First synthesis and biological evaluation of indeno[2,1-e]pyrazolo[3,4-b]pyrazin-5-one and related derivatives

The synthesis of indeno[2,1-e]pyrazolo[3,4-b]pyrazin-5-one was achieved by intramolecular Friedel–Crafts reaction of the acid chloride 3-methyl-1,6-diphenyl-1H-pyrazolo[3,4-b] pyrazine-5-carboxylic acid chloride (4) using AlCl3 in boiling CS2. Compound 4 proved to be a versatile compound for the synthesis of several Indenopyrazolopyrazinone derivatives. The antibacterial and antifungal activities of selected derivatives were evaluated.

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► A new heterocyclic system indeno[2,1-e]pyrazolo[3,4-b]pyrazine was synthesized.
► Several derivatives of this heterocyclic system have been prepared.
► Selected derivatives were screened for their antibacterial and antifungal activities.
► Other utilities of the compounds prepared are under investigation.