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

A cascade deprotonation/intramolecular aldol reaction of α-carbonyl sulfonium ylides with 2-mercaptoindole-3-carbaldehydes and 2-mercaptobenzaldehydes to access thieno[2,3-b]indoles and benzothiophenes

The first catalyst-free cascade deprotonation/intramolecular aldol reaction of α-carbonyl sulfonium ylides with 2-mercaptoindole-3-carbaldehydes and 2-mercaptobenzaldehydes was developed. A series of thieno[2,3-b]indoles and benzothiophenes were smoothly obtained in high to excellent yields. The salient features of the protocol include catalyst-free conditions, an environment-friendly solvent, broad substrate scope, and large-scale synthesis.

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

In this study, we have developed the synthesis of thieno[2,3-b]indole dyes via a multicomponent reaction of cheap and available reagents such as sulfur, acetophenones, and indoles using a magnetic nanoparticle-supported [Urea]₄[ZnCl₂] deep eutectic solvent as a green catalyst. The synthesis of a series of diversely functionalized thieno[2,3-b]indole has been successfully performed in a one-pot reaction. Among a total of 25 compounds synthesized, there are 21 new compounds with full characterization such as FT-IR, ¹H and ¹³C NMR, HRMS (ESI). Due to the deep eutectic solvent coated surface of the magnetic nanoparticles, the catalyst could be recovered by an external magnet and reused in five consecutive runs without a considerable decrease in catalytic activity.

We have developed the synthesis of thieno[2,3-b]indole dyes via a multicomponent reaction of cheap and available reagents using a magnetic nanoparticle-supported [Urea]₄[ZnCl₂] deep eutectic solvent as a green catalyst.

Synthesis of Functionalized Thieno[2,3-b]indoles via One-Pot Reaction of Indoline-2-thiones with Morita-Baylis-Hillman and Rauhut-Currier Adducts of Nitroalkenes

A straightforward protocol for the synthesis of functionalized thieno[2,3-b]indoles by base-mediated [3 + 2]-annulation of indoline-2-thione with Morita-Baylis-Hillman and Rauhut-Currier adducts of nitroalkenes is described. Complete regioselectivity, broad substrate scope, and mild reaction conditions make this strategy very valuable. Moreover, the thieno[2,3-b]indoles comprising functional groups such as hydrazine and ketoalkyl moieties are amenable for further synthetic elaboration.

Autoxidation/Aldol Tandem Reaction of 2-Oxindoles with Ketones: A Green Approach for the Synthesis of 3-Hydroxy-2-Oxindoles

In the presence of tetrabutylammonium fluoride and molecular sieves (MS) 4 Å in DMF, an efficient autoxidation reaction of 2-oxindoles with ketones under air at room temperature has been developed. This approach may provide a green, practical, and metal-free protocol for a wide range of biologically important 3-hydroxy-3-(2-oxo-alkyl)-2-oxindoles.