The new facile and straightforward method for the synthesis of 4H-1,2,3-thiadiazolo[5,4-b]indoles and determination of their antiproliferative activity

• A new method for the synthesis of 1,2,3-thiadiazole and indole hybrid derivatives was proposed.
• Biological activity were evaluated through a series tests for the three representative compounds.
• Investigated compounds have shown anti-proliferative activity and potency to induce apoptosis.
• Biological behavior 1,2,3-thiadiazolo[5,4-b]indoles may be tuned by the nature of the substituents in their molecules.

A series of 4H-1,2,3-thiadiazolo[5,4-b]indoles were synthesized by novel tandem of oxidative cyclization of 3-alkoxycarbonylhydrazonoindoline-2-thiones, 1,5-H-shift and elimination of tert-butoxy(ethoxy)carbonyl group. The simple method for their modifications by the reactions with electrophilic agents were elaborated and as a result of the synthetic investigation a number of N-alkyl-, N-acyl- and N-sulfonyl-4H-1,2,3-thiadiazolo[5,4-b]indoles were prepared in good yields. Preliminary biological tests for the three examples of synthesized compounds with different substituents at the nitrogen atom indole ring have shown that the biological behavior of the investigated 1,2,3-thiadiazolo[5,4-b]indoles is substantially directed by this structural fragment.

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