Iron-Catalyzed Sulfonylmethylation of Imidazo[1,2-α]pyridines with N,N-Dimethylacetamide and Sodium Sulfinates.

Functionalized imidazo[1,2-α]pyridines are important scaffolds in pharmaceuticals. Herein, we present an efficient 3-sulfonylmethylation protocol for imidazo[1,2-α]pyridines by sodium sulfinates in DMA and H2O (2:1) via an FeCl3-catalyzed three-component coupling reaction. Various sulfonylmethyl imidazo[1,2-α]pyridines were thus afforded in high yields with excellent functional group tolerance. A plausible oxidation-addition mechanism was proposed.

Synthesis of Asymmetric Diaryl Sulfides via HI-Mediated C(sp2)-H Sulfenylation of Arenes with Sodium Sulfinates.

A novel hydroiodic acid-promoted metal-free C(sp2)-H sulfenylation of electron-rich arenes was developed using stable and easy-to-handle sodium sulfinates as sulfur sources. Diverse kinds of asymmetric aryl sulfides were afforded in good yields from various commercially available aromatic substrates under mild conditions. Comprehensive mechanistic experiments demonstrate that RSO2SR and RSSR are the key intermediates responsible for the redox process.

Efficient Synthesis of 3-Mercaptoindoles via HI-Promoted Sulfenylation of Indoles with Sodium Sulfinates.

A new direct sulfenylation method of indoles by sodium sulfinates and hydroiodic acid was developed giving variety of 3-sulfenylindoles in high yields under mild conditions without using any catalysts or other additives. In situ-generated RS-I species are supposed to be mainly responsible for the key electrophilic alkyl- or aryl-thiolation process.