed by KIO3.

Solvent- and Metal-Free Chalcogenation of Bicyclic Arenes Using I2/DMSO as Non-Metallic Catalytic System

Copper‐Catalyzed Three‐Component Reaction of Oxadiazoles, Elemental Se/S and Aryl Iodides: Synthesis of Chalcogenyl (Se/S)‐Oxadiazoles