Browsing by Author "Shamnad, A."

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    In Situ Generation and [3 + 2] Annulation Reactions of Propiolaldehyde?A Metal-Free, Cascade Route to Pyrazole and Bipyrazole Carboxaldehydes in One Pot
    (American Chemical Society, 2025) Sreelekha, M.K.; Shamnad, A.; Bhaskaran, R.P.; Babu, B.P.
    Propiolaldehyde, the most reactive yet less explored electrophilic acetylene, was generated in situ via a base-free Kornblum oxidation from propargyl tosylate and successfully intercepted with hydrazones affording pyrazole-4-carboxaldehyde in one-pot by a [3 + 2] annulation reaction. Further, the pyrazole-4-carboxaldehyde endured a unique cascade reaction with phenylhydrazine and propargyl tosylate, yielding synthetically challenging bipyrazole carboxaldehydes. The method is free of any metal catalyst, base, or additives and offers a convenient protocol to handle the reactive and volatile propiolaldehyde under ambient conditions. © 2025 American Chemical Society.
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    Metal-Free Bisamidation of N-Tosylhydrazones with Carboxylic Acids Promoted by Tetrabutylammonium Iodide and tert-Butyl Hydroperoxide
    (American Chemical Society, 2024) Shamnad, A.; Nayak, K.H.; Babu, B.P.
    A versatile reaction between N-tosylhydrazones and carboxylic acids to access bisamides is reported. This metal-free, room-temperature reaction was catalyzed by TBAI, while TBHP served as the oxidant. Broad substrate scope and good functional group tolerance are the key features of the strategy. Subsequent intramolecular N-arylation of suitably substituted bisamides readily afforded functionalized 3-indazolones. © 2024 American Chemical Society
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    Synthesis of 4H-Indazol-4-ones and Fused Pyrazoles via Copper-Catalyzed Annulation of Hydrazones with Cyclic Enones
    (John Wiley and Sons Inc, 2023) Nayak, K.H.; Bhaskaran, R.P.; Shamnad, A.; Babu, B.P.
    Herein, we report the synthesis of cyclic ketone-fused pyrazoles via [3+2] annulation reaction between hydrazones and cyclic enones (five-, six- and seven-membered) catalyzed by Cu(II) under aerobic conditions. These compounds were further functionalized by reactions such as Suzuki-Miyaura cross-coupling, Heck coupling, and Aldol reaction to afford diverse molecular scaffolds in good yield, selectivity and functional group tolerance. © 2023 Wiley-VCH GmbH.