Copper-Catalyzed Tandem Cyclization/Chalcogenation with Elemental S8/Se: Concise Synthesis of 3-(β-Hydroxychalcogen)benzofurans

A novel copper-catalyzed cyclization/chalcogenation of o-alkynylphenols with epoxides and elemental S8/Se was developed for the synthesis of a 3-chalcogen-benzofuran architecture in a domino process with no intermediate isolation or purification. Various sensitive functional groups were compatible at room temperature and furnished chalcogenation derivatives in moderate to good yields.

Photoinduced Radical Cyclization of 2-Alkynylthioanisoles with Disulfides without an External Photocatalyst

An efficient strategy for the synthesis of 3-arylthiobenzo[b]thiophenes via a photodriven radical cyclization of 2-alkynylthioanisoles with disulfide was developed. The reaction proceeded smoothly under visible-light irradiation without any external photocatalyst and generated the desired products in high yields with good functional group tolerance.

Access to Sulfur-Containing Bisheterocycles through Base-Promoted Consecutive Tandem Cyclization/Sulfenylation with Elemental Sulfur

A convenient and efficient tandem cyclization/sulfenylation of o-alkynyl-phenols/-anilines/enaminones for the synthesis of diverse sulfur-containing bisheterocycles has been developed using stable, odorless, and easy-to-handle elemental S₈ as a building block under green chemistry conditions. Notably, a one-step simple base-mediated organic transformation affords a benzofuran (indole or chromone) ring and two C-S bonds. Attractive features of this methodology include the absence of a metal catalyst, mild conditions, good functional group tolerance, and valuable product structures.

Oxidant- and Catalyst-Free Synthesis of Sulfonated Benzothiophenes via Electrooxidative Tandem Cyclization

A green and practical electrochemical method for the synthesis of C-3-sulfonated benzothiophenes from 2-alkynylthioanisoles and sodium sulfinates was developed under oxidant- and catalyst-free conditions. Moderate to good yields of sulfonated benzothiophenes bearing important and useful functional groups have been achieved at a constant current. Preliminary mechanistic studies indicated a tandem radical addition-cyclization pathway. Moreover, the protocol is easy to scale up and exhibits good reaction efficiency.

Cascade Radical Annulation of 2-Alkynylthio(seleno)anisoles with Acetone or Acetonitrile: Synthesis of 3-Acetomethyl- or Cyanomethyl-Substituted Benzothio(seleno)phenes

An efficient method for the direct preparation of 3-aceto(cyano)methyl-substituted benzothio(seleno)phenes has been achieved through C(sp³)-H bond activation of easily available acetone or acetonitrile and cascade radical cyclization reaction. In this cascade radical cyclization reaction, C(sp²)-C(sp³) and C(sp²)-S bonds, as well as benzenethio(seleno)phene skeletons, can be built along with the cleavage of the C(sp³)-S bond, demonstrating the high step-economics and efficiency of this approach.

Recent Progress in the Synthesis of Benzo[b]thiophene

:

Due to such a wide range of applicability, the synthesis of benzo[b]thiophene derivatives has attracted intensive research. Numerous mild and efficient approaches for the synthesis of benzo[b]thiophenes have been developed over the years. Different catalysts and substrates have been applied for benzo[b]thiophene synthesis. This review will focus on the studies in the construction of benzo[b]thiophene skeleton, which date back from 2012.

Trifluoromethylthiolative 1,2-difunctionalization of alkenes with diselenides and AgSCF3

An efficient regioselective difunctionalization of alkenes via trifluoromethylthiolation has been accomplished employing diaryl diselenide and AgSCF₃ in the presence of BF₃·OEt₂.

BiCl3-Mediated direct functionalization of unsaturated C–C bonds with an electrophilic SCF2PO(OEt)2 reagent

A general access to challenging and unprecedented C(sp)–, C(sp²)– and C(sp³)–SCF₂PO(OEt)₂ bonds via a BiCl₃ mediated transformation.

Late stage trifluoromethylthiolation strategies for organic compounds

Substitution by the CF3S group allows for an increase in lipophilicity and electron-withdrawing properties along with an improvement in the bioavailability of medicinal targets; consequently, the late stage introduction of CF3S moieties into medicinal scaffolds is a sought-after strategy in synthetic organic chemistry. Different newly-developed electrophilic and nucleophilic reagents are used to effect the trifluoromethylthiolation of (hetero)aromatic compounds, aliphatic compounds (alkyl, alkenyl, alkynyl substrates), the trifluoromethylthiolation at the α- and β-carbonyl positions, and heteroatoms (N- and S-). Such reactions can involve homolytic substitutions, or functional-group substitutions (ipso). Addition reactions of electrophilic reagents to double and triple bonds followed by ring-cyclizations will be shown to yield relevant CF3S-substituted heteroaromatic compounds with relevant pharmacological action.

Bismuth(III)-Promoted Trifluoromethylthiolation of Pyrazolin-5-ones with Trifluoromethanesulfenamide

An efficient and facile method for the synthesis of trifluoromethylthiolated 5-hydroxy-1H-pyrazole derivatives by reaction of pyrazolin-5-ones with trifluoromethanesulfenamide (PhNHSCF₃) in the presence of BiCl₃ was developed.

Tandem trifluoromethylthiolation/aryl migration of aryl alkynoates to trifluoromethylthiolated alkenes

The oxidative trifluoromethylthiolation of aryl alkynoates with AgSCF₃ provided a new access to trifluoromethylthiolated alkenes.

AgSCF3-mediated trifluoromethylthiolation of α,α-diaryl allylic alcohols via radical neophyl rearrangement

A novel example of AgSCF₃-mediated oxidative radical trifluoromethylthiolation of α,α-diaryl allylic alcohols is presented, producing various α-aryl-β-trifluoromethylthiolated carbonyl ketones via radical neophyl rearrangement under mild conditions.

Enantioselective Trifluoromethylthiolating Lactonization Catalyzed by an Indane-Based Chiral Sulfide

Enantioselective trifluoromethylthiolation, especially of alkenes, is a challenging task. In this work, we have developed an efficient approach for enantioselective trifluoromethylthiolating lactonization by designing an indane-based bifunctional chiral sulfide catalyst and a shelf-stable electrophilic SCF3 reagent. The desired products were formed with diastereoselectivities of >99:1 and good to excellent enantioselectivities. The transformation represents the first enantioselective trifluoromethylthiolation of alkenes and the first enantioselective trifluoromethylthiolation that is enabled by a catalyst with a Lewis basic sulfur center.

Recent developments in synthetic methods for benzo[b]heteroles

Benzo[b]heteroles containing heteroatoms other than nitrogen and oxygen have received considerable attention for their potential applications in materials science. This poses an increasing demand for efficient, selective, and broad-scope methods for their synthesis. This review article summarizes the recent developments in synthetic methods and approaches to access representative members of the benzoheterole family.

Quantitative Scale for the Trifluoromethylthio Cation-Donating Ability of Electrophilic Trifluoromethylthiolating Reagents

A new parameter, trifluoromethylthio cation-donating ability (Tt(+)DA), is introduced as a quantitative descriptor for the propensity of electrophilic trifluoromethylthiolating reagents to transfer a CF3S moiety in organic synthesis. The first Tt(+)DA scale of popular reagents has been established through DFT calculations. Excellent correlation has been identified between the Tt(+)DAs of N-SCF3-type reagents and the pKa of the corresponding acids, offering a powerful avenue for the rational design of novel reagents.

Efficient catalytic α-trifluoromethylthiolation of aldehydes

An efficient organocatalytic method for α-trifluoromethylthiolation of aldehydes has been developed.

Diaryl Selenide Catalyzed Vicinal Trifluoromethylthioamination of Alkenes

An efficient approach to vicinal trifluoromethylthioamination of alkenes with a broad substrate scope catalyzed by electron-rich diaryl selenide has been developed. This intermolecular amination strategy was successfully applied to SCF3-esterification of alkenes using weak acids as nucleophiles.

Electrophilic trifluoromethylthiolation of thiols with trifluoromethanesulfenamide

Efficient and highly selective, metal-free, acid promoted synthesis of trifluoromethyl disulfides from thiols and PhNHSCF₃ is described.

Mild electrophilic trifluoromethylthiolation of ketones with trifluoromethanesulfanamide

A straightforward and convenient approach for trifluoromethylthiolation of various acyclic and cyclic ketones with PhNHSCF₃ is described. The reaction proceeds smoothly in the presence of acetyl chloride at room temperature and affords α-trifluoromethylthiolated ketones in fair to good yields.

Regioselective access to CF3S-substituted dihydrofurans from homopropargylic alcohols with trifluoromethanesulfenamide

A facile access to 4-((trifluoromethyl)thio)-2,3-dihydrofurans from unprotected homopropargylic alcohols in high regioselectivity is reported.

Acid-promoted direct electrophilic trifluoromethylthiolation of phenols

A highly selective and effective, acid-promoted, electrophilic trifluoromethylthiolation of phenols is described.

Direct radical trifluoromethylthiolation and thiocyanation of aryl alkynoate esters: mild and facile synthesis of 3-trifluoromethylthiolated and 3-thiocyanated coumarins

A facile oxidative radical cyclization of aryl alkynoate esters for the synthesis of 3-trifluoromethylthiolated and 3-thiocyanated coumarins is developed.