Engaging thieno[2,3‐b]indole‐2,3‐dione for the efficient synthesis of spiro[indoline‐3,4′‐thiopyrano[2,3‐b]indole] by reaction with N‐substituted isatilidenes

Abstract

A simple and efficient method, proceeding through a new mechanistic pathway, for the synthesis of spiro[indoline‐3,4‐thiopyrano[2.3‐b]indole derivatives have been developed by exploiting the reaction of thieno[2,3‐b]indole‐2,3‐dione with N‐substituted isatilidenes. The compounds synthesized have been screened for antibacterial activity. The generality of the reaction and mechanistic rationale are presented.

Stereoselective Synthesis of Dispirooxindoles Incorporating Pyrrolo[2,1-a]isoquinoline via [3+2] Cycloaddition of Azomethine Ylides with a Thiazolo[3,2-a]indole Dipolarophile

“…Our group reported the stereoselective synthesis of dispiro heterocycles by the [3+2] cycloaddition of isatin-derived azomethine ylides with a thiazolo[3,2- a ]indole derivative; 21 the latter prepared from thieno[2,3- b ]indole-2,3-dione 1 22 by methanol-promoted ring opening followed by a nucleophilic reaction with dimethyl acetylenedicarboxylate (Scheme 1 shows a representative example). On account of our continued interest in the chemistry of thieno[2,3- b ]indole-2,3-dione 23 and thiazolo[3,2- a ]indole derivative, 21 we made detailed investigations regarding [3+2] cycloaddition of 3a with azomethine ylide derived from isatins and 1,2,3,4-tetrahydroisoquinoline, which led to the synthesis of dispirooxindoles containing pyrrolo[2,1- a ]isoquinolines. Previous reports 24 25 26 on the direct synthesis of pyrrolo[2,1- a ]isoquinolines reveal that the regioselectivity of the reaction depends on the nature of the dipolarophile used as seen from Scheme 2 .…”

Update on thiopyran-fused heterocycle synthesis (2013–2024)

“…Tautomerization to enamine 32 and elimination of dimethyl oxalate 33 led to product 19 (Scheme 5). 17 Moghaddam and coworkers used different approaches to explore the possibility of nucleophilic addition of indoline-2thione. In 2013, they reported the synthesis of pentacyclic thiopyrano indole-annulated benzo-δ-sultone derivatives 37 and 38 in aqueous solution.…”

Development of spiro-3-indolin-2-one containing compounds of antiproliferative and anti-SARS-CoV-2 properties

“…1 ). Additionally, many synthetic spiro-indole analogs display considerable antimicrobial 21 – 24 , antitumor 8 and cholinesterase inhibitory properties 25 – 28 .

Figure 1 Natural spiro-indole containing compounds.

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