Photocatalytic Sulfonylation: Innovations and Applications

Photosynthesis, converting sustainable solar energy into chemical energy, has emerged as a promising craft to achieve diverse organic transformations due to its mild reaction conditions, sustainability, and high efficiency. The synthesis of sulfonated compounds has drawn significant attention in the pharmaceuticals, agrochemicals, and materials industries due to the unique structure and electronic properties of the sulfonyl groups. Over the past decades, many photocatalytic sulfonylation reactions have been developed. In this review, the recent advances in photocatalyzed sulfonylation have been reviewed since 2020, with a primary focus on discussing reaction design and mechanism.

Metal-free efficient synthesis of aryl sulfonamides from N-hydroxy sulfonamide and amines

A simple and novel approach has been developed for the synthesis of sulfonamides from N-hydroxy sulfonamide. Notably, the iodine-tert-butyl hydroperoxide (TBHP) system efficiently promoted the sulfonylation reactions of N-hydroxy sulfonamides and amines via the oxidative cleavage of an S-N bond. A variety of aryl sulfonamides were prepared in moderate to good yields using readily available starting materials and the biomass-derived 2-MeTHF solvent. The present method has the advantages of using metal-free reagents, an eco-friendly medium, cost-effective reagents, wide substrate scope, and mild conditions.

Selective Synthesis of Sulfonamides and Sulfenamides from Sodium Sulfinates and Amines

An effective method was explored for the selective synthesis of sulfonamides and sulfenamides using sodium sulfinates and amines as starting materials. This method offers mild reaction conditions, a broad substrate scope, high efficiency, and readily accessible materials, making it suitable and an alternative strategy for the preparation of a variety of biologically or pharmaceutically active compounds.

Bypassing Sulfonyl Halides: Synthesis of Sulfonamides from Other Sulfur-Containing Building Blocks

This review disclosed synthetic approaches to sulfonyl amides from non-sulfonyl halogenated precursors. Known methods were systematized into groups and subgroups according to the type of starting organosulfur compound. Thiols, disulfides, and sulfonamides form a group of S(II)-containing precursors, which are used in oxidative amination reactions. An important and versatile group for oxidative amination is represented with S(IV)-containing compounds, i. e., sufinates, sulfinamides, DMSO, N-sulfinyl-O-(tert-butyl)hydroxylamine, etc. A series of S(VI)-containing precursors for amination reactions (except sulfonyl halides) include sulfonic acids, sulfonyl azides, thiosulfonates, and sulfones. All approaches are represented with the most prominent examples of the resulting sulfonamides, which could be obtained in high yields mostly via short reaction sequences. Promising electrochemical methods for the preparation of sulfonamides from thiols, disulfides, sulfonamides, sulfinic acid derivatives, and dimethyl sulfoxide under mild and green conditions are also highlighted.

A new type of convergent paired electrochemical synthesis of sulfonamides under green and catalyst-free conditions

Our main goal in this work is to synthesize valuable sulfonamide compounds according to the principles of green chemistry and also to present a unique convergent paired mechanism for their synthesis. In this study, we introduced a new type of convergent paired electro-organic synthesis of sulfonamide derivatives via a catalyst, oxidant, halogen and amine-free method. In this research, instead of using toxic amine compounds, an innovative mechanism based on the reduction of nitro compounds and in-situ production of amine compounds was used. The mechanism of electrophile generation is the cathodic reduction of the nitro compound to the hydroxylamine compound and then the anodic oxidation of the hydroxylamine to the nitroso compound. On the other hand, the nucleophile generation mechanism involves the two-electron oxidation of sulfonyl hydrazide to related sulfinic acid at the anode surface. The reaction leading to the synthesis of sulfonamides involves a one-pot reaction of the generated nitroso compound with the produced sulfinic compound.

An Efficient Method for the Preparation of Sulfonamides from Sodium Sulfinates and Amines

Sulfonamides have a special role on medicine due to their broad biological activities, as bacterial infections, diabetes mellitus, oedema, hypertension prevention and treatment. In addition, sulfonamides are also useful in herbicides and pesticides. Herein, we communicate an efficient strategy for the preparation of sulfonamides via NH₄I‐mediated amination of sodium sulfinates. This new method provides a general and environmentally friendly access to sulfonamide compounds and tolerates a wide range of functional groups.

Palladium-Catalyzed Three-Component Dearomatization/Sulfonylation Cascade

The diastereoselective synthesis of sulfonylated indolines is reported. A palladium-catalyzed dearomative sulfination of (aza)indole-tethered aryl iodides generates reactive benzylic sulfinates. These intermediates react with electrophiles in a one-pot, two-step process to generate sulfonylated products in good yields and excellent diastereoselectivity. This three-component sequence demonstrates good scalability and can be applied toward the synthesis of sulfonamides. Additionally, further derivatizations of aryl iodide containing products furnish spiro- and alkynylated indoline products.

Photons or Electrons? A Critical Comparison of Electrochemistry and Photoredox Catalysis for Organic Synthesis

Redox processes are at the heart of synthetic methods that rely on either electrochemistry or photoredox catalysis, but how do electrochemistry and photoredox catalysis compare? Both approaches provide access to high energy intermediates (e.g., radicals) that enable bond formations not constrained by the rules of ionic or 2 electron (e) mechanisms. Instead, they enable 1e mechanisms capable of bypassing electronic or steric limitations and protecting group requirements, thus enabling synthetic chemists to disconnect molecules in new and different ways. However, while providing access to similar intermediates, electrochemistry and photoredox catalysis differ in several physical chemistry principles. Understanding those differences can be key to designing new transformations and forging new bond disconnections. This review aims to highlight these differences and similarities between electrochemistry and photoredox catalysis by comparing their underlying physical chemistry principles and describing their impact on electrochemical and photochemical methods.

Facile construction of C,N-disulfonated 5-amino pyrazoles through an iodine-catalyzed cascade reaction

A green and facile synthesis of previously unreported C,N-disulfonated 5-amino pyrazoles was established through an iodine-catalyzed cascade reaction.

A new method for C(sp2)-H sulfonylmethylation with glyoxylic acid and sodium sulfinates

We herein describe a C4 sulfonylmethylation of pyrazol-5-amines with glyoxylic acid and sodium sulfinates. The reaction only needed to add water as the solvent, and it featured mild reaction condition,...

PhI(OAc)2 and iodine-mediated synthesis of N-alkyl sulfonamides derived from polycyclic aromatic hydrocarbon scaffolds and determination of their antibacterial and cytotoxic activities

The development of new approaches toward chemo- and regioselective functionalization of polycyclic aromatic hydrocarbon (PAH) scaffolds will provide opportunities for the synthesis of novel biologically active small molecules that exploit the high degree of lipophilicity imparted by the PAH unit. Herein, we report a new synthetic method for C-X bond substitution that is speculated to operate via a N-centered radical (NCR) mechanism according to experimental observations. A series of PAH sulfonamides have been synthesized and their biological activity has been evaluated against Gram-negative and Gram-positive bacterial strains (using a BacTiter-Glo assay) along with a series of mammalian cell lines (using CellTiter-Blue and CellTiter-Glo assays). The viability assays have resulted in the discovery of a number of bactericidal compounds that exhibit potency similar to other well-known antibacterials such as kanamycin and tetracycline, along with the discovery of a luciferase inhibitor. Additionally, the physicochemical and drug-likeness properties of the compounds were determined experimentally and using in silico approaches and the results are presented and discussed within.

Transition Metal-Free De Novo Synthesis of Sulfonated Pyrazoles from Sulfonyl Hydrazides, 1,3-Diketones, and Sodium Sulfinates at Room Temperature

A transition metal-free method for de novo construction of diverse sulfonated pyrazoles from readily available sulfonyl hydrazides, 1,3-diketones, and sodium sulfinates was established under mild conditions. Pyrazoles bearing two different sulfonyl groups were obtained in one step. The method features a diversity of substituents of the pyrazole products and a remarkably simple work-up.

A Broad-Spectrum Catalytic Amidation of Sulfonyl Fluorides and Fluorosulfates*

A broad-spectrum, catalytic method has been developed for the synthesis of sulfonamides and sulfamates. With the activation by the combination of a catalytic amount of 1-hydroxybenzotriazole (HOBt) and silicon additives, amidations of sulfonyl fluorides and fluorosulfates proceeded smoothly and excellent yields were generally obtained (87-99 %). Noticeably, this protocol is particularly efficient for sterically hindered substrates. Catalyst loading is generally low and only 0.02 mol % of catalyst is required for the multidecagram-scale synthesis of an amantadine derivative. In addition, the potential of this method in medicinal chemistry has been demonstrated by the synthesis of the marketed drug Fedratinib via a key intermediate sulfonyl fluoride 13. Since a large number of amines are commercially available, this route provides a facile entry to access Fedratinib analogues for biological screening.

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.

Recent Advances in Iodine-Promoted C-S/N-S Bonds Formation

Sulfur-containing scaffold, as a ubiquitous structural motif, has been frequently used in natural products, bioactive chemicals and pharmaceuticals, particularly C-S/N-S bonds are indispensable in many biological important compounds and pharmaceuticals. Development of mild and general methods for C-S/N-S bonds formation has great significance in modern research. Iodine and its derivatives have been recognized as inexpensive, environmentally benign and easy-handled catalysts or reagents to promote the construction of C-S/N-S bonds under mild reaction conditions, with good regioselectivities and broad substrate scope. Especially based on this, several new strategies, such as oxidation relay strategy, have been greatly developed and accelerated the advancement of this field. This review focuses on recent advances in iodine and its derivatives promoted hybridized C-S/N-S bonds formation. The features and mechanisms of corresponding reactions are summarized and the results of some cases are compared with those of previous reports. In addition, the future of this domain is discussed.

Direct sulfonamidation of (hetero)aromatic C-H bonds with sulfonyl azides: a novel and efficient route to N-(hetero)aryl sulfonamides

N-Aryl sulfonamides belong to a highly important class of organosulfur compounds which are found in a number of FDA-approved drugs such as dofetilide, dronedarone, ibutilide, sotalol, sulfadiazine, sulfamethizole, vemurafenib, and many more. There is therefore continuing interest in the development of novel and convenient protocols for the preparation of these pharmaceutically important compounds. Recently, direct sulfonamidation of (hetero)aromatic C–H bonds with easily available sulfonyl azides has emerged as an attractive and powerful strategy to access N-(hetero)aryl sulfonamides where non-toxic nitrogen gas forms as the sole by-product. This review highlights recent advances and developments (2012–2020) in this fast growing research area with emphasis on the mechanistic features of the reactions.

N-Aryl sulfonamides belong to a highly important class of organosulfur compounds which are found in a number of FDA-approved drugs such as dofetilide, dronedarone, ibutilide, sotalol, sulfadiazine, sulfamethizole, vemurafenib, and many more.

Sequential C-S and S-N Coupling Approach to Sulfonamides

A one-pot three-component reaction involving nitroarenes, (hetero)arylboronic acids, and potassium pyrosulfite leading to sulfonamides was described. A broad range of sulfonamides bearing different reactive functional groups were obtained in good to excellent yields through sequential C-S and S-N coupling that does not require metal catalysts.

An update on the use of sulfinate derivatives as versatile coupling partners in organic chemistry

The use of sulfinic acids and their salts continues to be extensively developed in organic chemistry. This is attributable to their dual capacity for acting as nucleophilic or electrophilic reagents, as well as their ease of preparation and stability on storage. This report highlights the research accomplished since 2015 on this topic, updating a previous review published by our team in 2014.

The same oxygenation-state introduction of hypervalent sulfur under transition-metal-free conditions

This review discusses the application of the same oxygenation-state introduction of hypervalent sulfur strategy under transition-metal-free conditions.

TBAI-catalyzed selective synthesis of sulfonamides and β-aryl sulfonyl enamines: coupling of arenesulfonyl chlorides and sodium sulfinates with tert-amines

A simple, practical and metal-free method has been developed for the synthesis of sulfonamides and β-arylsulfonyl enamines via the selective cleavage of C-N and C-H bonds through the iodine-catalyzed oxidation of arenesulfonyl chlorides and sodium sulfinates with tert-amines. The method uses commercially available inexpensive catalysts and oxidants, and has a wide substrate scope and operational simplicity.

Bond-Forming and -Breaking Reactions at Sulfur(IV): Sulfoxides, Sulfonium Salts, Sulfur Ylides, and Sulfinate Salts

Organosulfur compounds have long played a vital role in organic chemistry and in the development of novel chemical structures and architectures. Prominent among these organosulfur compounds are those involving a sulfur(IV) center, which have been the subject of countless investigations over more than a hundred years. In addition to a long list of textbook sulfur-based reactions, there has been a sustained interest in the chemistry of organosulfur(IV) compounds in recent years. Of particular interest within organosulfur chemistry is the ease with which the synthetic chemist can effect a wide range of transformations through either bond formation or bond cleavage at sulfur. This review aims to cover the developments of the past decade in the chemistry of organic sulfur(IV) molecules and provide insight into both the wide range of reactions which critically rely on this versatile element and the diverse scaffolds that can thereby be synthesized.

Metal-Free Catalytic Synthesis of Thiocarbamates Using Sodium Sulfinates as the Sulfur Source

A novel molecular iodine-catalyzed protocol for the construction of thiocarbamates from readily available sodium sulfinates, isocyanides, and water has been described. The present methodology offers a facile and practical route to a variety of thiocarbamates in moderate to good yields with favorable functional group tolerance by use odorless sodium sulfinates as the sulfur source. The mechanistic studies suggest the present transformation involves a radical process.

Iodine-catalyzed sulfonylation of sulfonyl hydrazides with tert-amines: a green and efficient protocol for the synthesis of sulfonamides

This study provides a direct, sustainable and eco-friendly method for the synthesis of various sulfonamides via the sulfonylation of sulfonyl hydrazides with tert-amines. The method utilizes sulfonyl hydrazides to oxidize and couple with tertiary amines through selective cleavage of C–N bonds. In this reaction, molecular iodine was used as the catalyst and t-butyl hydroperoxide was used as the oxidant.

Sustainable and eco-friendly method for the synthesis of various sulfonamides.

Molecular iodine-mediated synthesis of thiocarbamates from thiols, isocyanides and water under metal-free conditions

A simple and practical molecular iodine-mediated method for the efficient construction of thiocarbamates from isocyanides, thiols and water under metal-free and mild conditions has been developed. A variety of thiocarbamates were easily synthesized through this methodology, which has the advantages of simple operation, eco-friendly conditions, good functional group tolerance, and readily accessible raw materials.

DBN hexafluorophosphate salts as convenient sulfonylating and phosphonylating agents

Air-stable N-sulfonyl and N-phosphonyl DBN hexafluorophosphate salts have been synthesised under mild conditions as sulfonylating and phosphonylating agents. These salts are highly efficient in the sulfonylation and phosphonylation of a range of N- and O-nucleophiles to generate sulfonamides, sulfonate esters, phosphoramidates and phosphonate esters in good yields.