Sulfinate Salts Research Articles

Silver-Catalyzed Synthesis of 5-Amino-4-sulfonyl Pyrazoles from 1,2-Diaza-1,3-dienes.

A facile and dependable synthetic route for 5-amino-4-sulfonyl pyrazoles, which are substantially important in pharmaceuticals, is highly desirable. This work presents a novel cascade reaction for their efficient synthesis. The approach utilizes silver as a catalyst for C(sp2)-H sulfonylation of readily available starting materials 1,2-diaza-1,3-dienes with sulfinate salts, followed by intramolecular cascade cyclization annulation to afford the desired 5-amino-4-sulfonyl pyrazoles in good to excellent yields under mild conditions.

Sulfonylation of Pyridyl Phosphonium Salts with Sulfinate Salts in Aqueous Media for the Synthesis of 4-Pyridyl Sulfones via C-P Bond Cleavage.

A Na2S2O8-initiated sulfonylation of pyridyl phosphonium salts with sulfinate salts in aqueous media has been developed for facile access to 4-pyridyl sulfones. The reactions, which employed pyridyl phosphonium salts as efficient pyridylation agents via C-P bond activation, showed both broad substrate generality and good functional group compatibility. In addition, the scale-up synthesis and the late-stage modification of pharmaceutically active complex molecules (e.g., loratadine, bisacodyl) could also be successfully realized.

A new route for the synthesis of multi-substituted pyrrole derivatives containing a sulfonyl scaffold via the chemistry of N-sulfonylketenimine

A rapid practical new synthesis of multi-substituted pyrrole derivatives with high yields through a novel four-component reaction of sulfonyl azides, terminal alkynes, nitro compounds, and trichloroacetonitril is a remarkable achievement in organic chemistry. This strategy offers a direct and efficient route to access complex molecular structures from readily available starting materials. To expand the work, the reaction of the final product with sulfinate salt under simple conditions and room temperature, poly-substituted pyrroles with sulfone functional group are formed. The combination of available starting materials, catalytic systems, mild reaction conditions, and ease of purification procedures contributes to the attractiveness of this method for the synthesis of diverse multi-substituted pyrrole derivatives.

Electrophotocatalytic Tellurosulfonylation of Alkynes for the Synthesis of β-(Telluro)vinyl Sulfones.

Difunctionalization of alkynes has gained a lot of interest in current organic chemistry. Herein, we developed an electrophotocatalytic multicomponent cascade reaction of alkynes and indoles with sulfinic acid sodium salts using elemental tellurium as the tellurium source. Using synergistic anodic oxidation and visible-light irradiation, various β-(telluro)vinyl sulfones have been prepared. This strategy features mild reaction conditions, excellent substrate scope, readily available starting materials, and great functional group tolerance.

Synthesis of Vinyl and 1,3‐Dienyl Sulfones Enabled by Photochemical Excitation of Halogen‐Bonding Complexes

AbstractThe photochemical catalyst‐free radical‐based synthesis of vinyl and 1,3‐dienyl sulfones is disclosed. Mechanistic investigations support that the transformations rely on a visible‐light‐promoted activation of a halogen‐bonding complex, which is formed between an alkenyl (or 1,3‐dienyl) bromide and a sodium sulfinate salt. The reactions exhibit a wide functional group tolerance (compatible with heteroatoms, electron‐withdrawing and electron‐donating groups), finding application in the structural modification of biologically relevant molecules. Eventually, a continuous flow protocol was developed to upscale these transformations.

Photoinduced decatungstate-catalyzed C(sp3)-H thioetherification by sulfinate salts.

Thiols and thioesters play crucial roles in pharmaceuticals, biology, and material science as essential organosulfur compounds. Leveraging readily available and cost-effective inert alkanes through direct thioetherification holds promise for yielding high-value-added products. Herein, we present a photoinduced strategy for sulfur-containing modification of inert alkanes utilizing decatungstate as hydrogen atom transfer reagent, offering a straightforward and practical approach for synthesizing thioethers and thioesters.

Mechanochemical-assisted decarboxylative sulfonylation of α,β-unsaturated carboxylic acids with sodium sulfinate salts

Herein, we report a mechanochemical-assisted decarboxylative sulfonylation of α,β-unsaturated carboxylic acids with sodium sulfinate salts using potassium iodide as an activator under water-assisted grinding conditions.

Enantioselective sulfonylation to construct 3-sulfonylated oxindoles.

Asymmetric synthesis of 3-sulfonylated 3-substituted oxindoles through the addition of sodium sulfinate salts to 3-bromo-3-substituted oxindoles has been achieved using chiral nickel complexes of N,N'-dioxides. This method facilitates the creation of diverse chiral sulfonyl oxindoles, several of which display promising anticancer properties. Notably, the catalyst demonstrates remarkable tolerance to water, crucial for maintaining enantioselectivity. Furthermore, the utilization of topographic steric maps of the catalysts offers valuable insights into the mechanism underlying enantioselection reversal.

Light-induced β-hydroxy sulfone synthesis in DNA-encoded libraries.

We here describe a visible-light photooxidation of sulfinate salts with common alkenes to yield β-hydroxy sulfones on DNA. This process demonstrates a broad substrate compatibility and achieves conversion rates ranging from moderate to excellent. Most importantly, it presents a straightforward, efficient, and metal-free approach for synthesizing Csp3-rich DNA-encoded libraries.

Organophotocatalyzed Alkyl/Arylsulfonylation of Vinylcyclopropanes.

Allyl sulfones are an essential pharmacophore in many bioactive compounds. To combat their synthetic barrier, we report a practical, straightforward organophotocatalyzed methodology for accessing miscellaneously functionalized allyl sulfone derivatives using inexpensive and bench-stable sodium sulfinate salts under mild conditions. This photo-catalyzed radical sulfonylation provides access to a variety of allyl sulfones in good to excellent yields with high E : Z selectivity. A wide range of vinyl cyclopropanes, as well as aryl/hetero and alkyl sodium sulfinates, were tolerated and reliable in gram-scale synthesis. Later on, further functionalization of allyl sulfones was demonstrated. A plausible mechanism for radical sulfonylation is proposed from the control experiments.

House-Meinwald rearrangement of aryl-substituted epoxysulfones in hexafluoroisopropanol (HFIP)

β-Aryl-substituted α,β-epoxysulfones undergo House-Meinwald rearrangement to form α-aryl, α-sulfonyl aldehydes in high yields upon dissolution in hexafluoroisopropanol (HFIP), and in some cases, heating. These compounds are typically isolated as the corresponding alcohols following reduction with NaBH4. The β-aryl group is generally required for rearrangement and a variety of substitution patterns are tolerated. A one-pot rearrangement/reductive amination sequence transforming the phenyl-substituted epoxysulfone to the corresponding β-aminosulfone is also reported. The epoxysulfone rearrangement substrates are directly accessible via Darzens reactions of aldehydes with chloromethyl aryl sulfones, which are themselves available using one-pot transformations of sulfonyl chlorides or sulfinate salts.

Dual Copper- and Aldehyde-Catalyzed Transient C-H Sulfonylation of Benzylamines.

This study reports the first example of using a dual catalytic system with copper(II) acetate and 2-hydroxynicotinaldehyde to achieve transient C(sp2)-H sulfonylation of benzylamines with sulfinate salts via a dynamically formed imine directing group. Manganese(IV) oxide was identified as an effective oxidant and base. Computational density functional theory investigations suggest that the transient directing group lowers the energy barrier for an acetate-mediated, turnover-limiting C-H activation step and subsequent combination of the cupracycle with a RSO2 radical.

Development of a Scalable Electrophilic Amination Protocol for the Multi-kg Production of 5-Methyl-2-pyridinesulfonamide: A Regulatory Starting Material of Endothelin Receptor Antagonist Clazosentan

5-Methyl-2-pyridinesulfonamide is a regulatory starting material of endothelin receptor antagonist clazosentan. The original route to the key sulfonamide relied on the textbook conversion of the corresponding thiophenol to the intermediate sulfonyl chloride followed by its quenching with aqueous ammonia. However, this route suffered from a wide range of issues such as a low overall yield (29%), challenging aqueous workups and isolations, and the formation of a genotoxic benzyl chloride impurity. Therefore, we developed a conceptually novel production route for 5-methyl-2-pyridinesulfonamide. The new process relied on selectively oxidizing the thiophenol to the intermediate sulfinate salt followed by an electrophilic amination of the nucleophilic sulfinate sulfur-atom with hydroxylamine-O-sulfonic acid (HOSA). This oxidation/electrophilic amination sequence worked as a “one-pot” procedure by simply adding HOSA to the reaction mixture after complete oxidation of the thiophenol with 70% aq. t-BuOOH. The process was extensively optimized with regard to the oxidation step, increasing the stability of HOSA in the reaction mixture, and the final isolation of 5-methyl-2-pyridinesulfonamide. The new process was performed on a 22 kg scale, delivering the desired product as a white solid in 69% overall yield and excellent purity (>99.9% a/a).

1,2‐Arylsulfonylation of Vinyl Ethers and Esters Enabled by Dual Ni Catalysis

AbstractA dual photocatalytic sulfonylation‐arylation of electron‐rich alkenes is described. By combining sulfinate salts, (hetero)‐aryl‐bromides and 2,3‐dihydrofuran under Ru and Ni dual catalysis, over 35 examples of aryl‐sulfonylated scaffolds could be obtained in good to excellent yields, under mild reaction conditions and high diastereoselectivity.

Fluorescent labeling of RNA and DNA on the Hoogsteen edge using sulfinate chemistry.

We have devised a single pot, low-cost method to add azide groups to unmodified nucleic acids without the need for enzymes or chemically modified nucleoside triphosphates. This involves reacting an azide-containing sulfinate salt with the nucleic acid, leading to replacement of C-H bonds on the nucleobase aromatic rings with C-R, where R is the azide-containing linker derived from the original sulfinate salt. With the addition of azide functional groups, the modified nucleic acid can easily be reacted with any alkyne-labeled compound of interest, including fluorescent dyes as shown in this work. This methodology enables the fluorescent labeling of a wide variety of nucleic acids, including natively folded RNAs, under mild conditions with minimal effects upon biochemical function and ribozyme catalysis. To demonstrate this, we show that a pair of labeled complementary ssDNA oligonucleotides (oligos) can hybridize to form dsDNA, even when labeled with multiple fluorophores per oligo. In addition, we also demonstrate that two different group II introns can splice when prelabeled internally with fluorophores, using our method. Broadly, this demonstrates that sulfinate modification of RNA is compatible with ribozyme function and Watson-Crick pairing, while preserving the labile backbone.

Catalytic Photoinduced Intramolecular Decarboxylative and Desulfonylative sp3Allylation Enabled by Sulfinate Salts.

Herein, we describe a catalytic intramolecular decarboxylative/desulfonylative sp3 allylation triggered by sulfinate salts under light irradiation. The reaction is likely enabled by a non-classical, radical-polar crossover reaction, allowing to rapidly and reliably access valuable allyl architectures from readily accessible precursors. The protocol is characterized by its operational simplicity and scalability, employing abundant, commercially available catalysts.

Catalytic Photoinduced Intramolecular Decarboxylative and Desulfonylative sp3 Allylation Enabled by Sulfinate Salts

AbstractHerein, we describe a catalytic intramolecular decarboxylative/desulfonylative sp3 allylation triggered by sulfinate salts under light irradiation. The reaction is likely enabled by a non‐classical, radical‐polar crossover mechanism, allowing rapid and reliable access to valuable allyl architectures from readily accessible precursors. The protocol is characterized by its operational simplicity and scalability, employing abundant, commercially available catalysts.

Ring-Opening 1,3-Sulfonylation-Fluorination of Donor-Acceptor Cyclopropanes: Three-Component Access to γ-Fluorosulfones.

A general method for 1,3-bisfunctionalization of donor-acceptor (D-A) cyclopropanes using sulfinate salts and electrophilic fluorination reagents is described. Utilizing Lewis acid catalysis, nucleophilic ring-opening by the sulfinate anion followed by trapping of electrophilic fluorine by the anionic intermediate leads to the formation of γ-fluorosulfones. To the best of our knowledge, this is the first direct one-step synthesis of sulfones fluorinated in the γ-position from a carbon backbone. A mechanistic proposal is presented based on experimental evidence.

Amino Acid Sulfinate Salts as Alkyl Radical Precursors

A general approach to the synthesis of amino acid sulfinate salts from commercially available α-chiral hydroxylated amino acids is reported. These reagents are shown to be valuable precursors to alkyl radicals under mild photochemical oxidation conditions. The photochemically generated amino acid radicals engage readily with alkyl and aryl disulfide radical traps to afford a diverse suite of modified amino acids.

Cover Picture

An inversion of the conventional reactivity of OTf and Cl is similar to the hare and the tortoise in a racing game. With tBuPhSelectPhos in a palladium‐catalyzed desulfinative cross‐coupling of polyhalogenated aryl triflates with aryl sulfinate salts, C—Cl group is more preferable over C—OTf and shows a reactivity order of C—Br > C—Cl > C—OTf. More details are discussed in the article by So et al. on page 909—914.image