The environmentally friendly direct sulfenylation of indoles with thiols was performed by a unique coupled redox organocatalysis system using flavin and iodine.

A green, aerobic sulfenylation of imidazo[1,2- a]pyridines was performed using thiols, a flavin-and-iodine dual catalytic system, and environmentally benign molecular oxygen as the only sacrificial reagent. The dual metal-free catalysts smoothly promote a unique stepwise tandem process, beginning with the aerobic oxidation of a thiol to afford a disulfide that is utilized in the oxidative sulfenylation of the imidazo[1,2- a]pyridine. This process has afforded diverse 3-sulfenylimidazo[1,2- a]pyridines of biological interest and is environmentally friendly, as benign HO is the only byproduct.

Two-component metal-free catalytic oxidative sulfenylation of pyrazolones with thiols has been achieved using the biomimetic flavin and iodine. The methodology is mild and eco-friendly, proceeds in the presence of air or molecular oxygen (1 atm) as the sole sacrificial reagent, and generates water as the only byproduct. The methodology was also extended to the sulfenylation of pyrazoles and electron-rich benzenes and afforded a series of thioethers in good yields.

Herein, we report an aerobic oxidative C−N bond-forming process that enables the facile synthesis of imidazo[1,2a]pyridines and takes advantage of a coupled organocatalytic system that uses flavin and iodine. Furthermore, the dual catalytic system can be applied to the one-pot, three-step synthesis of 3-thioimidazo[1,2-a]pyridines from aminopyridines, ketones, and thiols.

The aerobic oxidative cross-coupling of indoles with azoles driven by flavin-iodine-coupled organocatalysis has been developed for the green synthesis of 2-(azol-1-yl)indoles. The coupled organocatalytic system enabled the one-pot threecomponent synthesis of 2-azolyl-3-thioindoles from indoles, azoles, and thiols in an atom-economical manner by utilizing molecular oxygen as the only sacrificial reagent.