TsCl-promoted sulfonylation of quinoline N-oxides with sodium sulfinates in water

TsCl promoted deoxygenative phosphorothiolation of quinoline N-oxides towards S-quinolyl phosphorothioates

A convenient, efficient and practical approach for the synthesis of S-quinolyl phosphorothioates via cheap TsCl promoted deoxygenative C2-H phosphorothiolation of quinoline N-oxides with readily available triethylammonium O,O-dialkylphosphorothioates was developed. The reaction performed well under transition-metal-free conditions at room temperature with a very short reaction time (10-20 min). Preliminary studies showed that the current transformation underwent a nucleophilic substitution process.

Synthesis of Quinoline-2-thiones by Selective Deoxygenative C-H/C-S Functionalization of Quinoline N-Oxides with Thiourea

Quinoline-2-thiones valuable for synthetic and medicinal chemistry applications were obtained with excellent regioselectivity employing a deoxygenative C-H functionalization of readily available quinoline-N-oxides with thiourea upon activation with triflic anhydride. Unlike the current methods, this approach provides general access to diverse quinoline-2-thiones functionalized with groups of different electronic natures. Experimental simplicity and good to high yields are advantages of this protocol. Given the high reactivity of quinoline-2-thiones, this method provides an entry point for the synthesis of diverse organosulfur quinoline scaffolds.

Copper(I)-Catalyzed Three-Component Selenosulfonation of Maleimides with Sulfonyl Hydrazides and Diselenides via Radical Relay

By employing Cu(CH₃CN)₄PF₆ as the catalyst and tert-butyl hydroperoxide as the oxidant, we realized a three-component radical selenosulfonation of substituted maleimides, sulfonyl hydrazides, and diphenyl diselenides, providing a series of 3,4-selenosulfonylated succinimides in moderate to good yields. This reaction features broad substrate scopes, high functional-group tolerability, and feasibility of gram-scale synthesis, enabling one-step construction of C-SO₂ and C-Se bonds under mild reaction conditions. Preliminary mechanistic studies support the free-radical-induced pathway.

Synthesis of Quinoline Silyloxymethylsulfones as Intermediates to Sulfonyl Derivatives

Heterocyclic sulfones, sulfonamides, and sulfonyl fluorides constitute an important structural motif in medicinal chemistry. Methods to make six-membered heteroaromatic sulfonyl compounds, however, remain challenging, and most efforts rely on commercial sulfonyl chlorides. We report herein the reaction of sodium tert-butyldimethyl silyloxymethylsulfinate with quinoline N-oxides to selectively furnish C2-substituted sulfones. The silyloxymethylsulfinate can be deprotected to then form sulfonyl fluorides, sulfonamides, and sulfones. This transformation is scalable and has broad applicability to a wide array of quinoline and isoquinoline functionality.

Photoredox Neutral Decarboxylative Hydroxyalkylations of Heteroarenes with α-Keto Acids

Photoredox neutral decarboxylative hydroxyalkylations of heteroarenes with α-keto acids under mild conditions are described. Stable and readily available α-keto acids were employed as hydroxyalkylating reagents with only CO₂ released as the byproduct. A range of aromatic and aliphatic α-keto acids were successfully converted into hydroxyalkylated products with various heteroarenes. This transformation proceeded through a decarboxylation/Minisci addition/SCS sequence, generating a variety of valuable hydroxyalkylated heteroarenes.

Transition-Metal-Free Radical-Triggered Hydrosulfonylation and Disulfonylation Reaction of Substituted Maleimides with Sulfonyl Hydrazides

A convenient and practical hydrosulfonylation and disulfonylation of substituted maleimides was realized using sulfonyl hydrazides as the sulfur reagent and tert-butyl hydroperoxide as the oxidant. The advantages of the reactions include mild and transition-metal-free reaction conditions, good functional group tolerance, and readily available starting materials. The radical species-induced pathway is also demonstrated by mechanistic studies.

Visible-light mediated cross-coupling of aryl halides with sodium sulfinates via carbonyl-photoredox/nickel dual catalysis

Photoinduced nickel-catalyzed cross-coupling of arylsulfinates (ArSO2−) with (hetero)aryl halides (Ar’-X) via visible light photoexcitation of 2-chloro-thioxanthen-9-one (Cl-TXO) has been achieved in moderate to excellent yields. This photocoupling exhibited a broad...

TsCl-promoted thiolation of quinoline N-oxides with thiophenols

A metal- and oxidant-free method for the synthesis of various 2-thioquinolines through p-toluenesulfonyl chloride-promoted thiolation reaction of quinoline N-oxides with thiophenols in water at an ambient temperature is developed.

Recent Progress and Emerging Technologies towards a Sustainable Synthesis of Sulfones

Sulfones play a pivotal role in modern organic chemistry. They are highly versatile building blocks and find various applications as drugs, agrochemicals, or functional materials. Therefore, sustainable access to this class of molecules is of great interest. Herein, the goal was to provide a summary on recent developments in the field of sustainable sulfone synthesis. Advances and existing limitations in traditional approaches towards sulfones were reviewed on selected examples. Furthermore, novel emerging technologies for a more sustainable sulfone synthesis and future directions were discussed.

Fluorination of 2H-Indazoles Using N-Fluorobenzenesulfonimide

An efficient, simple, and metal-free fluorination of 2H-indazoles has been developed using N-fluorobenzenesulfonimide (NFSI) in water under ambient air. This transformation provides direct access to fluorinated indazole derivatives with broad functionalities in satisfactory yields. The experimental results suggest a radical mechanistic pathway of this protocol.

Electrochemical-induced hydroxylation of aryl halides in the presence of Et3N in water

A thorough study of mild and environmentally friendly electrochemical-induced hydroxylation of aryl halides without a catalyst is presented. The best protocol consists of hydroxylation of different aryl iodides and aryl bromides by water solution in the presence of Et3N under air, affording the target phenols in good isolated yields. Moreover, aryl chlorides were successfully employed as substrates. This methodology also provides a direct pathway for the formation of deoxyphomalone, which displayed a significant anti-proliferation effect.

Synthesis and applications of sodium sulfinates (RSO2Na): a powerful building block for the synthesis of organosulfur compounds

This review highlights the preparation of sodium sulfinates (RSO2Na) and their multifaceted synthetic applications. Substantial progress has been made over the last decade in the utilization of sodium sulfinates emerging as sulfonylating, sulfenylating or sulfinylating reagents, depending on reaction conditions. Sodium sulfinates act as versatile building blocks for preparing many valuable organosulfur compounds through S-S, N-S, and C-S bond-forming reactions. Remarkable advancement has been made in synthesizing thiosulfonates, sulfonamides, sulfides, and sulfones, including vinyl sulfones, allyl sulfones, and β-keto sulfones. The significant achievement of developing sulfonyl radical-triggered ring-closing sulfonylation and multicomponent reactions is also thoroughly discussed. Of note, the most promising site-selective C-H sulfonylation, photoredox catalytic transformations and electrochemical synthesis of sodium sulfinates are also demonstrated. Holistically, this review provides a unique and comprehensive overview of sodium sulfinates, which summarizes 355 core references up to March 2020. The chemistry of sodium sulfinate salts is divided into several sections based on the classes of sulfur-containing compounds with some critical mechanistic insights that are also disclosed.

Nitriles as radical acceptors in radical cascade reactions

The application of the cyano group as a radical acceptor in the cascade reactions for the construction of various important heterocycles and carbocycles was summarized.

Iridium-catalyzed regioselective C–H sulfonamidation of 1,2,4-thiadiazoles with sulfonyl azides in water

We have developed a regioselective C–N cross-coupling of 1,2,4-thiadiazoles with sulfonyl azides through iridium catalysis in water. This method tactically linked the 1,2,4-thiadiazoles and sulfonamides together, and the novel molecules increased the diversity of 1,2,4-thiadiazoles which may have potential applications.

We have developed a regioselective C–N cross-coupling of 1,2,4-thiadiazoles with sulfonyl azides through iridium catalysis in water.

An efficient imidation of thioethers with nitrene in water

The first imidation of thioethers with free nitrene in water was realized. N-Cbz sulfilimines are formed via imidation of thioethers with free nitrene generated from α elimination of nosyloxycarbamates. In this work, water is successfully applied as solvent for free nitrene, and transition metal catalyst is not needed.

Copper(i)-catalyzed intermolecular cyanoarylation of alkenes: convenient access to α-alkylated arylacetonitriles

A novel Cu(i)-catalyzed intermolecular cyanoarylation of alkenes with diaryliodonium salts as a radical arylating reagent and tetra-butylammonium cyanide as an electrophilic cyanating reagent was established. A broad range of α-alkylated arylacetonitriles were efficiently constructed in good to excellent yields under base- and oxidant-free and mild conditions.

Transition metal- and catalyst-free one-pot green method for the synthesis of N-sulfonyl amidines via direct reaction of sulfonyl azides with amines

In this report, a green synthesis of N-sulfonyl amidines via the direct reaction of tertiary or secondary amines with sulfonyl azides is described. Transition metal- and catalyst-free conditions were used for the synthesis of biologically important N-sulfonyl amidines. Further studies showed that the reaction proceeded via in situ aerobic oxidation of amines under reflux conditions.