Electrochemical Radical δ-H Sulfonylation Reaction for the Synthesis of 4-((Aryl,Arylsul fonyl)methylene)-2,5-Cyclohexadiene Derivatives

Iron-Catalyzed Cross-Dehydrogenative Coupling of para-Quinone Methides with Formamides: In Situ Activation of C(sp2)-H Bonds

A novel and straightforward method for the iron-catalyzed regioselective cross-dehydrogenative coupling of para-quinone methides (p-QMs) with formamides has been developed, facilitated by the in situ activation of the C(sp2)-H bonds of the formyl and alkenyl substituents via a radical strategy. This method does not require the preactivation of the substrates, and it can accommodate a wide range of p-QMs and formamides under the optimized reaction conditions, resulting in the formation of the expected C-7 acetamides-functionalized para-quinone methides with moderate to good yields. The control experiments revealed that the reaction follows the fundamental equation of second-order kinetics. Additionally, an exploration of the Hammett effect was undertaken to elucidate the impact of the substituents for the reaction. In combination with the DFT calculation, a plausible reaction mechanism was proposed through meticulously controlled experiments.

Electrochemical Selenized Reaction of N-Arylbicyclo[1.1.0]butane-1-carboxamides: Access to 3-(Arylselanyl)spiro[cyclobutane-1,3'-indolin]-2'-one Derivatives

A novel selenized reaction of N-arylbicyclo [1.1.0]butane-1-carboxamides with diselenide for the synthesis of polycyclic indoline derivatives is developed under electrochemical conditions. The synthesis is achieved by the bicyclo[1.1.0]butane strain-release reaction and intramolecular cyclization process. In addition, this approach features a wide range of substrates, good group tolerance, shorter reaction time, and mild conditions.

Electrochemical Sulfonylation/Cyclization of N-Alkenylacrylamides with Sodium Sulfinates or Sulfonyl Hydrazides

Two general protocols for the regioselective electrochemically enabled sulfonylation cyclization of N-alkenylacrylamides with sodium sulfinates or sulfonyl hydrazides were described. These methods were carried out under mild, chemical oxidant-free, and transition-metal-free conditions with a broad substrate scope and good functional group tolerance to provide sulfonyl-containing 4-pyrrolin-2-ones, which is readily scalable to the gram scale.

Electrochemical Oxidative Sulfonylation-Azidation of Alkenes

A novel electrochemical oxidative sulfonylation-azidation of alkenes is accomplished by using sulfonyl hydrazide and trimethylsilyl azide (TMSN3) for the one-pot and green synthesis of β-azidoarylsulfone, which involves the direct construction of new C-S and C-N bonds. Notably, neither exogenous oxidants/additives nor metal catalysts are required for this method. In addition, this electrochemical strategy features mild conditions and wide substrate scope and has been proved to be a radical pathway by mechanistic studies.

Electrochemical Radical Reaction Construction of C-C Bonds: Access to 1,4-Dicarbonyl Compounds from Enol Acetates and 1,3-Diketones

As important substrates for the construction of heterocycles, a simple and efficient approach for synthesis of 1,4-diones is highly desirable. In this work, novel and efficient electrochemical radical reactions of enol acetates and 1,3-diketones have been developed to successfully achieve 1,4-diketones under catalyst-free and oxidant-free conditions. The wide range of substrates, good group tolerance, and simple operation process make the approach have important practical value. Moreover, the obtained 1,4-diketones can be easily further transformed to pyrrole and furan derivatives.

Electrochemical Radical Reactions of Enol Acetates and Free Alcohols Directly Access to α-Alkoxylated Carbonyl Compounds

The efficient intermolecular alkoxylation reactions of various enol acetates and different alcohols are developed in the electrochemical process for the first time. Enol acetates derived from either aromatic, alkyl, or alicyclic ketones, and abundant free alcohols directly used in this synthetic strategy, make this transformation very valuable in synthesis and application in the future.

Fluorohydroxylation and Hydration Reactions of para-Quinone Methides Promoted by Selectfluor

Selectfluor-promoted vicinal fluorohydroxylation and hydration reaction of para-quinone methides (p-QMs) were described, affording vicinal fluorohydrins and ketone/ether products in high yields. The hydration products were highly controlled by the electronic properties of substituents in the aromatic ring, and simultaneously, the amount of Selectfluor was completely different during the synthesis of ketone/ether products. This reaction also represents the first fluorohydroxylation of p-QMs, and the wide range of p-QMs makes the vicinal fluorohydroxylation of great significance.

Electrochemical Synthesis of Dibenzothiophenes via Intramolecular C-S Cyclization with a Halogen Mediator

Electrochemical synthesis of dibenzothiophene derivatives was achieved. Several bis(biaryl) disulfides are efficiently converted to dibenzothiophenes by electrochemical oxidation. The use of Bu4NBr as a halogen mediator was essential, and wide varieties of dibenzothiophene derivatives were obtained in good yields.

Electrochemical Synthesis of 1,2,3-Thiadiazoles from α-Phenylhydrazones

We have developed an electrochemical approach for the synthesis of fully substituted 1,2,3-thiadiazoles from α-phenylhydrazones at room temperature, which is very challenging and complementary to the conventional thermal reactions. The key step involves anodic oxidation of phenylhydrazone derivatives at a constant current followed by N,S-heterocyclization. The protocol is remarkable in that it is free of a base and free of an external oxidant and can be converted to a gram scale for postsynthetic drug development with functional thiadiazoles. Most importantly, the electrochemical transformation reflected efficient electro-oxidation with an operationally friendly easy procedure with ample functional molecules. Cyclic voltammograms support the mechanism of this electro-oxidative cyclization process.

Electrochemical sulfonylation of enamides with sodium sulfinates to access β-amidovinyl sulfones

The electrochemical sulfonylation of enamides with sodium sulfinates was developed in an undivided cell in constant current mode, leading to the formation of β-amidovinyl sulfones in moderate to good yields. The catalyst-, electrolyte- and oxidant-free protocol features good functional group tolerance and employs electric current as a green oxidant. Mechanistic insights into the reaction indicate that the reaction may proceed via a radical mechanism.