Radical chain monoalkylation of pyridines

Bridge Heteroarylation of Bicyclo[1.1.1]pentane Derivatives

Herein, we report the decarboxylative Minisci heteroarylation of bicyclo[1.1.1]pentane (BCP) and 2-oxabicyclo[2.1.1]hexane (oBCH) derivatives at the bridge positions. In an operationally simple, photocatalyst-free process, free bridge carboxylic acids are directly coupled with nonprefunctionalized heteroarenes to provide rare examples of polysubstituted BCP and oBCH derivatives in synthetically useful yields. Additionally, the impact of the BCP core on the physicochemical properties of a representative example compared to those of its all-aromatic ortho- and meta-substituted analogues is evaluated.

Phototriggered Self-Catalyzed Three-Component Minisci Reaction: A Route to β-C(sp3) Heteroarylated Alcohols/Ethers

Herein, a visible-light-triggered photocatalyst-free radical cascade Minisci reaction of heteroarenes, alkenes, and water/alcohols to obtain diverse β-C(sp³) heteroarylated alcohols/ethers has been developed. Achieved under mild and simple conditions, this protocol is scalable and features broad substrate scope and functional group tolerance. Mechanistic studies demonstrate that the heteroarene can be served as a photocatalyst to engage single-electron transfer with persulfate.

Alkyl/Glycosyl Sulfoxides as Radical Precursors and Their Use in the Synthesis of Pyridine Derivatives

We report here the use of simple and readily available alkyl sulfoxides as precursors to radicals and their application in the preparation of pyridine derivatives. We show that alkyl sulfoxides, N-methoxy pyridinium salts and fluoride anions form electron donor-acceptor (EDA) complexes in solution, which, upon visible light irradiation, undergo a radical chain process to afford various pyridine derivatives smoothly. This reaction displays broad scope with respect to both sulfoxides and N-methoxy pyridiniums. The synthetic versatility of sulfoxides as a handle in chemistry adds to their power as radical precursors. Glycosyl sulfoxides are converted to the corresponding pyridyl C-glycosides with high stereoselectivities. Computational and experimental studies provide insights into the reaction mechanism.

Visible-Light-Catalyzed Tandem Radical Addition/1,5-Hydrogen Atom Transfer/Cyclization of 2-Alkynylarylethers with Sulfonyl Chlorides

A novel visible-light-catalyzed tandem radical addition/1,5-hydrogen atom transfer/cyclization cascade of 2-alkynylarylethers with sulfonyl chlorides in 2-methyltetrahydrofuran was developed under photocatalyst- and additive-free conditions. This reaction relies on unique energy transfer and solvent-radical relay strategies to generate sulfonyl radicals for the preparation of a series of sulfonyl-functionalized dihydrobenzofurans in moderate to high yields catalyzed by visible light or solar radiation.