Reaction of arynes with sulfoxides

On the Risk of 18F-Regioisomer Formation in the Copper-Free Radiofluorination of Aryliodonium Precursors

Aryliodonium precursors are widely applied for copper-free labeling of positron emission tomography (PET) tracers with fluorine-18. We assessed 18F-fluoroarene regioisomer formation in examples of these labeling methods. Aryliodonium ylides derived from Meldrum's acid bearing para electron-donating groups react with [18F]fluoride in acetonitrile to produce regioisomeric 18F-fluoroarenes via a competing aryne pathway. Regioisomer formation is decreased or absent in DMF. Analytically checking for the absence of the 18F-regioisomer from any particular PET tracer radiosynthesis using these or similar methods is recommended.

Two Cascade Processes Initiated by the Insertion of Benzyne into the Se═O Bond

Two sets of cascade processes have been realized, both of which were initiated with a benzyne insertion into the Se═O bond. The key factors to differentiate these processes are based on the structures of diaryl selenium oxides and reaction conditions. When diaryl selenium oxides containing an ortho weak σ-electron-withdrawing group were used, triarylselenonium salts were obtained at room temperature, while ortho-(aryloxy)phenyl phenyl selanes could be produced from diaryl selenium oxides at 100 °C.

Diverse Synthesis of Triarylselenonium Salts and o-(Alkoxy)aryl Aryl Selanes via Insertion of Benzyne into the Se═O Bond

An insertion of benzyne into the Se═O bond has been realized. In this reaction, two types of compounds containing selenium could be synthesized from different substrates. When diaryl selenium oxides were used, triarylselenonium salts were furnished, while o-(alkoxy)phenyl phenyl selanes could be produced from aryl alkyl selenium oxides.

Bromine-Promoted One-Pot Furo[b]annulation and α-C(sp2)-Thiomethylation Cascade of (E)-3-Styrylquinoxalin-2(1H)-ones with Dimethyl Sulfoxide

A new process has been developed for the bromine-promoted sequential (sp²)C = (sp²)C bond functionalization of (E)-3-styrylquinoxalin-2(1H)-ones and furo[b]annulation via the 5-exo-cyclization in dimethyl sulfoxide (DMSO). The reaction represents a novel strategy for the synthesis of 2-aryl-3-(methylthio)furo[2,3-b]quinoxalines and involves 3-(1,2-dibromo-2-arylethyl)quinoxalin-2(1H)-ones and 2-arylfuro[2,3-b]quinoxalines as key intermediates. Furthermore, DMSO was converted to dimethyl sulfide in situ, which served as the methylthiolation reagent in the reaction. This protocol constitutes an efficient and convenient method for the annulation and methylthiolation of (E)-3-styrylquinoxalin-2(1H)-ones bearing a wide range of functional groups in high yields at room temperature.

Application of DMSO as a methylthiolating reagent in organic synthesis

In the past decades, DMSO has been widely used not only as a common solvent but also as an environmentally benign oxidant in various organic transformations. Most strikingly, DMSO can be used as a sulfur source to construct methylthiolated building blocks of potential biologically active molecules, which is a remarkable achievement in the field of organic sulfur chemistry. The purpose of this review article is to summarize and discuss the main developments in the application of DMSO as a methylthiolating reagent to introduce the -SMe functionality in organic synthesis.

Electrochemical Sulfoxidation of Thiols and Alkyl Halides

Sulfoxides are actively engaged as versatile synthetic building blocks, chiral ligands, bioactive molecules, and function materials. However, their oxidative syntheses from thioethers are inevitably impeded by overoxidation, excess oxidants, and the tedious preparation of thioethers. To address these shortcomings, we report herein a highly selective electrochemical sulfoxidation reaction featuring the use of simple starting materials, i.e., thiols and alkyl halides, in a single operation.

Recent Advances in Construction of C(sp2)–O Bonds via Aryne Participated Multicomponent Coupling Reactions

Aryne chemistry is a powerful synthetic technique that forms new bonds to aromatic rings. The recent resurgence of aryne-based multicomponent coupling strategies has led to an influx of methodologies for the mild synthesis of arene derivatives. In particular, these innovative discoveries broaden and streamline approaches toward phenol ether motifs, which are a prevalent structural component across a broad range of chemistry related research fields. Herein, this review aims to provide a comprehensive overview of the recent progress in the construction of C(sp2)–O bonds via aryne-induced multicomponent reactions. Special attention has been paid to reaction design and mechanistic pathways.

1 Introduction

2 Insertion-Based MCRs

3 Nucleophilic-Addition-Based MCRs

4 Cycloaddition-Based MCRs

5 Summary

One-pot synthesis of 3-substituted-3-hydroxyindolin-2-ones: three component coupling of N-protected isatin, aryne precursor and 1,3-cyclodione under metal-free conditions

A transition-metal free synthetic strategy for the direct synthesis of 3-substituted-3-hydroxy-indolin-2-ones via three component coupling of N-protected isatin, aryne precursor, and 1,3-cyclodione.

MnSO4-Promoted S-O Bond Cleavage to Synthesize Functionalized Sulfonium Ylides from Activated Alkynes and Sulfoxides

A variety of functionalized sulfonium ylides were prepared in good yields through MnSO4-promoted S-O bond cleavage from activated alkynes and sulfoxides. Experimental results showed that MnSO4-catalyst played important roles to...

Reactions of Sulfoxides with Benzynes

Sulfoxides are important organic synthons that have been used in a variety of transformations. In this account, we focus on advances in the reaction of sulfoxides with benzynes, which can be divided into two types: benzyne ortho-difunctionalization and benzyne multifunctionalization.

1 Introduction

2 Benzyne ortho-Difunctionalization

3 Benzyne Multifunctionalization

4 Conclusion

Access to diverse organosulfur compounds via arynes: a comprehensive review on Kobayashi's aryne precursor

Arynes are highly reactive transient intermediates having enormous applications in organic synthesis. In the last three decades aryne chemistry has shown incredible developments in carbon-carbon and carbon-heteroatom bond formation reactions. After the discovery of Kobayashi's protocol for the generation of aryne intermediates in a mild way, this field of chemistry witnessed rapid growth in synthetic organic chemistry. One aspect of development in this field involves C-S bond formation under mild conditions which has a tremendous scope for the synthesis of various important organosulfur building blocks.

Three-Component, Diastereoselective [6 + 3] Annulation of Tropone, Imino Esters, and Arynes

A transition-metal-free, three-component, and diastereoselective [6 + 3] annulation reaction employing tropone, imino esters, and arynes allowing the synthesis of bridged azabicyclo[4.3.1]decadienes is demonstrated. The key nitrogen ylides for the [6 + 3] annulation were generated by the addition of imino esters to the arynes followed by a proton transfer. The nitrogen ylides undergo a regioselective addition to tropone to furnish the desired products in moderate to good yields with good functional group tolerance under mild conditions.

Sulfurane [S(IV)]-Mediated Fusion of Benzynes Leads to Helical Dibenzofurans

Here we disclose a sulfurane-mediated method for the formation of dimeric dibenzofuran helicenes via the reaction between diaryl sulfoxides and hexadehydro-Diels-Alder (HDDA) derived benzynes. A variety of S-shaped and U-shaped helicenes were formed under thermal conditions. Both experimental and DFT studies support a sulfur(IV)-based coupling (aka ligand coupling) mechanism involving tetracarbo-ligated S(IV) intermediates undergoing reductive elimination to afford the helicene products. This process involves the de novo generation of five new rings in a single operation and constitutes a new method for the construction of topologically interesting, polycyclic aromatic compounds.

Unexpected Substituent Effects in Spiro-Compound Formation: Steering N-Aryl Propynamides and DMSO toward Site-Specific Sulfination in Quinolin-2-ones or Spiro[4,5]trienones

A highly substituent-dependent rearrangement allows for the novel and SOCl₂-induced divergent synthesis of 3-methylthioquinolin-2-ones and 3-methylthiospiro[4.5]trienones through intramolecular electrophilic cyclization of N-aryl propyamides. DMSO acts as both solvent and sulfur source, and use of DMSO-h₆/d₆ enables the incorporation of SCH₃ or SCD₃ moieties to the 3-position of the heterocyclic framework. Different para-substituents trigger divergent reaction pathways leading to the formation of quinolin-2-ones for mild substituents and spiro[4,5]trienones for both electron-withdrawing and -donating substituents, respectively. On the basis of both computational and experimental results, a new mechanism has been put forward that accounts for the exclusive spirolization/defluorination process and the surprising substituent effects.

o-Quinone Methides and o-Quinone Sulfides via Arynes: Synthesis of Ortho-Disubstituted Arenes and Heterocycles

In recent decades, o-quinone methides and o-quinone sulfides have been extensively highlighted as reactive intermediates for the synthesis of diversely functionalized ortho-disubstituted arenes and heterocycles. Additionally, ortho-disubstituted arenes offer a constructive path for the synthesis of fused carbocycles, heterocycles, natural products, and drug candidates. In the lieu of that, this Synopsis highlights a comprehensive overview on the potential applications of in situ generated o-quinone methides and o-quinone sulfides for one-pot synthesis of ortho-disubstituted arenes and heterocycles via arynes.

An efficient synthesis of 4-phenoxy-quinazoline, 2-phenoxy-quinoxaline, and 2-phenoxy-pyridine derivatives using aryne chemistry

Herein we report the mild and efficient synthesis of 4-phenoxyquinazoline, 2-phenoxyquinoxaline, and 2-phenoxypyridine derivatives from the starting materials viz. quinazolin-4(3H)-one, quinoxalin-2(1H)-one, and pyridin-2(1H)-one and aryne generated in situ from 2-(trimethylsilyl)phenyl trifluoromethanesulfonate and cesium fluoride. This synthetic methodology gives a new environmentally benign way for the preparation of several unnatural series of 4-phenoxyquinazoline, 2-phenoxyquinoxaline and 2-phenoxypyridine compounds with high yields and broad substrate scope.

Efficient synthesis of 4-phenoxyquinazoline, 2-phenoxyquinoxaline, 2-phenoxypyridine derivatives were generated of aryne from 2-(trimethylsilyl)phenyltrifluoromethanesulfonate with cesium fluoride.

Rapid Synthesis of Zwitterionic Phosphonium Benzoates by a Three-Component Coupling Involving Phosphines, Arynes and CO2

A mild and easy to perform multicomponent coupling involving phosphines, arynes generated from 2-(trimethylsilyl)aryl triflates, and CO₂ allowing the transition-metal-free synthesis of zwitterionic phosphonium benzoates has been developed. The reaction proceeds via the generation of 1 : 1 zwitterionic intermediates from phosphines and arynes followed by the interception with CO₂ to deliver the carboxylates in moderate to good yields instead of the anticipated benzooxaphosphol-3(1H)-ones.

Macrocyclization of 3-triflyloxybenzynes with tetrahydrofuran via an anionic thia-Fries rearrangement

A novel and uncommon macrocyclization reaction between 3-triflyloxybenzynes and tetrahydrofuran has been developed for the first time, providing a direct method for the synthesis of a range of functionalized 19-membered polyether macrocycles in moderate to good yields. The process was proposed to proceed through an anionic thia-Fris rearrangement under transition metal-free conditions, leading to the formation of four new C-O bonds and one new C-S bond in a single step.

C–O/C–S difunctionalized benzene derivatives via multicomponent coupling of tetraynes

C–O/C–S difunctionalization of fused highly substituted benzene derivatives was conducted via the multicomponent coupling reaction of tetraynes, sulfoxides, and cyclopropenones.

Direct synthesis of ortho-methylthio allyl and vinyl ethers via three component reaction of aryne, activated alkene and DMSO

A transition-metal free synthetic strategy for the direct synthesis of ortho-methylthio allyl and vinyl ethers via cascade three-component coupling of aryne, activated alkene and DMSO.

Synthesis of 6-substituted indoloquinazolinones from arynes and 2-acyl-4-quinazolinones: a transition-metal free C–N and C–C bond formation strategy

A versatile transition-metal free synthetic strategy has been developed for the direct synthesis of 6-substituted indoloquinazolinones from 2-acyl-4-quinazolinones and aryne precursors. This cascade strategy proceeds via successive C–N and C–C bond formation in a single reaction vessel.

Acid-catalyzed synthesis of condensed polycyclic diaryl ethers from arenols

Diaryl ethers containing condensed polycyclic aryl groups were synthesized from arenols in the presence of a catalytic amount of p-chlorobenzenesulfonic acid. Symmetrical binaphthyl, biphenanthryl, and bipyrenyl ethers were obtained in high yields. Unsymmetrical derivatives were also synthesized from 9-phenanthrol and arenols, using combinations of reactive and unreactive substrates.

Sulfur-Mediated Allylic C-H Arylation, Epoxidation, and Aziridination

Transition-metal-free, sulfur-mediated allylic C-H arylation, epoxidation, and aziridination were realized through one-pot procedures. The reaction design involved initial addition between olefins and triflic anhydride activated sulfoxides, followed by subsequent reactions of the allylic sulfur ylides generated under basic conditions with arylboronic acids, aldehydes, or aldimines, to give allylic arylation, epoxidation, or aziridination products, respectively.

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.

The aryne Sommelet–Hauser rearrangement

An aryne induced transition-metal-free and mild Sommelet–Hauser rearrangement of tertiary benzylamines for the synthesis of α-aryl amino acid derivatives in moderate to good yields and with broad substrate scope is presented.

A cascade process for the synthesis of ortho-formyl allyl aryl ethers and 2H-chromen-2-ol derivatives from arynes via trapping of o-quinone methide with an activated alkene

A transition-metal free synthetic strategy for the direct synthesis of ortho-formyl substituted allyl aryl ethers and 2H-chromen-2-ol derivatives via a cascade three-component coupling of arynes, activated alkene and N,N-dimethylformamide.

Direct bromocarboxylation of arynes using allyl bromides and carbon dioxide

An unprecedented multicomponent reaction involving arynes, allyl bromides, and CO₂ has been developed to construct various allyl o-bromobenzoate scaffolds.

Selective S-arylation of 2-oxazolidinethiones and selective N-arylation of 2-benzoxazolinones/2-benzimidazolinones

There exist three possible patterns for the reaction of cyclic 2-oxazolidinethione and 2-benzoxazolidinethione with arynes, namely (a) S-arylation, (b) N-arylation, and (c) aryne insertion into the thiocarbonyl group (C[double bond, length as m-dash]S). Our studies demonstrate that S-arylation wins out affording S-aryl dihydrooxazoles. In contrast, for related reactions of cyclic 2-benzoxazolinone and 2-benzimidazolinone with arynes, it is found that N-arylation outcompetes O-arylation and aryne insertion into the C[double bond, length as m-dash]O group to give N-aryl 2-benzoxazolinones and N-aryl 2-benzimidazolinones.

Unmasking Dipole Character of Acyl Ketene Dithioacetals via a Cascade Reaction with Arynes: Synthesis of Benzo[b]thiophenes

An unusual strategy toward novel substituted benzo[b]thiophenes has been developed. The generation of arynes in the presence of acyl ketene dithioacetals resulted in a cascade reaction involving [3 + 2] cycloaddition, and a dealkylative arylation of a thioether moiety to afford 2,3-disubstuted benzo[b]thiophenes. This route represents an expeditious approach to benzothiophenes that employs acyl ketene dithioacetals as dipoles.

Application of Sulfur Ylides in 1,2-Difunctionalization of Arynes via Insertion into a C-S σ-Bond

A novel reactivity of sulfur ylides has been demonstrated in a transition-metal-free protocol to access ortho-substituted thioanisole derivatives by insertion of arynes into a C-S σ-bond in moderate to good yields. The reaction involves the formation of C-C and C-S bonds and consecutive breaking of two C-S bonds under operationally mild reaction conditions.

Highly mono-selective ortho-methylthiolation of benzamides via cobalt-catalyzed sp2 C–H activation

A highly mono-selective ortho-methylthiolation of benzamides was achieved via Co-catalyzed coupling of benzamides with DMSO.

Recent advances in molecular rearrangements involving aryne intermediates

A concise account on the recent developments in molecular rearrangements proceeding via the aryne intermediate is presented thereby shedding light on the synthetic potential of this versatile intermediate.

Synthesis of Diverse o-Arylthio-Substituted Diaryl Ethers by Direct Oxythiolation of Arynes with Diaryl Sulfoxides Involving Migratory O-Arylation

A diverse range of o-arylthio-substituted diaryl ethers has been synthesized by direct oxythiolation of arynes with diaryl sulfoxides that involves the formation of the C-O and C-S bonds followed by migratory O-arylation.