Construction of Benzothiophene or Benzothiopheno[2,3-e]azepinedione Derivatives via Three-Component Domino or One-Pot Sequences

Switchable C2/C3 positional selectivity of thioisatins in a three-component domino reaction: combined computational and experimental studies

The nucleophile-induced domino reaction is a featured reactivity mode of thioisatin, but the C2/C3 positional selectivity towards a nucleophile has not been understood in-depth. In this work, a domino reaction of thioisatin with bromoacetophenone and tryptamine hydrochloride to produce a benzothiophene-fused eight-membered N-heterocycle was described, showing that the Brønsted acid-base form of the amine partner was crucial for the selectivity, because using tryptamine instead of tryptamine hydrochloride gave a different product. Control experiments and density functional calculations revealed that the domino reaction using tryptamine or tryptamine hydrochloride was triggered by a condensation reaction at the C2 or C3 position of thioisatin, respectively. A delicate balance between local electrophilicity and polarization effect may be responsible for the observed selectivity.

Sustainable access to benzothiophene derivatives bearing a trifluoromethyl group via a three-component domino reaction in water

A catalyst-free three-component domino reaction was developed for the synthesis of benzothiophene fused pyrrolidones bearing a CF3 group for the first time. The notable advantages of this strategy over the existing methods include the use of water as a solvent at room temperature, transition metal-free conditions, a broad substrate scope, and easy scale-up synthesis. More importantly, the benzothiophene derivatives have been found to show potent anticancer activities using the Cell Counting Kit-8 (CCK-8) assay.

Divergent Construction of Benzothiophene-Fused N-Heterocycles via Stereotunable Three-Component Domino Reactions

A stereotunable three-component domino strategy among thioisatin, 2-bromo-1-phenylethan-1-one, and cyclohexane-1,2-diamine under catalyst-free conditions was disclosed. A wide range of benzothiophene-fused polycycles and eight-membered N-heterocycles were synthesized by regulating the stereoconfiguration of cyclohexane-1,2-diamines. The detailed mechanism and the origin of the chemoselectivity were explored by density functional calculations. Analysis of the geometrical structures of key transition states revealed that the existence of favorable intramolecular attractions, and the steric effect governed the chemoselectivity observed.

Recent advances in cyclization reactions of isatins or thioisatins via C–N or C–S bond cleavage

This review summarizes recent developments on cyclization reactions induced by the C–N or C–S bond cleavage of isatins or thioisatins in the last 5 years, which produce fused products instead of spiro compounds.

Tunable synthesis of benzothiophene fused pyranone and thiochromen fused furan derivatives via a domino process

A K₂CO₃-promoted tunable domino reaction between thioisatins and α-bromoketones was developed for the synthesis of benzothiophene fused pyranone and thiochromen fused furan derivatives via adjusting MgSO₄.