Practical Electro-Oxidative Sulfonylation of Phenols with Sodium Arenesulfinates Generating Arylsulfonate Esters

Glyoxylic acid monohydrate promoted reductive addition of sodium sulfinates to pillar[4]arene[1]quinone

An efficient synthesis of sulfonate esters through reductive addition of sodium sulfinates to pillar[4]arene[1]quinone has been established (15 examples). Compared to the arylsulfonylation of p-quinone with sodium arylsulfinates under other acidic conditions, this work affords the hydroquinone-type 4-O-sulfonyl derivatives by using glyoxylic acid monohydrate as a promoter. The protocol features mild reaction conditions and high selectivity and is an alternative protocol for the O-sulfonylation of pillar[4]arene[1]hydroquinone.

Electrochemical Sulfonylation of Indoles with Inorganic Sulfites and Alcohols: Direct Synthesis of Indole Sulfonic Esters

A direct electrochemical sulfonylation between indoles, inorganic sulfites, and alcohols was developed, in which various indoyl sulfonate esters were prepared efficiently. In this transformation, the easy-handle and cost-effective inorganic sulfite was disclosed to engage in a Csp2-H sulfonylation as the SO2 source in an undivided electrolysis cell under mild conditions. In addition, the unexpected paired electrosynthesis has been achieved, owing to the dual role of inorganic sulfites, and led to a sulfonylation/reduction sequence to rapidly deliver hydroxyl substituted indole sulfonate esters.

Substrate-Controlled Electrochemical Reaction of 2-Alkynylbenzamides, Inorganic Sulfites, and Alcohols

Isoindolones constitute a dominant structural class in synthetic and medicinal chemistry. In this research, an electrochemical reaction involving 2-alkynylbenzamides, inorganic sulfites, and alcohols was first established to provide sulfonyl ester-substituted 3-hydroxyisoindolinone derivatives in moderate to good yields with excellent functional group tolerance. When bulky aryl-substituted 2-alkynylbenzamides are utilized as substrates, sulfonyl ester-substituted 3-alkylideneisoindolinones can be selectively generated with good chemoselectivity. Alkoxysulfonyl radicals derived from the anodic oxidation of inorganic sulfite with alcohols are involved in this transformation.

Electrochemical-induced phosphorylation of arenols and tyrosine containing oligopeptides

A disclosed technique employs electrochemical dehydrogenative cross-coupling to create organophosphates, utilizing phosphites compounds with arenols. Inorganic iodide salts serve dual roles as redox catalysts and electrolytes in an undivided cell, omitting the need for external oxidants or bases. Initial mechanistic investigations indicate the reaction unfolds via an electro-oxidative radical pathway, facilitating the formation of P-O bonds, leading to the generation of oxygen radicals in the formation of acetylaminophenol. This environmentally friendly approach offers excellent tolerance to various functional groups, achieves high yields (up to 95% isolated yield), and accommodates a wide range of substrates, showcasing its utility for practical synthesis applications.

Oxysulfonylation of Alkynes with Sodium Sulfinates to Access β-Keto Sulfones Catalyzed by BF3·OEt2

An efficient and operationally simple method for the synthesis of β-keto sulfones through the BF3·OEt2-promoted reaction of alkynes and sodium sulfinates is developed. With its facile and selective access to the targets, it features good functional group compatibility, mild conditions, easily available starting materials, and good yields. Notably, the reaction does not require metal catalysts or chemical reagents with pungent odors.

Highly efficient esterification of carboxylic acids with O-H nucleophiles through acid/iodide cooperative catalysis

The esterification of carboxylic acids is an important reaction for preparing esters which find wide applications in various research fields. In this manuscript, we report an acid/iodide cooperative catalytic method which enables highly efficient esterification of carboxylic acids with a wide range of equivalent O-H nucleophiles including both alcohols and weak nucleophilic phenols. Under the reaction conditions, both aromatic and aliphatic carboxylic acids including those bearing functional groups work well, furnishing the corresponding esters in good to high yields. Moreover, this reaction is scalable and applicable to the modification of bioactive molecules. These results demonstrate the synthetic value of this new reaction in organic synthesis.

Redox Relay-Induced C-S Radical Cross-Coupling Strategy: Application in Nontraditional Site-Selective Thiocyanation of Quinoxalinones

Oxidative cross-coupling is a powerful strategy to form C-heteroatom bonds. However, oxidative cross-coupling for constructing C-S bond is still a challenge due to sulfur overoxidation and poisoning transition-metal catalysts. Now, electrochemical redox relay using sulfur radicals formed in situ from inorganic sulfur source offers a solution to this problem. Herein, electrochemical redox relay-induced C-S radical cross-coupling of quinoxalinones and ammonium thiocyanate with bromine anion as mediator is presented. The electrochemical redox relay comprised initially the formation of sulfur radical via indirect electrochemical oxidation, simultaneous electrochemical reduction of the imine bond, electro-oxidation-triggered radical coupling involving dearomatization-rearomatization, and the reformation of the imine bond through anodic oxidation. Applying this strategy, various quinoxalinones bearing multifarious electron-deficient/-rich substituents at different positions were well compatible with moderate to excellent yields and good steric hindrance compatibility under constant current conditions in an undivided cell without transition-metal catalysts and additional redox reagents. Synthetic applications of this methodology were demonstrated through gram-scale preparation and follow-up transformation. Notably, such a unique strategy may offer new opportunities for the development of new quinoxalinone-core leads.

Metal-Free Oxidative Formation of Aryl Esters by Catalytic Coupling of Acyl and Sulfonyl Chlorides with Arylboronic Acids

A practical and efficient synthesis of aryl esters was developed through metal-free oxidation. This reaction employs stable and readily available acyl or sulfonyl chlorides and arylboronic acids as the starting materials and proceeds under mild reaction conditions without additional precious metal catalysts. This new strategy exhibits broad substrate tolerance and operational simplicity and gives diverse aryl esters in moderate to high yields.

Convenient Synthesis of Salicylanilide Sulfonates from 1,2,3-Benzotriazin-4(3H)-ones and Organosulfonic Acids via Denitrogenative Cross-Coupling

An efficient and straightforward approach to synthesize salicylanilide aryl and alkyl sulfonates from 1,2,3-benzotriazin-4(3H)-ones and organosulfonic acids is described. This protocol is operationally simple and scalable, exhibits a broad substrate scope with high functional group tolerance, and affords the desired products in good to high yield. Application of the reaction is also demonstrated by converting the desired product to synthetically useful salicylamides in high yields.

Copper-assisted preparation of pyridinyl sulfonate esters from hydroxypyridines and sodium sulfinates

An efficient and powerful copper-assisted method for the effective conversion of a broad range of hydroxypyridines and sodium sulfinates into their corresponding pyridinyl tosylates was developed. Key features of this base- and ligand-free protocol include using the cheap and readily available CuBr2 as a medium and the use of sodium sulfinates as formal sulfonylation reagents. A variety of functional pyridinyl tosylates could be formed with good yields, which can easily be converted into C-C and C-N bond-containing compounds.

Electro-oxidation induced O–S cross-coupling of quinoxalinones with sodium sulfinates for synthesizing 2-sulfonyloxylated quinoxalines

The novel C2–O sulfonylation of quinoxalinones via electro-oxidation induced O–S coupling strategy under mild conditions was reported.

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.