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Short Paper | Regular issue | Vol 102, No. 4, 2021, pp.705-722
Published online, 29th January, 2021
DOI: 10.3987/COM-20-14403
Synthesis of Pyrazolo[4,3-c]quinolines and the C-C Bond Cleavage during Reductive Cyclization

Nisha Devi, Antriksh Gupta, Raghuram Gujjarappa, Chandi C. Malakar,* and Virender Singh*

*Department of Chemistry, National Institute of Technology Manipur, Langol, Imphal-795004, Manipur, India


An efficient synthesis of o-nitrophenyl tethered pyrazole-4-carbaldehydes was achieved via Vilsmeier-Haack formylation of hydrazone derivatives which were subjected to Claisen-Schmidt condensation and Morita-Baylis-Hillman (MBH) reaction with various methyl ketones and activated alkenes respectively to generate the corresponding chalcones and MBH adducts. However, successive Fe-mediated reductive cyclization was followed by an unusual C-C bond cleavage which afforded the pyrazolo[4,3-c]quinolines devoid of diverse substituents at C-4 position.