Synthesis of sulfonamides and sulfonic esters via reaction of amines and phenols with thiols using H2O2–POCl3 system

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.

Preparation of Sulfonyl Chlorides by Oxidative Chlorination of Thiols and Disulfides using HNO3/HCl/O2 in a Flow Reactor

A continuous flow metal-free protocol for the synthesis of sulfonyl chlorides from thiols and disulfides in the presence of nitric acid, hydrochloric acid and oxygen was developed. The influence of the reaction parameters was investigated under batch and flow conditions. Online 19F NMR was successfully implemented to investigate different reaction conditions within a single experiment. The sulfonyl chlorides were isolated (mostly in 70-81 % yield) after performing a simple aqueous washing procedure. In particular, the protocol was successfully operated for >6 hours to convert diphenyl disulfide to its corresponding sulfonyl chloride, achieving a throughput of 3.7 g h-1. The environmental impact of the protocol was assessed and compared to an existing continuous flow protocol using 1,3-dichloro-5,5-dimethylhydantoin (DCH) as reagent. The process mass intensity (PMI) for the newly-developed flow protocol (15) compared favorably to the DCH flow process (20).

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.

Strategies for the direct oxidative esterification of thiols with alcohols

This review paper provides an overview of the main strategies for the oxidative esterification of thiols with alcohols. The review is divided into two major parts according to final products. The first includes the methods for the synthesis of sulfinic esters, while the second contains the procedures for the fabrication of sulfonic ester derivatives.

Direct synthesis of sulfenamides, sulfinamides, and sulfonamides from thiols and amines

Needless to say that organosulfur compounds with sulfur–nitrogen bonds have found various applications in diverse fields such as pharmaceuticals, agrochemicals, polymers, and so forth. Three major groups of such compounds are sulfenamides, sulfinamides, and sulfonamides which have been widely applied as building blocks in medical chemistry. Owing to their significant role in drug design and discovery programs, the search for and development of efficient, environmentally friendly, and economic processes for the preparation of the title compounds is of great importance in the pharmaceutical industry. Recently, oxidative coupling of thiols and amines, two readily available low-cost commodity chemicals, has emerged as a highly useful method for synthesizing structurally diverse sulfenamides, sulfinamides, and sulfonamides in a single step. Since this strategy does not require additional pre-functionalization and de-functionalization steps, it considerably streamlines synthetic routes and substantially reduces waste generation. This review will focus on recent advances and achievements in this attractive research arena.

This review provides a concise overview of the synthesis of biologically and synthetically valuable sulfenamide, sulfinamide, and sulfonamide derivatives through the direct oxidative coupling of readily available low-cost thiols and amines.

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

A practical and sustainable synthesis of arylsulfonate esters has been developed through electro-oxidation. This reaction employed the stable and readily available phenols and sodium arenesulfinates as the starting materials and took place under mild reaction conditions without additional oxidants. A wide range of arylsulfonate esters including those bearing functional groups were produced in good to excellent yields. This reaction could also be conducted at a gram scale without a decrease of reaction efficiency. Those results well demonstrated the potential synthetic value of this reaction in organic synthesis.

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.

Nanosized CdS as a Reusable Photocatalyst: The Study of Different Reaction Pathways between Tertiary Amines and Aryl Sulfonyl Chlorides through Visible-Light-Induced N-Dealkylation and C-H Activation Processes

It has been found that the final products of the reaction of sulfonyl chlorides and tertiary amines in the presence of cadmium sulfide nanoparticles under visible light irradiation are highly dependent on the applied reaction conditions. Interestingly, with the change of a reaction condition, different pathways were conducted (visible-light-induced N-dealkylation or sp³ and sp² C-H activation) that lead to different products such as secondary amines and various sulfonyl compounds. Remarkably, all of these reactions were performed under visible light irradiation and an air atmosphere without any additive or oxidant in benign solvents or under solvent-free conditions. During this study, the CdS nanoparticles as affordable, heterogeneous, and recyclable photocatalysts were designed, successfully synthesized, and fully characterized and applied for these protocols. During these studies, intermediates resulting from the oxidation of tertiary amines are trapped during the photoinduced electron transfer (PET) process. The reaction was carried out efficiently with a variety of substrates to give the corresponding products at relatively short times in good to excellent yields in parallel with the use of the visible light irradiation as a renewable energy source. Most of these processes are novel or are superior in terms of cost-effectiveness, safety, and simplicity to published reports.

One-pot aerobic oxidative sulfonamidation of aromatic thiols with ammonia by a dual-functional β-MnO2 nanocatalyst

High-surface-area β-MnO2 (β-MnO2-HS) nanoparticles could act as effective heterogeneous catalysts for the one-pot oxidative sulfonamidation of various aromatic and heteroaromatic thiols to the corresponding sulfonamides using molecular oxygen (O2) and ammonia (NH3) as respective oxygen and nitrogen sources, without the need for any additives.

Oxidative ring-opening of benzothiazole derivatives

An oxidative ring opening of benzothiazole to an acylamidobenzene sulfonate ester using alcohol solvents and magnesium monoperxoyphthalate hexahydrate has been described. Under the established conditions, the reaction produces synthetically significant yields with a variety of benzothiazole derivatives. A sulfonate ester intermediate suggests that the reaction proceeds via thiazole ring opening followed by thiol oxidation.

Antitubulin sulfonamides: The successful combination of an established drug class and a multifaceted target

Tubulin, the microtubules and their dynamic behavior are amongst the most successful antitumor, antifungal, antiparasitic, and herbicidal drug targets. Sulfonamides are exemplary drugs with applications in the clinic, in veterinary and in the agrochemical industry. This review summarizes the actual state and recent progress of both fields looking from the double point of view of the target and its drugs, with special focus onto the structural aspects. The article starts with a brief description of tubulin structure and its dynamic assembly and disassembly into microtubules and other polymers. Posttranslational modifications and the many cellular means of regulating and modulating tubulin's biology are briefly presented in the tubulin code. Next, the structurally characterized drug binding sites, their occupying drugs and the effects they induce are described, emphasizing on the structural requirements for high potency, selectivity, and low toxicity. The second part starts with a summary of the favorable and highly tunable combination of physical-chemical and biological properties that render sulfonamides a prototypical example of privileged scaffolds with representatives in many therapeutic areas. A complete description of tubulin-binding sulfonamides is provided, covering the different species and drug sites. Some of the antimitotic sulfonamides have met with very successful applications and others less so, thus illustrating the advances, limitations, and future perspectives of the field. All of them combine in a mechanism of action and a clinical outcome that conform efficient drugs.

Metal-free I2O5-mediated direct construction of sulfonamides from thiols and amines

A simple and efficient metal-free I₂O₅-mediated one-pot procedure for the construction of sulfonamides from thiols and amines has been developed.

Iodine-induced synthesis of sulfonate esters from sodium sulfinates and phenols under mild conditions

A facile and highly efficient method for the synthesis of sulfonate esters mediated by iodine at room temperature has been developed, without transition metal catalysts and oxidants.

Copper-catalyzed sulfonamides formation from sodium sulfinates and amines

A new and convenient method for the construction of sulfonamides via a copper-catalyzed oxidative coupling between sodium sulfinates and amines with 1 atm O2 or DMSO as the oxidant was described. This method provides efficient and robust synthesis of functional sulfonamides in good yields and excellent chemoselectivity. And detailed mechanistic studies showed that this transformation may go through a single electron transfer (SET) pathway.

3,2-Hydroxypyridinone (3,2-HOPO) vinyl sulfonamide and acrylamide linkers: Aza-Michael addition reactions and the preparation of poly-HOPO chelators

The HOPO vinyl sulfonamide 3 and the corresponding HOPO acrylamide 10, were easily prepared by short synthetic sequences. Investigation of the aza-Michael reactions of these linkers showed that they proceed at a higher rate in solvent systems containing water. The scope and limits of the aza-Michael reactions of 3 and 10 were examined. Reagents 3 and 10 reacted cleanly with piperazine to give the corresponding adducts which were deprotected to give the di-HOPO ligands 7 and 16. Reaction of HOPO acrylamide 10 with 1,4,7-triazacyclononane gave the tris-adduct 17 which was deprotected to give the desired tris-HOPO ligand 18. Overall, the aza-Michael reactions of 3 and 10 appear to be governed not only by the solvent but also by the nature of the amine and the solubility of the reaction intermediates.