Electrochemical DABCOylation enables challenging aromatic C-H amination.

The selective amination of aromatic C-H bonds is a powerful strategy to access aryl amines, functionalities found in many pharmaceuticals and agrochemicals. Despite advances in the field, a platform for the direct, selective C-H amination of electronically diverse (hetero)arenes, particularly electron-deficient (hetero)arenes, remains an unaddressed fundamental challenge. In addition, many (hetero)arenes present difficulty in common selective pre-functionalization reactions, such as halogenation , or metal-catalyzed borylation and silylation .

Site-Selective Electrochemical Arene C-H Amination.

Here we present the discovery and development of a highly selective aromatic C-H amination reaction. This electrochemical strategy involves a cathodic reduction process that generates highly electrophilic dicationic -centered radicals that can efficiently engage in aromatic C-H functionalization and channel the regioselectivity of the aromatic substitution. The nitrogen-radical cation-pi interaction with arenes used throughout nature leads to a charge transfer mechanism, with subsequent aromatic C-N bond formation.

Late-Stage Heteroarylation of Hetero(aryl)sulfonium Salts Activated by α-Amino Alkyl Radicals.

We report a late-stage heteroarylation of aryl sulfonium salts through activation with α-amino alkyl radicals in a mechanistically distinct approach from previously reported halogen-atom transfer (XAT). The new mode of activation of aryl sulfonium salts proceeds in the absence of light and photoredox catalysts, engaging a wide range of hetarenes. Furthermore, we demonstrate the applicability of this methodology in synthetically useful cross-coupling transformations.

-Substitutions at Five-Membered Hetarenes Enabled by Sulfonium Salts.

We report a nucleophilic substitution reaction of five-membered hetarylsulfonium salts that results in a change of the substitution pattern on the arene. The products of these -substitutions are hard to access synthetically otherwise. The sulfonium salts that serve as starting materials are generated by a highly site-selective C-H functionalization reaction.

Site-Selective C-H Functionalization-Sulfination Sequence to Access Aryl Sulfonamides.

Aryl sulfinates are precursors to a diverse number of sulfonyl-derived arenes, which are common motifs in pharmaceuticals and agrochemicals. Here, we report a site-selective two-step C-H sulfination sequence via aryl sulfonium salts to access aryl sulfonamides. Combined with site-selective aromatic thianthrenation, an operationally simple one-pot palladium-catalyzed protocol introduces the sulfonyl group using sodium hydroxymethylsulfinate (Rongalite) as a source of SO.

Radical Carbofluorination of Alkenes with Arylhydrazines and Selectfluor: Additives, Mechanistic Pathways, and Polar Effects.

Radical carbofluorination reactions starting from arylhydrazines and nonactivated alkenes, in which the C-F bond is formed through the use of Selectfluor, can be improved through the addition of anisole. Because direct trapping products could be detected only in trace amounts, anisole does primarily act as a reversible scavenger for the highly reactive ammonium radical dication released from Selectfluor in the C-F bond-forming step. As shown for three diverse substitution patterns, the main role of anisole is to prevent, or at least reduce, the undesired addition of the ammonium radical dication to the alkene, which in turn leads to an unfavorable consumption of the arylhydrazine-derived precursors required for carbofluorination.