Browsing by Author "Khushboo Tiwari"

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Autocatalytic and DMSO-promoted regioselective synthesis of pyrimidine-fused quinolines from anilines and barbituric acids
(Royal Society of Chemistry, 2024) Pushpendra Yadav; Deblina Chatterjee; Suman Bhowmick; Khushboo Tiwari; Annapurna Awasthi; Dharmendra Kumar Tiwari
Autocatalytic and DMSO-participating regioselective synthesis of N,N-disubstituted pyrimido[4,5-b]quinoline-2,4(1H,3H)-diones from anilines and barbituric acids has been achieved. In this newly developed one-pot tandem reaction, DMSO serves as a solvent cum methine source. Additionally, barbituric acid plays a dual role by acting as a substrate and a catalyst, making this reaction an environmentally benign approach to accessing valuable heterocycles. This method offers an auto-catalytic, additive-free, and operationally simple approach with a wide substrate scope and excellent tolerance for various functional groups. Furthermore, a few controlled experiments were conducted to gain insight into the reaction mechanism. Moreover, large-scale experiments have further enriched this methodology. © 2024 The Royal Society of Chemistry.
Rhenium-Catalyzed C(sp2)-H Silylalkenylation of Arenes: An Anti-Markovnikov Linchpin Strategy
(American Chemical Society, 2025) Suman Bhowmick; Annapurna Awasthi; Khushboo Tiwari; Pushpendra Yadav; Dharmendra Kumar Tiwari
Re-catalyzed highly regio- and stereoselective o-C(sp2)-H silylalkenylation of arenes is reported using a directing group approach under ligand-, additive-, and base-free conditions. A series of imine directing groups (DGs) have been exploited on aromatic aldehydes to overcome de novo synthesis. This unique protocol allows us to access o-C-H activation of various heterocyclic moieties, including N-aryl 2-pyridones and arylpyridines. Sequential difunctionalization experiments have been performed. A series of mechanistic experiments have been carried out to gain mechanistic insight. © 2025 American Chemical Society.
Synthesis of 4-styrylquinolines via direct oxidative C3-alkenylation of anthranils under Pd(ii) catalysis
(Royal Society of Chemistry, 2024) Annapurna Awasthi; Khushboo Tiwari; Pushpendra Yadav; Suman Bhowmick; Dharmendra Kumar Tiwari
The palladium-catalyzed oxidative C3-alkenylation of anthranils (2,1-benzisoxazoles) with various styrenes has been successfully achieved. The C3-alkenylated anthranils were subsequently utilized in a [4+2]-cycloaddition with in situ generated α,β-unsaturated ketones leading to the synthesis of a diverse range of olefin-containing quinolines. Notably, this reaction exclusively yielded mono-alkenylated products with E-selectivity. The optimized catalytic conditions were compatible with a wide variety of substituted olefins and anthranils, forming various C3-alkenylated anthranils with good yields. To showcase the application of the present methodology, the C3-alkenylated anthranils have been employed as synthons to access a wide range of substituted quinolines. © 2024 The Royal Society of Chemistry.
Tf2O-mediated [4+2]-annulation of anthranils with 2-chloropyridines: enabling access to pyridoquinazolinones and euxylophoricine B
(Royal Society of Chemistry, 2024) Annapurna Awasthi; Khushboo Tiwari; Dharmendra Kumar Tiwari
We present an efficient approach for synthesizing pyridoquinazolinones in the presence of triflic anhydride utilizing anthranils and 2-chloropyridines as starting materials. In this process, Tf2O initially activates anthranils forming an electrophilic 1-((trifluoromethyl)sulfonyl)benzo[c]isoxazol-1-ium species. This species undergoes an in situ annulation reaction with 2-chloropyridines, resulting in therapeutically useful pyridoquinazolinones. The reaction is tolerant to various functional groups, allowing access to a wide range of substituted pyridoquinazolinones in good yields. Furthermore, the synthesis of euxylophoricine B, known to be an antitumor agent, was also achieved. © 2024 The Royal Society of Chemistry.