Recent advances of sodium sulfinates in radical reactions

Concise Synthesis of Optically Active Cyclopropane β-Amino Acid Derivatives via Olefination of Cyclopropanone Surrogates

An expedient synthesis of cyclopropane β-amino acid derivatives is reported from readily accessible cyclopropanone surrogates. The addition of stabilized phosphorus ylides to 1-sulfonylcyclopropanols leads to the formation of highly electrophilic alkylidenecyclopropanes shown to be reactive in a telescopic aza-Michael reaction, in mild conditions. The transformation proceeds with complete diastereocontrol in favor of the trans products and is amenable to the rapid production of highly enantioenriched β-amino acid derivatives, peptidomimetics and spirocyclic analogues.

Construction of multi-functionalized carbon chains by Ni-catalyzed carbosulfonylation of butadiene

Multi-functionalized carbon chains are prevalent motifs existing in various natural products and drugs. How to construct multi-functionalized carbon chains represents a meaningful task. Herein, we developed a photo-induced stereoselective 1,4-carbosulfonylation of butadiene to construct multi-functionalized carbon chains under nickel catalysis. A wide variety of aryl iodides and sodium sulfinates could be facilely coupled with butadiene to generate difunctionalized olefin intermediates. Taking advantage of the internal CC bond, various functional groups have been efficiently incorporated to construct multi-functionalized aliphatic compounds. A scale-up reaction, an iterative reaction and late-stage modifications have been performed to further demonstrate the synthetic utility of this protocol.

Palladium-Catalyzed Decarboxylative Allylic Sulfonylation of Vinyloxazolidine-2,4-diones: Synthesis of γ-Sulfonyl-α,β-unsaturated Amides

A palladium-catalyzed decarboxylative allylic sulfonylation reaction of vinyloxazolidine-2,4-diones with inexpensive and readily available sodium sulfinates as sulfonylation reagents has been developed. Under the catalysis of Pd(PPh3)4, a wide range of γ-sulfonyl-α,β-unsaturated amides can be synthesized in good to excellent yields. The developed protocol is characterized by exclusive regioselectivity, mild reaction conditions, broad substrate scope, good functional group tolerance, and suitable for gram-scale synthesis.

Sulfinate-Promoted Defluorinative Cyclization of Polyfluoroalkyl Tetralones Enabled by Photocatalysis

A Ru-catalyzed defluorinative cyclization of polyfluoroalkyl tetralones has been developed under visible-light irradiation for the precise assembly of γ-pyrones featuring α-perfluoroalkyl and β-fluorine substituents. Selective functionalization of five C(sp3)-F bonds at three carbon sites on the perfluoroalkyl chain provides a new mode for utilizing polyfluorides as versatile synthons to access difficult-to-obtain heterocyclic scaffolds. Moreover, the sulfinate salt serves dual roles as an oxygen source for creating the carbonyl group and as a defluorinating promoter.

Synthesis of disulfides and 3-sulfenylchromones from sodium sulfinates catalyzed by TBAI

A new synthetic method for disulfides and 3-sulfenylchromones is reported. This innovative approach is based on the tetrabutylammonium iodide (TBAI)/H2SO4 reduction system using sodium sulfinate as key component, thus eliminating the need for thiols and redox reagents commonly used in traditional methods. Various disulfides and 3-sulfenylchromones were obtained in moderate to excellent yields through this methodology. Mechanistic studies indicate that thiosulfonates play an important role in the reaction process.

Reactions of alkynes with C-S bond formation: recent developments

Alkynes are important in organic synthesis. This review mainly focuses on recent advances (2013-2023) on alkynes with C-S bond formation, based on more than 30 types of sulfur reagents. The reactions of alkynes with various sulfur-containing compounds including RSSR (disulfides), RSH (thiols), S8 (elemental sulphur), alkynyl thioethers, RSCN, AgSCF3, K2S, Na2S, dithiane, RSCl, NFSI, RNCS, EtOCS2K, thiocarbamate, RSONH2, thiourea, sulfoxide, RSO2N3, CS2, RSO2NH2, RSO2NHNH2, RSO2Cl, RSO2Oar, RSO2SR', DABCO·(SO2)2, Na2S2O5, K2S2O5, RSO2H, RSO2Na and related compounds are discussed. Diverse mechanisms such as radical, electrophilic/nucleophilic addition, rearrangement, C-C bond cleavage, and CuAAC are discussed. The content is organized by substrates and reactivity patterns. We hope it will help in future research in this area.

Polarity-Matched Initiation of Radical-Polar Crossover Reactions for the Synthesis of C-Allyl Glycosides with gem-Difluoroalkene Groups

Herein, we disclose a general method for the assembly of C-allyl glycosides containing gem-difluoroalkene groups via a radical-polar crossover strategy. Central to the success of this process is the polarity matching between the benzenesulfinate radical and the glycosyl donor, which facilitates the initiation of the glycosyl radical and the subsequent formation of gem-difluoroalkene sugar derivatives. This method demonstrated good compatibility with various glycosyl donors and functional groups. Furthermore, we showcase the utility of this method in modifying amino acids, potentially paving the way for analogous modifications to peptides.

Recent trends in incorporation of CO2 into organosulfur compounds via C-S bond cleavage

Desulfurative functionalization of organosulfur compounds to form various carbon-carbon and carbon-heteroatom bonds has become established as a powerful tool in organic chemistry. In this context, desulfurative carboxylation of this class of compounds using carbon dioxide (CO2) as a sustainable and renewable source of carboxyl has recently been developed as an efficient option for the synthesis of carboxylic acid derivatives. The aim of this Focus Review is to summarize the major progress in this appealing research field with particular emphasis on the mechanistic features of the reactions. Literature has been surveyed until the end of February 2024, according to the data collected using SciFinder and Google Scholar engines.

Generation of sulfones utilizing β-sulfinyl esters as masked aryl sulfinates under redox-neutral conditions

A method for generation of SVI sulfones from β-sulfinyl esters (SIV) under transition-metal-free non-oxidative mild conditions is presented. Various sulfones have been achieved with moderate to excellent yields. The advantage of using β-sulfinyl esters as masked aryl sulfinates has also been exemplified using brominated substrates. Oxygen isotope-labeling experiments indicated that the oxygen atoms incorporated into the sulfone product come from the sulfoxide of the β-sulfinyl ester. Successive β-elimination/O-addition/sulfinate esterification/β-elimination processes are proposed for the mechanism of generating SVI from SIV.

Photoinduced Photocatalyst-Free Cascade Cyclization of Alkynes with Sodium Sulfinates for the Synthesis of Benzothiophenes and Thioflavones

The subject of this investigation is a new method for the construction of sulfonylated heterocycles which overcomes the limitations of classical approaches using a cheap feedstock sulfonylating agent, especially under photocatalyst- and metal-free conditions.

Inexpensive and bench stable diarylmethylium tetrafluoroborates as organocatalysts in the light mediated hydrosulfonylation of unactivated alkenes

In this paper, we present the synthetic potential of diarylmethylium tetrafluoroborates as catalysts for the visible light promoted hydrosulfonylation of unactivated alkenes. For the first time, these salts, which are bench stable and easily preparable on a multi-gram scale, were employed as organocatalysts. Interestingly, a catalyst loading of only 1 mol% allowed sulfone products to be efficiently obtained from good-to-excellent yields with high functional-group tolerance and scalability up to 15 mmol of alkene. The mechanistic study, both experimental and computational, presented here, revealed an alternative mechanism for the formation of the key sulfonyl radical. Indeed, the photoactive species was proved not to be the diarylcarbenium salt itself, but two intermediates, a stable S-C adduct and an ion couple, that were formed after its interaction with sodium benzenesulfinate. Upon absorbing light, the ion couple could reach an excited state with a charge-transfer character which gave the fundamental sulfonyl radical. A PCET (proton-coupled electron transfer) closes the catalytic cycle reforming the diarylcarbenium salt.

Photocatalytic Defluorinative Three-Component Reaction of α-Trifluoromethyl Alkenes, Alkenes, and Sodium Sulfinates: Synthesis of Monofluorocyclopentenes

A photocatalytic three-component reaction of α-trifluoromethyl alkenes, electron-rich alkenes, and sodium sulfinates for the synthesis of gem-difluoroalkenes in a radical/polar crossover manner was developed. Due to the strong electron-withdrawing nature of the sulfonyl group, the resultant gem-difluoroalkenes can be converted into various monofluorocyclopentenes via intramolecular base-mediated S_NV reactions in one pot.

Complementary Copper-Catalyzed and Electrochemical Aminosulfonylation of O-Homoallyl Benzimidates and N-Alkenyl Amidines with Sodium Sulfinates

A complementary copper-catalyzed and electrochemical aminosulfonylation of O-homoallyl benzimidates and N-alkenyl amidines with sodium sulfinates was developed. The terminal alkene substrate produced sulfone-containing 1,3-oxazines and tetrahydropyrimidines in the presence of Cu(OAc)₂, Ag₂CO₃, and DPP, and under similar reaction conditions, sulfonylated tetrahydro-1,3-oxazepines were prepared from 1-aryl-substituted O-homoallyl benzimidates in moderate to good yields. For certain electron-rich 1,1-diaryl-substituted alkene substrates, the corresponding tetrahydro-1,3-oxazepines could also be obtained in similar or even higher yields via a green electrochemical technique.

Photoredox Activation of Organozinc Reagents: Barbier-Type Reaction of Alkyl Halides with α-(Trifluoromethyl)styrenes

Organozinc reagents may be activated under blue light irradiation using an organic photocatalyst to generate alkyl radicals. The radicals are trapped by α-(trifluoromethyl)styrenes leading to gem-difluorinated products after elimination of fluoride. The reaction can be conveniently performed under Barbier conditions starting from organic iodides and bromides and elemental zinc.