Three‐Component Synthesis of 3‐(Arylsulfonyl)benzothiophenes Using Acetic Acid as a Quencher for Methyl Radical‐Mediated Side Reactions

Abstract

A one‐pot, three‐component synthesis of 3‐(arylsulfonyl)benzothiophenes was developed. The reaction did not require any catalysts or additives. The desired products were obtained via an intramolecular radical cyclization. Acetic acid was employed as the solvent and a quencher for side reactions involving methyl radicals. Moreover, inexpensive potassium metabisulfite was used as a sulfur dioxide surrogate. This process provides more opportunities for synthesizing benzothiophene derivatives, which are found in many bioactive compounds.

Visible-Light-Induced Intermolecular Trifluoromethyl Heteroarylation of Vinyl Ethers for the Syntheses of β-Trifluoromethyl Alkyl Thiochromones

“…Larock and co-workers reported an ICl-induced cyclization of methylthiolated alkynone to access various 3-iodochromones (Scheme a, left) . Recently, the group of Song and co-workers, Huang and co-workers, Wu and co-workers, Yu and co-workers, etc . have independently developed various radical-initiated cyclization reactions using the same substrate under different conditions, affording thiochromone containing diverse substitutes in a highly efficient manner (Scheme a, right).…”

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

“…Subsequently, some new approaches to access them employing photochemical and electrochemical processes have also been developed (Scheme b). Meanwhile, Wu et al disclosed a radical relay strategy for the generation of 3-(methylsulfonyl)-benzo­[ b ]­thiophenes through the reaction of methyl­(2-alkynylphenyl)­sulfanes with sodium metabisulfite, and Lee’s group reported a three-component synthesis of 3-(arylsulfonyl)­benzo­[ b ]­thiophenes using potassium metabisulfite as a sulfur dioxide surrogate . Moreover, some facile routes to 3-((trifluoromethyl)-thio)­benzo­[ b ]­thiophenes and 3-methylthiobenzo­[ b ]­thiophenes via intramolecular cyclization of methyl­(2-alkynylphenyl)­sulfanes have also been developed (Scheme c) .…”