Department of Chemistry

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Subject: search.filters.subject.Column chromatography

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Now showing 1 - 6 of 6
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    Tandem transformation of indazolones to quinazolinones through pd-catalyzed carbene insertion into an n–n bond
    (ACS, 2023-01) Shakuja, Rajeev
    Serendipitous and expedite transformation of 1-aryl- and 2-aryl-1,2-dihydro-3H-indazol-3-ones to 1,2-di(hetero)aryl- and 2,3-di(hetero)aryl-2,3-dihydroquinazolin-4(1H)-ones, respectively, was achieved in high efficiency by reacting them with aldehydic N-tosylhydrazones. The protocol proceeded through a cascade process involving base-mediated Pd-carbenoid generation by the decomposition of N-tosylhydrazones, nucleophilic attack of indazolone on the Pd-carbenoid complex, and intramolecular ring expansion via N–N bond cleavage. The utility of the strategy is demonstrated toward the synthesis of bioactive NPS 53574, a calcium receptor antagonist.
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    RH(III)-catalyzed fabrication of [4,3,1]-bridged azaheterocycles using quinone monoacetals
    (ACS, 2025-06) Sakhuja, Rajeev
    A rhodium-catalyzed annulation strategy for the fabrication of cyclohexanone-bridged indazolones and other related diazole-ones and diazine-ones was established using quionone monoacetals under mild conditions. On the other hand, the use of 4-hydroxy-4-methylcyclohexa-2,5-dienone under the optimized Rh-conditions produced an ortho-CAr-arylated product in moderate reactivity. Mechanistic studies suggested that the coupling proceeded via one-pot C–H activation-Michael/hetero-Michael additions into the enone moiety. Interestingly, the [4,3,1]-bridged-1,2-dihydro-3H-indazol-3-ones underwent unexpected migratory aromatization in acidic condition to produce 3-hydroxy-14H-benzo[c]indazolo[1,2-a]cinnolin-14-ones in high yields.
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    TEMPO-Mediated Synthesis of Indolyl/Imidazo[1,2-a]pyridinyl-Substituted para-Quinone Methides from Butylated Hydroxytoluene
    (ACS, 2021-11) Kumar, Anil
    A series of indolyl or imidazo[1,2-a]pyridinyl-substituted para-quinone methides (p-QMs) is prepared by a metal-free, TEMPO-mediated cross-dehydrogenative coupling of butylated hydroxytoluene (BHT) with indoles or imidazo[1,2-a]pyridines in good to high yields. Broad substrate scope with respect to indoles and imidazo[1,2-a]pyridines, good functional group tolerance, and acid/base-free conditions are advantageous feature of the developed protocol. The method was amenable for scale-up on the gram scale. Based on control experiments, a reaction mechanism is proposed to describe this transformation.
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    KPF6-Mediated Esterification and Amidation of Carboxylic Acids
    (ACS, 2022-01) Kumar, Anil
    A novel KPF6-promoted green method has been developed for the synthesis of esters and amides. A wide range of carboxylic acids and alcohols or amines worked well under the developed reaction conditions, thus providing good to excellent (61–98%) yields of the corresponding esters and amides. The method worked well with bioactive substrates such as cholesterol, levulinic acid, and linoleic acid. Wide substrate scope, operational simplicity, scalability, and sustainability make this protocol a practical and economically attractive approach for the preparation of ester and amides.
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    Investigation of the Reactivity of 1-Azido-3-iodobicyclo[1.1.1]pentane under “Click” Reaction Conditions
    (ACS, 2020-12) Grover, Nitika
    The bicyclo[1.1.1]pentane (BCP) unit is under scrutiny as a bioisostere in drug molecules. We employed methodologies for the synthesis of different BCP triazole building blocks from one precursor, 1-azido-3-iodobicyclo[1.1.1]pentane, by “click” reactions and integrated cycloaddition–Sonogashira coupling reactions. Thereby, we accessed 1,4-disubstituted triazoles, 5-iodo-1,4,5-trisubstituted triazoles, and 5-alkynylated 1,4,5-trisubstituted triazoles. This gives entry to the synthesis of multiply substituted BCP triazoles on either a modular or a one-pot basis. These methodologies were further utilized for appending porphyrin moieties onto the BCP core.
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    Reducing-Agent-Free Convergent Synthesis of Hydroxyimino-Decorated Tetracyclic Fused Cinnolines via RhIII-Catalyzed Annulation Using Nitroolefins
    (ACS, 2021-01) Sakhuja, Rajeev
    A mild Rh-catalyzed method was developed for the synthesis of hydroxyimino functionalized indazolo[1,2-a]cinnolines and phthalazino[2,3-a]cinnolines by reductive [4 + 2] annulation between 1-arylindazolones and 2-aryl-2,3-dihydrophthalazine-1,4-diones with varied nitroolefins. The targeted oxime decorated tetracyclic fused cinnolines were synthesized via sequential C–H activation/olefin insertion/reduction under reducing-agent-free conditions.