Direct Synthesis of α-Sulfenylated Ketones under Electrochemical Conditions.

We investigated the electrochemical sulfenylation reaction in both batch and continuous flow regimes, involving thiophenols/thiols and enol-acetates to yield α-sulfenylated ketones, without using additional oxidants or catalysts. Studies with different electrolytes were also performed, revealing that quaternary ammonium salts are the best mediators for this reaction. Notably, during the study of the reaction scope, a Boc-cysteine proved to be extremely tolerant to our protocol, thus increasing its relevance. The methodology also proved to be scalable in both batch and continuous flow conditions, opening up possibilities for further studies since these relevant functional groups are important moieties in organic synthesis.

Sulfonyl Fluoride Synthesis through Electrochemical Oxidative Coupling of Thiols and Potassium Fluoride.

Sulfonyl fluorides are valuable synthetic motifs for a variety of applications, among which sulfur(VI) fluoride exchange-based "click chemistry" is currently the most prominent. Consequently, the development of novel and efficient synthetic methods to access these functional groups is of great interest. Herein, we report a mild and environmentally benign electrochemical approach to prepare sulfonyl fluorides using thiols or disulfides, as widely available starting materials, in combination with KF, as an inexpensive, abundant and safe fluoride source. No additional oxidants nor additional catalysts are required and, due to mild reaction conditions, the reaction displays a broad substrate scope, including a variety of alkyl, benzyl, aryl and heteroaryl thiols or disulfides.

Photoarylation of Pyridines Using Aryldiazonium Salts and Visible Light: An EDA Approach.

A metal-free methodology for the photoarylation of pyridines, in water, is described giving 2 and 4-arylated-pyridines in yields up to 96%. The scope of the aryldiazonium salts is presented showing important results depending on the nature and position of the substituent group in the diazonium salt, that is, electron-donating or electron-withdrawing in the ortho, meta, or para positions. Further heteroaromatics were also successfully photoarylated. Mechanistic studies and comparison between our methodology and similar metal-catalyzed procedures are presented, suggesting the occurrence of a visible-light EDA complex which generates the aryl radical with no need for an additional photocatalyst.