A new and convenient synthetic way to 2-substituted thieno[2,3-b]indoles

Abstract

SummaryA short and robust approach for the synthesis of 2-(hetero)aryl substituted thieno[2,3-b]indoles from easily available 1-alkylisatins and acetylated (hetero)arenes has been advanced. The two-step procedure includes the “aldol-crotonic” type of condensation of the starting materials, followed by treatment of the intermediate 3-(2-oxo-2-(hetero)arylethylidene)indolin-2-ones with Lawesson’s reagent. The latter process involves two sequential reactions, namely reduction of the C=C ethylidene double bond of the intermediate indolin-2-ones followed by the Paal–Knorr cyclization, thus affording tricyclic thieno[2,3-b]indoles.

Three‐Component Thieno[2,3‐b]indole Synthesis from Indoles, Alkenes or Alkynes and Sulfur Powder under Metal‐Free Conditions

“…There are few methods for the synthesis of thieno[2,3‐ b ]indoles in the literature, including deoxygenative cyclization of 2‐(2‐nitrophenyl)thiophene in refluxing triethyl phosphate, oxidative cyclization of indolin‐2‐thiones, radical or palladium‐catalyzed cyclization of 3‐(2‐bromoindol‐3yl)acrylonitriles, condensation of 3‐unsubstituted indolin‐2‐thione, intramolecular NH/CH‐coupling in benzo[ b ]thiophenes, condensation of 1‐alkylisatins and acetylated (hetero)arenes, AlCl 3 ‐catalyzed recyclization of 2‐(2‐nitrocyabatophenyl)furanes, and among others . However, all the aforementioned synthetic methods use functionalized indoles, furans, isatins and thiophenes, which require several steps to be prepared.…”

“…[3] The substituted thieno [2,3-b]indoles are useful for the treatment of epilepsy, neurological diseases such as Parkinson's disease and pain. [5] There are few methods for the synthesis of thieno [2,3-b]indoles in the literature, including deoxygenative cyclization of 2-(2-nitrophenyl)thiophene in refluxing triethyl phosphate, [6] oxidative cyclization of indolin-2-thiones, [7] radical or palladium-catalyzed cyc-lization of 3-(2-bromoindol-3yl)acrylonitriles, [8] condensation of 3-unsubstituted indolin-2-thione, [9] intramolecular NH/CH-coupling in benzo[b]thiophenes, [10] condensation of 1-alkylisatins and acetylated (hetero) arenes, [11] AlCl 3 -catalyzed recyclization of 2-(2-nitrocyabatophenyl)furanes, [12] and among others. [5] There are few methods for the synthesis of thieno [2,3-b]indoles in the literature, including deoxygenative cyclization of 2-(2-nitrophenyl)thiophene in refluxing triethyl phosphate, [6] oxidative cyclization of indolin-2-thiones, [7] radical or palladium-catalyzed cyc-lization of 3-(2-bromoindol-3yl)acrylonitriles, [8] condensation of 3-unsubstituted indolin-2-thione, [9] intramolecular NH/CH-coupling in benzo[b]thiophenes, [10] condensation of 1-alkylisatins and acetylated (hetero) arenes, [11] AlCl 3 -catalyzed recyclization of 2-(2-nitrocyabatophenyl)furanes, [12] and among others.…”

One-pot multicomponent synthesis of thieno[2,3-b]indoles catalyzed by a magnetic nanoparticle-supported [Urea]4[ZnCl2] deep eutectic solvent

“…Traditionally, thieno [2,3-b] indoles are synthesized using functionalized 2-alkynylphenylisothiocyanates, 1-alkylisatins, and indole-2-thiones as starting materials, and require several steps to afford the desired products (Scheme 1). [8][9][10] Although these classical approaches have been extensively used, there is ongoing research for new methods that have simpler work-ups, are atom-economical with good to excellent yields, use recyclable catalysts and use readily inexpensive starting materials. To date, only two reports have described the synthesis of thieno [2,3-b]indoles via a one-pot multicomponent reaction which provides a greener approach than the classical methods.…”

I 2 -catalyzed one-pot synthesis of benzofuro/thieno[2,3- b ]pyrrole motifs

“…5 It should be noted that pyrrole ring systems have been attracted researchers to design light emitting diodes and transistors. 11 Considering these impressive biological and chemophysical properties of pyrrole derivatives and their significant role in organic synthesis, the development of versatile, convenient, and efficient methods for the synthesis of these core moieties has been attracted considerable attention from both the academic and industrial communities. The classical routes to pyrrole-fused heterocyclic system proceeded from the (i) reaction of O-phenyl-conjugated oxime ether with an alkyl radical, 12 (ii) Baldwin's cyclization of 3-substituted pyrrolidinediones, 13 (iii) thermolysis of the methyl 2-azido-3-(3-furyl)propenoate, 14 (iv) reaction between 1,2-diaza-1,3-butadienes and diethyl or dimethyl acetylsuccinate, 15 (v) Gewald reaction of 1,3-dicarbonyl compound, alkyl or aryl isothiocyanates via ketene N,S-acetal intermediate, followed by a Dieckmann type cyclization, 16 (vi) reductive cyclization of 3-(2-nitrophenyl)thiophenes via nitrene intermediates, 17 (vii) radical or palladium catalyzed cyclization of 3-(2-bromoindol-3-yl)acrylonitriles.…”